Speed breeding by using shorter photoperiods to accelerate flowering and anticipating seed harvest in plants

Abstract

A speed breeding protocol is provided for to accelerate the flowering and harvest time of plants. Further embodiments include variation of the photoperiod time to optimize maturity. Additional embodiments include variation of the light source and variation of the distance of light source in relation to the plant canopy to optimize maturity. Further embodiments provide for plants that mature 60% earlier than plants growing in full-sun as a control. Yet further embodiments provide for a speed breeding protocol where the harvested immature seeds have increased germination rates when compared to controls.

Description

TITLESPEED BREEDING BY USING SHORTER PHOTOPERIODS TO ACCELERATE FLOWERING AND ANTICIPATING SEED HARVEST IN PLANTS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U. S. Provisional Application No.63 / 727,109, filed December 2, 2024, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Soybeans(*Glycine max* L. Merr.) are currently the most important crop in the world due to their widespread use and high oil and protein content (Yan, G. & R. Baidoo. 2018. Current Research Status of Heterodera glycines Resistance and Its Implication on Soybean Breeding. Engineering 4:534-541). Over the last two decades, world soybean production and harvested area have increased faster than other crops (Nagatoshi, Y. & Y. Fujita. 2019. Accelerating Soybean Breeding in a CO2-Supplemented Growth Chamber. Plant Cell Physiol. 60:77-84). This exponential growth in the crop has been driven by the application of different production techniques, one of which is genetical enhancement.

[0003] Plant breeding is one of the main elements for increasing agricultural production and ensuring global food security, in view of the growing population, in contrast to climate change that can negatively impact crops (See Atlin, G. N., J. E. Cairns & B. Das. 2017. Rapid breeding and varietal replacement are critical to adaptation of cropping systems in the developing world to climate change. Glob. Food Sec. 12:31-37 and Brown, PT. & K. Caldeira. 2017. Greater future global warming inferred from Earth’s recent energy budget. Nature 552:45-50). To enhance productivity and production stability, there is constant pressure to accelerate research and increase the rate of developing new soybean cultivars and traits within soybean genetic enhancement (Ghosh, S., A. et al., 2018. Speed breeding in growth chambers and glasshouses for crop breeding and model plant research. Nat. Protoc. 13:2944-2963), meaning individuals with specific and superior characteristics. However, the time between soybean generation advances remains a bottleneck for studies on the crop around the world (Nagatoshi & Fujita 2019). As soybean cultivation is limited to just one or two generations per year, techniques that reduce this time are essential.SUMMARY

[0004] One embodiment provides for a method of accelerating the development of a plant, comprising:an enclosed growth chamber having: at least one rack for holding one or more plants or plant parts potted in one or more containers; one or more light emitting diode (LED) lights situated above the one or more containers containing the plants, wherein the LED lights are contained on a bar or are individually hung above the plants or plant parts; and whereas the LED lights can be adjusted in a vertical position; allowing the LED lights to remain on continuously for at least an 8 hour photoperiod during each twenty-four hour period; and continuously adjusting the LED lights with the height of plant canopy, so that the distance between the LED light and plant canopy is at least 25 centimeters until the one or more plants reach a desired maturity and harvesting said plants. The containers could be for example, in individual pots or trays, and the containers could be made of materials including but not limited to plastic, natural fibers, clay, etc. Examples of substrates for the potting containers can include one or more of the following: soil, soilless mixes such as peat moss, coco coir, perlite, vermiculite, pine bark mixes (often with peat, sand, or perlite), and specialty mixes that incorporate ingredients like compost, composted yard waste, rice hulls, or specific soil pH needs. The desired maturity can be at least 60 days after emergence (DAE), but can also include but not be limited to, at least 67, 74 and 81 DAE. Another embodiment includes collecting immature or mature seed from said method and germinating said seed to produce a plant. The method further includes a reduction in at least 10, at least 11, at least 12, at least 13, at least 14, at least 15 and at least 16 days to flowering when compared to a plant grown in full-sun as a control.

[0005] Another embodiment provides for a method of accelerating harvest of plant, comprising: an enclosed growth chamber having: at least one rack for holding one or more plants or plant parts potted in one or more containers; one or more light emitting diode (LED) lights situated above the one or more containers containing the plants, wherein the LED lights are contained on a bar or are individually hung above the plants or plant parts; and whereas the LED lights can be adjusted in a vertical position; allowing the LED lights to remain on continuously for at least an 8 hour photoperiod during each twenty-four hour period; and continuously adjusting the LED lights with the height of plant canopy, so that the distance between the LED light and plant canopy is at least 25 centimeters until the one or more plants reaches a desired maturity.

[0006] Another embodiment provides for wherein said LED lights comprises at least 30 watts of power and at least 2700 lumens of luminous flux.

[0007] A further embodiment provides for wherein the LED light has a continuous intensity of at least 600, 700, 800, 900 or 1000 m-2 s-1.

[0008] A further embodiment provides for wherein the racks are arranged linearly and / or vertically. Thus, depending on a facility’s layout, the racks can be both built out linearly and vertically depending on the height of the facility.

[0009] A further embodiment provides for at least a five-sided, or at least a six-sided growth chamber which is enclosed with individually or in combination with fabric, glass, metal, plastic, drywall, or wood, on all sides (top, sides and when applicable, bottom). This embodiment is the typical rectangular or square shaped growth chamber, however, the enclosed growth chamber can have more or less sides depending on the configuring shape. The growth chamber can be built into an area (i.e., such as a walk-in growth chamber, which are well-known in the art), a stand-alone growth chamber having, or a moveable growth chamber having feet and / or wheels, for example. The growth chamber, being built with one or more types of materials herein, would be built to control the amount of external light to be able to enter the chamber. Another embodiment provides for where the fabric consists of a double layer of non-woven fabric. The growth chamber is an enclosure that provides for a more controlled environment for growing plants and plant parts as compared to growing outside in a field, for example.

[0010] A further embodiment provides for wherein said plant comprises alfalfa, apple, apricot, artichoke, asparagus, avocado, banana, barley, beans, beet, blackberry, blueberry, Brassica, broccoli, brussel sprouts, cabbage, canola, carrot, cassava, cauliflower, a cereal, celery, cherry, citrus, Clementine, coffee, com, cotton, cucumber, eggplant, endive, eucalyptus, figs, grape, grapefruit, groundnuts, ground cherry, kiwifruit, lettuce, leek, lemon, lime, pine, maize, mango, melon, millet, mushroom, nut oat, okra, onion, orange, an ornamental plant or flower or tree, papaya, parsley, pea, peach, peanut, pepper, persimmon, pineapple, plantain, plum, pomegranate, potato, pumpkin, radicchio, radish, rapeseed, raspberry, rice, rye, sorghum, soy, soybean, spinach, strawberry, sugar beet, sugarcane, sunflower, sweet potato, tangerine, tea, tobacco, tomato, a vine, watermelon, wheat, yams and zucchini, or a part (i.e., plant part) thereof. “Plant part” refers to parts of a plant including leaves, seed, stems, roots, flowers or flower parts, fruits, pollen, egg cells, zygotes, seeds, bud, embryo, cuttings, cell or tissue cultures, or any other part or product of a plant. A “plant part” can comprise a part of plant such as a root, stem, leaf, flower bud, or embryo.

[0011] A further embodiment provides for wherein the days to maturity of said plant is reduced at least 60% when compared to a plant grown in full sun for at least an eight-hour photoperiod.BRIEF DESCRIPTION OF THE FIGURES

[0012] FIGs. R1a-c shows the areas of adaptation of soybean cultivars BRS546, BRS531 and BRS8381 in Brazil.

[0013] FIG. SI shows the sketch of the random distribution of the pots in the growth chambers and benches following a completely randomized design for the different photoperiods.

[0014] FIGs. S2a-b show (a) the structure of the growth chamber used in the study (3.0 m in length, 1.2 m in width, and 2.0 m in height) (b) and a side view of the growth chamber with the distributed pots.

[0015] FIG. S3 shows the duration of daylight in the city of Trindade, state of Goias, throughout the year 2022.

[0016] FIGs. S4a-e shows the characterization of the distribution of LED lamps in the growth chambers during the study.

[0017] FIGs. S5a-d shows the characterization of the spectral quality in the growth chambers in the photoperiod 08 h (a), 10 h, (b) 12 h (c) and the luminosity inside the greenhouse (d).

[0018] FIG. S6 shows an image of the leaves used for leaf area determination using the ImageJ program alongside a segmented straight line in centimeters (cm) for use as a scale and program calibration.

[0019] FIGs. S7a-1 shows the leaf area (LA), root length (RL), root dry mass (RDM - labeled as MSR in FIGs. S7g-i) and root volume (RV) of soybean plants of different cultivars and development cycles as a function of different photoperiods and measurement seasons.

[0020] FIGs. S8a-c shows the number of flowers emitted daily by different soybean cultivars during the reproductive period under the effect of different photoperiods.

[0021] FIGs. S9a-b shows the principal component analysis (PCA) for indicators related to the harvesting of immature seeds of soybean plants of different cultivars under the effect of different photoperiods and different harvest seasons.

[0022] FIG. S10 shows the soybean plant development under the effect of different photoperiods, 8, 10 and 12 hours and full sun, at 23 days after planting (DAP) in controlled conditions in a greenhouse and growth chamber.

[0023] FIG. Sil shows the soybean plant development under the effect of different photoperiods at 40 days after planting (DAP) in controlled conditions in a greenhouse and growth chamber.

[0024] FIG. S12 shows the soybean plant development under the effect of different photoperiods at 66 days after planting (DAP) (1st harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0025] FIG. S13 shows the soybean plant development under the effect of different photoperiods at 73 days after planting (DAP) (2nd harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0026] FIG. S14 shows the soybean plant development under the effect of different photoperiods at 80 days after planting (DAP) (3rd harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0027] FIG. S15 shows the soybean plant development under the effect of different photoperiods at 87 days after planting (DAP) (4th harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0028] FIG. S16 shows the seeds of soybean plants under the effect of different photoperiods collected at 66 days after planting (DAP) (1st harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0029] FIG. S17 shows the seeds of soybean plants under the effect of different photoperiods collected at 73 days after planting (DAP) (2nd harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0030] FIG. S18 shows the seeds of soybean plants under the effect of different photoperiods collected at 80 days after planting (DAP) (3rd harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0031] FIG. S19 shows the seeds of soybean plants under the effect of different photoperiods collected at 87 days after planting (DAP) (4th harvest and evaluation) in controlled conditions in a greenhouse and growth chamber.

[0032] FIGs. S20A-C show (A) Taschibra® LED lamps with 30W of power and 2,700 lumens of luminous flux. (B) Distance between the lamps and the plant canopy. (C) Distribution of luminous intensity in μmol m⁻² s⁻¹ on 30 x 25 cm Grids.

[0033] FIGs. S21 A-B show a 3D illustration of the structure. (A) Distribution of the LED lamps in the structure. (B) Illustration of the worm screw bar that allows height adjustment.

[0034] FIG. S22 shows the distribution of the pots inside the growth chamber.

[0035] FIG. S23 shows the timeline of the speed breeding protocol in soybean.

[0036] FIGs. la-1 show plant height (PH), aerial part dry mass (APDM - but shown as MSPA on the graphs), number of pods (NP), and number of seeds (NS) of soybean plants of different cultivars and development cycles as a function of different photoperiods and measurement.

[0037] FIG. 2 shows the duration of the vegetative period and flowering period during the reproductive phase of different soybean cultivars under the effect of different photoperiods.

[0038] FIGs. 3a-c show the number of flowers emitted during the reproductive period by soybean plants of early (a), semi-early (b) and late (c) cultivars under the effect of different photoperiods.

[0039] FIGs. 4a-b show the efficiency of the artificial hybridization process (a) and number of seeds per pod (b) obtained after artificial hybridization in flowers from different soybean cultivars under the effect of different photoperiods.

[0040] FIGs. 5a-i show the percentage of emergence (a, b, c), seed weight (PS) (d, e, f) and seedling weight (SW) (g, h, i) from soybean plants under the effect of different photoperiods and different harvest seasons.

[0041] FIGs. 6a-b show the principal component analysis (PCA) for biometric (a) and physiological indicators related to gas exchange and photosynthesis (b) of soybean plants of different cultivars under the effect of different photoperiods and different measurement seasons.

[0042] FIGs. 7a-b shows the Pearson correlations represented in Heatmap obtained between the biometric (a) and physiological (b) variables of soybean cultivars under the effect of different photoperiods and measurement seasons.DETAILED DESCRIPTION

[0043] On the global stage, Brazil is currently the largest producer of soybeans, and the crop has become one of the main sources of income in agribusiness. In Brazil, soy occupies approximately 56% of the total area used for summer crops (Conab 2022). This represents a cultivated area of around 43.4 million hectares, resulting in an average grain yield of 3,536 kg ha-1 in the 2022 / 23 harvest (Conab 2022). The exponential growth of soybeans is due to their multifaceted characteristics, being a source of oil and protein, in addition, soybeans have recently emerged as a renewable and sustainable resource for biodiesel production (Woyann et al. 2019).

[0044] Its versatility and economic importance to Brazilian agribusiness is responsible for driving a wide range of genomic tools and resources in the search for increasingly productive plants (Nagatoshi & Fujita 2019). Despite progress in agriculture, forecasts estimate that the sector will face a number of challenges, especially in countries with a tropical climate such as Brazil (Borjas-Ventura et al. 2019). Estimates of rising temperatures and reduced rainfall further increase concerns and highlight the need to search for cultivars that are resistant to these changes (Marengo et al. 2017, Borjas-Ventura et al. 2019). These forecasts estimate that current annual growth rates in production volume are inadequate to meet future global demand for food (Harrison et al. 2021).

[0045] The efforts of breeding programs are aimed at generating more productive plants that are better adapted to adverse conditions, and most of the tools needed to develop more adapted cultivars are already in hand (Atlin et al. 2017). However, the speed with which new cultivars are launched on the market is very important to have answers to these challenges, and the time needed for this to happen is a bottleneck for plant breeding (Watson et al. 2018, Nagatoshi & Fujita 2019).

[0046] Soybean cultivation is currently limited to just 1 cycle per year under field conditions and the use of protected cultivation allows up to 3 generations per year. Consequently, the creation of new and advanced cultivars takes several years (Nagatoshi & Fujita 2019, Harrison et al. 2021). To reduce production time and speed up research, factors such as light intensity, quality and duration,as well as high CO2 concentrations and temperature, combined with early seed harvesting, are exploited in growth chambers and greenhouses (Nagatoshi & Fujita 2019, Yang et al. 2019, Watson et al. 2018, Ghosh et al. 2018). These factors have been speeding up various physiological processes in plants, especially flowering, allowing generation lead times to be reduced (Samineni et al. 2020).

[0047] However, although the use of techniques to speed up the cycle has enabled great advances, Wanga et al. (2021) point out that the technology requires facilities that require large investments. With this in mind, this work aims to describe how a low-cost growth chamber for growing soybeans can be built using LED (light-emitting diode) lamps and the protocol that makes it possible to speed up the soybean crop cycle.

[0048] In order to reduce production time and speed up research, various techniques have been explored for the rapid generation advance or “speed breeding” (SB), which seeks to shorten the crop cycle by manipulating environmental conditions to maximize the rate of plant development and anticipate flowering and, consequently, speed up its cycle (Harrison, D., et al., 2021. Effect of light wavelength on soybean growth and development in a context of speed breeding. Crop Sci. 61:917-928). SB is carried out by manipulating factors such as light intensity, quality and duration, as well as high CO₂ concentrations and temperature, combined with early seed harvesting (See Watson, A., G., et al., 2018. Speed breeding is a powerful tool to accelerate crop research and breeding. Nat. Plants 4:23-29 and Wanga, M. A., et al., 2021. Opportunities and challenges of speed breeding: Areview. Plant Breed. 140:185-194).

[0049] SB protocols make it possible to optimize the allocation of equipment and space, the allocation of human resources, and to advance observations that prevent the cost of products other than those desired, in addition to creating improved cultivars in a shorter space of time and speeding up the selection of new traits (Wanga et al. 2021). SB has proven to be efficient in long-day crops such as wheat, barley, canola, chickpeas and short-day plants such as peanuts (See O’Connor, D. J., et al., 2013. Development and Application of Speed Breeding Technologies in a Commercial Peanut Breeding Program. Peanut Sci. 40:107-114., Watson et al. 2018). For short-day crops such as soybeans, a protocol has recently been described that allows up to five generations to be obtained per year (Jahne et al. 2020), compared to two to three generations in the field in Europe. According to the authors, the method consists of using a ten-hour photoperiod with a blue length LED light source.

[0050] The availability of studies using fast generation advance methods in soybean breeding is still limited. In addition, no studies have been reported on the effect of photoperiod on differentmaturation groups of Brazilian commercial cultivars, in order to speed up their cycle and enable an efficient SB technique to be developed.The importance of Soybean

[0051] Soybeans (Glycine max (L.) Merrill) are the most important crop in Brazil and worldwide, being an important source of vitamins and minerals (See Kramer, C. M., et al., 2014. Vitamin E levels in soybean (Glycine max (L.) Merr.) expressing a p-hydroxyphenylpyruvate gene from oat (Avena sativa L.). J Agric. Food Chem. 62:3453-3457 and Biel, W., D. et al., 2018. Content of minerals in soybean seeds as influenced by farming system, variety and row spacing. J. Elem. 23:863-873), used both in the human diet and in animal feed (Maeta et al. 2022, Nakamori 2022, Saleh et al. 2022). In addition to being used for oil and in natura consumption, soybeans are also used as a raw material for the veterinary (Vandresen, G. & M. R. Farias. 2018. Efficacy of hydrolyzed soy dog food and homemade food with original protein in the control of food-induced atopic dermatitis in dogs. Pesq. Vet. Bras. 38: 1389-1393; Vieyra-Alberto, R., et al., 2022. Effect of soybean grain (Glycine max L.) supplementation on the production and fatty acid profile in milk of grazing cows in the dry tropics of Mexico. Trop. Anim. Health Prod. 54:52) and pharmaceutical industries (Prado, F. G., et al., 2022. Enhancing the recovery of bioactive compounds of soybean fermented with Rhizopus oligosporus using supercritical CO2: Antioxidant, anti-inflammatory, and oxidative proprieties of the resulting extract. J. Fungi 8:1065), paints and plastics (Swain, S. N., et al., 2004. Biodegradable soy-based plastics: Opportunities and challenges. J. Polym. Environ. 12:35-42 and Brentin, R. P. 2014. Soy-Based Chemicals and Materials: Growing the Value Chain, p. 1-23. In R. P. Bretin (ed.), Soy-Based Chemicals and Materials. Michigan, Omni Tech International, 403p), cosmetics (Wagas et al. 2015) and biodiesel production (Mourad, A. L. & A. Walter. 2011. The energy balance of soybean biodiesel in Brazil: a case study. Biofuel Bioprod. Biorefin. 5:185-197; Mariano, G., et al., 2014. Production of biodiesel with seed soybean and supercritical ethanol. J. Sustain. Bioenergy Syst. 4:128-135; Colombo, K., et al., 2019. Production of biodiesel from Soybean Oil and Methanol, catalyzed by calcium oxide in a recycle reactor. S. Afr. J. Chem. Eng. 28:19-25; and Onyenze et al. 2021).

[0052] Brazil is the world's leading soybean producer, followed by the United States, and together they produce around 70% of all global production (IPAD. 2023. Soybean 2022. International Production Assessment Division / USDA). In the last harvest (2021 / 22), Brazil alone produced 125,549 tons on 41,492 hectares (Conab. 2022. Acompanhamento da Safra Brasileira de Graos. CONAB: COMPANHIANACIONAL DE ABASTECIMENTO, Brasilia, DF, v. 10, safra 2022 / 23, n. 3, terceiro levantamento), accounting for almost 40% of world production. For the next harvest (2022 / 23) it is estimated that there will be a 4.6% increase in the planted area, with a 22.2%increase in national production (Conab 2022), due to the growing increase in productivity. The productivity of the soybean crop has been gradually increased over the years by advances in genetical enhancement processes (Ghosh et al. 2018; Hickey, L. T., et al., 2019. Breeding crops to feed 10 billion. Nat. Biotechnol. 37:744-754; Nagatoshi & Fujita 2019; Jahne, F., et al., 2020. Speed breeding short-day crops by LED-controlled light schemes. Theor. AppL Genet. 133:2335-2342; and Harrison etal. 2021). The Center- West region is currently responsible for 54.3% of national soybean production, and the state of Goias has one of the best national productivity figures, with 3,700 kg ha⁻¹ (Conab 2022).Photoperiodism

[0053] Photoperiodism refers to plant’s responses to photoperiod, i.e. the length of the day. Work on photoperiodism in soybean plants has been going on since the beginning of the 20th century, when the sensitivity of soybeans, a short-day plant, to the duration of the day was widely described by Garner & Allard (1920), following some work on artificial lighting in other crops (Schiibeler 1880, MacDougal 1903).

[0054] Plants depend on sunlight as a source of energy, so they need to detect the intensity, quality and direction of this critical environmental factor and respond appropriately, optimizing their growth and development (Batschauer 1999). The perception of light is carried out by various photoreceptors, including phytochromes, blue / ultraviolet (UV)-A, and UV-B photoreceptors (Batschauer 1999, Smith 2000).

[0055] Understanding the sensitivity of different soybean cultivars to photoperiod has allowed breeders to develop suitable cultivars for regions with different latitudes, especially for environments with long photoperiods (Johnson et al. 1960, Byth 1968, Wu et al. 2015, Ort et al.2022). The first soybean cultivars planted in Brazil were brought from the United States (Cattelan & Dall’Agnol 2018).

[0056] Cultivars originating from temperate climates, when grown near the equator, i.e., under conditions with longer photoperiods, have a shorter growth cycle, reducing growth and productivity (Hartwig & Kiihl 1979, Bortoluzzi et al. 2021). Furthermore, at the same latitude, changes in photoperiod can occur due to the season of sowing and, in addition, the critical photoperiod varies between different cultivars and even between plants with different degrees of maturity (Thomas & Raper 1983, Hadley et al. 1984, Ort et al. 2022).

[0057] Photoperiodic sensitivity and the time it takes for plants to reach physiological maturity are crucial for the adaptation of soybean plants in a given region. Among the main factors affected by photoperiodism, flowering stands out, as it is directly related to plant yield. Flower induction promotes the differentiation of vegetative structures into reproductive ones which, in addition todetermining the final growth of the plants, also affects the productivity of the crop (Major et al. 1975).

[0058] Continuous studies by breeders have enabled highly productive cultivars to be adapted to tropical regions such as Brazil (Spehar 1994, 1995, Urben Filho & Souza 1993, Xu et al. 2013). Different photosensitive genes responsible for controlling flowering time have already been identified in soybean plants (Cober et al. 2010, Xu et al. 2015, Cao et al. 2017, Samanfar et al. 2017, Han et al. 2019). Understanding their molecular bases and their interactions with the environment is necessary to determine genotypic combinations and provide for the insertion of highly productive cultivars in the cultivation season of a given region (Watanabe et al. 2012, Huang & Nusinow 2016, Bu e / aZ. 2021).Speed Breeding

[0059] Genetical enhancement requires i) selecting genitors with traits of interest; ii) crossing the selected genitors to develop progenies; iii) confirming the presence of the target traits and selecting the best progenies; and iv) cultivation of selected progenies in different environments (Shimelis & Laing 2012). With conventional breeding, soybeans are cultivated with 1 to 2 cycles per year, taking 15 to 20 years from crossing to the launch of the cultivar (Sinegovskaya 2021). Thus, the main limiting factor in genetic enhancement is still the crop's cultivation time.

[0060] Breeding techniques aimed at obtaining new cultivars in a shorter time have been explored. Among these new methodologies, speed breeding (SB) stands out, aiming for the rapid generation advance. SB seeks to shorten the crop cycle by manipulating environmental conditions to maximize the rate of plant development and anticipate flowering, and consequently speed up the cycle (Harrison et al. 2021).

[0061] The first studies carried out with SB were based on an experiment carried out by the Advanced Life Support program of the US National Aeronautics and Space Administration (NASA), with the first cultivation of plants under extended light conditions (Rowell et al. 1999). Subsequently, Hickey et al. (2009) used prolonged photoperiods with low-pressure sodium lamps under controlled conditions to evaluate the expression of dormancy in wheat grains (Triticum aestivum L.). The authors found that the use of artificial lighting to extend the photoperiod and controlled temperature accelerated the germination rate of wheat plant seeds until maturity.

[0062] O’Connor et al. (2013) observed that SB reduced the time to full maturation from 145 to 89 days in A. hypogaea plants under continuous light conditions (24 h) with 450-watt photosynthetically active radiation lamps and a daily temperature of 28 / 17°C (max / min). This allowed peanut plants to reach inbreeding of the F2, F3, and F4 generations in less than 12 months,and potentially drastically reduces the development of the first cross for commercial release of peanut cultivars by around six to seven years (O'Connor et al. 2013).

[0063] Gosh et al. (2018) reported that eleven species evaluated (T. aesivum. T. durum, Hordeum vulgare, Brassica napus, B. rapa, B. oleracea, Pisum sativum, Lathyrus sativus, Brachypodium distachyon, Chenopodium quinoa e Avena sativd) reduced the time to flowering by up to 28.4%. Increasing the photoperiod of these plants by 6 h, from 16 h to 22 h, with a temperature of 22 / 17°C (day / night). Since then, various other studies have been carried out on different crops, and SB has been shown to be effective on long-day crops such as wheat, barley, canola, chickpeas, peas, lentils and sugar beet, on short-day plants such as peanuts, soybeans, sorghum, rice, millet, sugar cane and cotton, and on neutral-day plants such as potatoes and tomatoes (see for example, Zheng et al. (2013), Rizal et al. (2014), Liu et al. (2016), Mobini & Warkentin (2016), Stetter et al. (2016), Saxena et al. (2019), Jahne et al. (2020), Gonzalez-Barrios et al. (2021), Vikas et al. (2021) and Edet & Ishii (2022)).

[0064] The SB technique accelerates flowering by providing a shorter night period for long-day and day -neutral plants (Watson et al. 2018, Gosh et al. 2018) and a longer night period for short-day plants (Jahne et al. 2020, Bhatta et al. 2021), such as soybeans. Soybeans, in particular, as well as being short-day crops, are highly sensitive to photoperiod. However, differences between the effects of photoperiod on the duration of soybean development stages can be different between early and late cultivars. This is because early maturing soybeans are less sensitive to photoperiod than late maturing cultivars. Late maturing cultivars have a longer interval between the growth stages and flowering, and between flowering and physiological maturation, and are more sensitive to photoperiod (Major 1980, Harrison et al. 2021).

[0065] The first associations between photoperiod (duration of the day) and soybean flowering were verified by Garner & Allard (1920, 1930). The authors observed changes in the vegetative development of the plants according to the strain and region in which the plants were grown, allowing the selection of strains with less sensitivity to photoperiod and a greater likelihood of successful growth (Garner & Allard 1930). Initially, only mature soybean seeds were capable of generating viable seeds (Adams & Rinne 1981). Subsequently, Rosenberg & Rinne (1987) found that early mature seeds, harvested 35 days after flowering and dried for 7 days, had similar biochemical responses and germination rates to mature seeds (harvested 70 days after flowering).

[0066] With the advance of conventional breeding, the embryo culture technique allowed the use of embryos at approximately 18 days after flowering, reducing the length of the cycle from 130-140 days to 65-70 days (Roumet & Morin 1997) and has been used to this day for different crops(Zheng et al. 2013, Rizal et al. 2014, Liu et al. 2016, Tanaka et al. 2016, Gosh et al. 2018, Hickey et al. 2019, Samineni et al. 2020, Fang et al. 2021).

[0067] SB has been carried out by manipulating factors such as light intensity, quality and duration, as well as high CO2 concentrations and temperature, combined with early seed harvesting. Jahne et al. (2020) found that adjusting the photoperiod to 10 h of light using a light spectrum enriched with blue light and deprived of far-red light, with a constant temperature of 28°C and relative humidity between 80 and 100%, facilitated the growth of soybean plants, which flowered approximately 23 days after sowing and matured in 77 days, making it possible to obtain up to five generations per year. Also evaluating the quality of light, Harrison et al. (2021) observed that the use of LED lights containing 80% red light and 20% blue light (1018 μmol m⁻² s⁻¹), with a 12 h photoperiod and a temperature of 29 / 27°C (day / night) induced flowering in soybean plants, reducing the crop cycle by between 56 and 66 days when compared to field conditions.

[0068] Supplementation with carbon dioxide (CO2, > 400 μmol mol−1), combined with adequate lighting (fluorescent lamps, 220 μmol m⁻² s⁻¹), a 14 h photoperiod and a temperature of 30 / 25°C (day / night) also allowed the soybean cycle to be reduced from 102-132 days in the field to just 70 days (Nagatoshi & Fujita 2019). According to the authors, the method uses CO2 to promote plant growth and yield, the right light and temperature conditions to reduce flowering and harvesting days, and sowing immature seeds to shorten the reproductive period.

[0069] The use of immature seeds usually requires drying in order to achieve high germinability. Fang et al. (2021) evaluated soybean progenies from different ecological regions and found that the integrated system of generation advance outside the place of origin and the method of sowing fresh seeds under ambient conditions made it possible to shorten each generation by the 7 to 10 days needed for the seeds to dry. The authors reported that locations with lower latitude and higher temperatures can be used as efficient, low-cost off-site summer nursery patterns associated with marker-assisted selection (Fang etal. 2021).

[0070] In addition to plant growth conditions, costs are important for the viability of crop breeding. Gallino et al. (2022) adapted low-cost facilities using the cold room with controlled conditions (fluorescent lamps with a 12 h photoperiod of luminosity (350 μmol m⁻² s⁻¹) and temperature set at 24°C, and found that, together with the controlled dehydration of immature seeds in intact pods, it is possible to reduce the duration of the total soybean cycle to 60 days, compared to a minimum of 140 days under field conditions, without affecting plant vigor. The study was carried out with different early-maturing, medium-maturing and late-maturing soybean lines using the SB method (also known as Rapid Generation Advance, RGA), which allows up to 5 annual cycles to beobtained, instead of the 1-2 generations currently possible in field and greenhouse conditions for all the lines evaluated (Gallino et al. 2022).EXAMPLESMaterials and MethodsBuilding the Growth Chamber

[0071] Protected environments are important tools for adopting techniques to speed up the crop cycle, enabling better control of environmental conditions, as well as allowing easy modifications to conditions that can influence the acceleration of the crop cycle (Wanga et al. 2021). Among these factors, light is one of the main factors influencing plant growth and development. In protected environments, LED lamps are currently more widely used because they have approximately 5% energy loss in the form of heat, which is much less than incandescent and fluorescent lamps (Goto et al. 2012). This way, as well as having low heating around their structure, they also enable lower energy costs because they need less power to produce the same luminous flux, and have a longer lifespan when compared to the others.

[0072] In the growth chamber measuring 1.2 x 3.0 m in width and length respectively, 50 units of Taschibra® brand LED lamps with 30W of power and 2700 lumens of luminous flux (FIG. 1A) were used. Under these conditions it is possible to obtain a more homogeneous light distribution at a height of 25 cm from the plant, reaching a light intensity of at least 550, 600, 650, 700, 800, 900 or 1,000 μmol m−2s−1(FIG. IB). 05 cm was not used from the two ends of the structure due to the low light intensity available (FIG. 1C and see also FIGs. S4a-e for the distribution of the lamps). FIGs. S5a-d show the characterization of the spectral quality in the growth chambers in the photoperiod 08 h (a), 10 h, (b) 12 h (c) and the luminosity inside the greenhouse (d). FIGs. S20A-C show (A) Taschibra® LED lamps with 30W of power and 2,700 lumens of luminous flux. (B) Distance between the lamps and the plant canopy. (C) Distribution of luminous intensity in μmol m⁻² s⁻¹ on 30 x 25 cm Grids.

[0073] In order to ensure that the height of the lamps in relation to the plant canopy was maintained throughout the crop’s growth, at least every 2 days, the height of the luminaires in relation to the plant canopy was adjusted. To control the height of the aforementioned structure, metal worm bars were placed at the four ends of the structure, ensuring that the luminaires could be moved as the crop grows (FIG. 2).

[0074] In addition to light intensity, another factor that influences the development and cycle of the soybean crop is photoperiod. A photoperiod of 08 h was used herein. It is important to note that in order to ensure that there was no influence from external light, all five sides of the growth chamber structure was enclosed with a double layer of non-woven fabric (TNT) weighing 120 grams.However, it is important to note that variations of the growth chamber can be used. For example, five-sided enclosed growth chamber which is enclosed with individually or a combination of fabric, glass, metal, plastic, drywall, or wood, on all four sides. The growth chamber can be built into an area (i.e., such as a walk-in growth chamber, which are well-known in the art), a stand-alone growth chamber having, or a moveable growth chamber having feet and / or wheels, for example. In addition, to allow for maintenance inside the growth chamber structure, hook and loop straps were used on the Velcro® fasteners at the ends of the TNT and the metal structure.

[0075] A speed breeding protocol was developed and validated, using different photoperiods in order to accelerate the flowering of different soybean maturation groups, as well as evaluating the feasibility of harvesting immature seeds to obtain a new generation of plants.A. Location of the study area and experimental design

[0076] The study was conducted at the BASF Research Station in Trindade, Goias (S16o37'14.01", W49°32'58.2", 720 m altitude) in a completely randomized design (CRD) (FIG. SI) in a 4 x 3 factorial scheme, with 18 repetitions. A greenhouse was used to cultivate the plants in full sun (control) and growth chambers for the different photoperiod conditions. The growth chambers consisted of a metal structure (3.00 m in length x 1.20 m in width x 2.00 m in height) with closed sides to prevent light from entering and leaving (FIGs. S2a-b). The first factor corresponded to different photoperiods: 08, 10, and 12 hours of daylight-1, and a control in full sun. The second factor corresponded to three soybean cultivars from different maturation groups (early - BRS546; semi-early - BRS531; and late - BRS8381). The experiment was planted on May 25, 2022, in the city of Trindade, Goias, and the duration of the day or photoperiod in full sun during the experiment is shown in FIG. S3 and the characteristics of the soybean cultivars used in Table SI and FIGs. R1a-c.Table SI: Characteristics of Soybean Cultivars BRS546, BRS531 and BRS8381Soybean CultivarBRS546 BRS531 BRS8381Maturity Group 6.0 ■ Maturity Group 7.3 ■ Maturity Group 8.3 Growth: Growth: Growth undetermined ■ undetermined ■ semi-determined Purple flower: White flower: Purple flower Brown pubescence ■ Brown pubescence ■ Gray pubescence Average cycle: 95 - 109 days: Average cycle: 106 - 124 days: Average cycle: 112 - 130 daysB. Cultivation environment

[0077] The soybean plants were cultivated in 8-liter plastic pots containing a substrate formed by the mixture of soil from a Dystroferric Red LATOSOL collected from the subsurface and Bioplant plus® substrate in a 1:1 ratio. To prepare 400 L of substrate (200 L of soil and 200 L of Bioplant plus®), 600 g of calcitic limestone (36% CaO and 3% MgO), 150 g of quicklime and 2,200 g of formulated fertilizer (04-30-10) were added and mixed homogeneously. The physicochemical characteristics of the substrate after preparation are shown in Table 2.Table 2. Chemical attributes and textural characterization of the substrate used as a growth medium for soybean plants in the greenhouse and growth chambers.AttributesaUnit Value Attributes Unit Value pH (CaC12) - 5.2 Manganese (Mn) mg dm333 Calcium (Ca) cmoL dm38.4 Zinc (Zn) mg dm34.9 Magnesium (Mg) cmoL dm30.8dSOM g kg158 Aluminum (Al) cmoL dm30.0eSat. Al (m%) % 0.0 Potential acidity (H+ Al) cmoL dm33.8fBase sat. (V%) % 72bCEC cmoL dm313.55gR. Ca / Mg - 10.5cPhosphorus (P) mg dm385.0eSat. Ca / CEC % 62.2 Potassium (K) mg dm3214eSat. Mg / CEC % 5.9 Sulphur (S) mg dm318.0eSat. H+A1 / CEC % 28.1 Sodium (Na) mg dm32.0eSat. K / CEC % 4.1 Boron (B) mg dm30.27 Clay % 20.0 Copper (Cu) mg dm30.40 Silt % 6.0 Iron (Fe) mg dm391 Sand % 74.0aAnalysis carried out according to Teixeira et al. (2017) - Manual of soil analysis methods;bCEC: Cation exchange capacity;cAvailable phosphorus determined by Mehlich-1 extractor;dSOM: Soil organic matter;eSat: Saturation = (Ca or Mg or Al or H+Al or K / CEC) x 100;fBase sat.: Base saturation = (Ca + Mg + K + Na) / CEC) x 100;gR.: ratio.

[0078] Three seeds were sown per pot under controlled conditions in the growth chamber and in full sun in the greenhouse. FIG. S22 shows the distribution of the pots in the growth chamber. Thinning was carried out on the seventh day after emergence, leaving two plants per pot. The temperature of the greenhouse was kept at 40°C and relative humidity at 40%. The luminosity in the growth chambers was controlled by providing a constant photon flux density of 550-650 pmolm2s ' using light-emitting diode reflectors (LEDs, Taschibra®, Brazil) with 30W of power and 2,700 lumens (FIG. S4), however, a constant photo flux density of 700, 800, 900, and 1000 μmol m⁻² s⁻¹ have also been used, the characteristics of which are shown in Fig. S5. Photosynthetically active radiation was determined using the PAR sensor (APG-SQ-316, Apogee, North Logan, UT, USA) and light quality was determined using the LI 180 spectroradiometer (LLCOR, NE, USA). Full sun was monitored at 08:00 AM, 10:00 AM, 12:00 PM, 2:00 PM, and 4:00 PM. The data obtained was integrated using the following equation: DLI = (A*B*3600 / l,000,000). Where A = measured value in μmol m⁻² s⁻¹, B = Number of hours of photoperiod; 3600 is the time interval between measurements in seconds, and 1,000,000 is the conversion from 1 pmol to molar (Specian 2013).

[0079] Light accumulation - DLI( / L / / 7)' Light Integral) during the photoperiod was 17.3, 21.6, 25.9, and 42.3 mol m−2day−1respectively, for the 08, 10, 12 h and full sun photoperiods.

[0080] Fertilization throughout the experiment was carried out through fertigation, as described in Table 3.Table 3. Fertilizers used in the periodic fertigation of soybean plants throughout the study.Nutrients and Concentration DoseCommercial Name Weekday (%) (g plant ')N (18%), P2O5 (18%), K2O (18%), SMultipurpose 0.45(1%), B (0.03%) Zn (0.1%)DripSol Micro B (17%) 0.048 MondayRoyalfex Fe (6%) 0.037NitraBor Ca (18%), B (0.3%), N (15.4%) 0.18 TuesdayUrea N (46%) 0.2Ultra Copper K2O(1%), S (10.7%), Cu (24%) 0.009Ultra Manganese K2O (1%), SO4(17%), Mn (31%) 0.06 Wednesday K2O(1%), S (11.8%), Mg (9%),Ultra Magnesium 0.075SO4(11.8%)Ultra Zinc K2O(1%), SO4(8.85%), Zn (20%) 0.009Potassium Chloride K2O (60%) 0.5 FridayMonoammoniumN (12%), P2O5 (61%) 0.42phosphate (MAP)B (0.64%), Cu (1%), Fe (5%),Tradecorp AZ II 0.048Mn (3.5%), Mo (0.3%), Zn (2.4%)C. Biometric and developmental evaluation

[0081] FIG. S23 shows the timeline of the speed breeding protocol in soybean. The plants cultivated under controlled conditions in the greenhouse and under the effect of different photoperiods in the growth chambers were evaluated at the time the seeds were harvested at 60, 67, 74 and 81 days after emergence (DAE) in terms of leaf area (LA, cm2), plant height (PH, cm), main root length (RL, cm), root volume (RV, cm3), aerial part dry mass (APDM, g) and root dry mass (RDM, g).

[0082] To determine LA, high-resolution digital images were taken of all the leaves in each repetition, with a scale (FIG. S6), using a digital camera (Hero 9 Black, GoPro®, USA) and analyzed using ImageJ® software (Rasband 2018). Leaf area was also determined at the time of the physiological evaluations at stages V6 (Pre-flowering), R2 (Full flowering) and R4 (postflowering).

[0083] Plant height (PH, cm) and main root length (RL, cm) were measured using a ruler graduated in millimeters from the base of the stalk to the apex of the aerial part or root. To determine APDM MSPA and RDM, the plant material was dried in a forced air circulation oven (SL - 102, Solab) at 65°C until it reached a constant mass, and then weighed using a semi-analytical balance (ARD110 class II, Ohaus Corporation).

[0084] Root volume (RV) was measured by measuring the displacement of the water column in a graduated cylinder, i.e. by placing the roots, after washing, in a cylinder containing a known volume of water (100 mL). From the difference, the direct answer of the volume of roots was obtained, due to the equivalence of units (1 mL = 1 cm3). The number of pods per plant (NP) and the number of seeds per plant (NS) were also determined by direct counting at harvest time.D. Chlorophyll indices, chlorophyll a fluorescence and gas exchange

[0085] Evaluations of chlorophyll indices, chlorophyll fluorescence and gas exchange were carried out at three times during crop cultivation, at stages V4, R2 and R4 (pre-flowering, full flowering and after flowering, respectively).

[0086] The chlorophyll a and b indices and the chlorophyll a / b ratio were determined using the portable chlorophyll meter ChlorofiLOG1030® (Falker®, RS, Brazil).

[0087] Chlorophyll a fluorescence was determined on the same leaves used for gas exchange analysis, using a FluorPen FP 100 portable fluorometer (Photon Systems Instruments, Drasov, Czech Rep.).

[0088] After the leaves were adapted to the dark for 30 minutes, they were subjected to a pulse of 3000 μmol m−2s−1of blue light (450 nm), measuring the minimum fluorescence (Fo) at 50 ps when all the PSII reaction centers were open and defined as the O step, followed by the J step at 2 ms, the I step at 30 ms and the maximum fluorescence (Fm) when all the PSII reaction centers were closed, known as the P step. The obtained data were used to calculate various bioenergetic indices of photosystem II, such as maximum photochemical quantum yield (Fv / Fm), quantum yield of electron transport (yEo), quantum yield of energy dissipation in the form of heat ($Do), photochemical performance index (PIABS), absorption of energy per reaction center (ABS / RC), and rate of energy dissipation in the form of heat per reaction center (Dio / RC) according to Strasser et al. (2000).

[0089] Gas exchange was determined in the third fully expanded leaf from the apex of the plant, between 08:30 AM and 11:30 AM on a sunny day. The measurements were taken using an infrared gas analyzer (IRGA, LI-6800XT, LI-COR Inc, Lincoln, NE, USA), with photosynthetically active radiation (PAR; 1,000 μmol photons m−2s−1), with 10% blue light and CO₂ concentration (400 μmol mol−1) constant and ambient conditions of temperature (25 ± 1°C), relative humidity (72 ± 0.6%), and vapor pressure deficit (2.6 ± 0.1 kPa). Net photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), intercellular CO₂ concentration (Ci), and instantaneous water use efficiency (WUE = A / E) were evaluated.E. Evaluation of flowering

[0090] The plants were monitored daily to check when the first flower opened and to obtain the number of days from emergence to the start of flowering. After flowering began, the flowers were counted daily, at the same time in the morning, to determine the number of flowers emitted and the duration of the flowering period during the reproductive phase.F. Artificial hybridization

[0091] For artificial hybridization, healthy flower buds from plants cultivated under controlled conditions were used, which would open the next day with the corolla visible through the calyx. All other flowers or buds present on the same node have been removed. The sepals and petals were then removed and the flower buds emasculated, with the pollen grains removed. Next, the newly opened flowers, containing anthers with pollen from the male parent, were gently rubbed onto the stigma of the emasculated (female parent) buds. Crossing was carried out three days after flowering using three parent plants.

[0092] Ten days after artificial hybridization, pods longer than 1 cm were considered in the setting percentage, allowing the efficiency of the process to be calculated. At 30 days after crossing, the total number of seeds in a pod was quantified to determine the average number of seeds per pod produced.G. Harvesting immature seeds and evaluating emergence

[0093] The immature pods were collected in stages (60, 67, 74, and 81 DAE) and dried in a forced-air circulation oven (SL - 102, Solab), at 30°C, for 72 h. After drying, the pods were opened manually and the seeds counted, weighed and then sown in trays with sand. The percentage of seed emergence was determined seven days after sowing, following the rules for seed analysis (RAS) (Brazil 2009). For this evaluation, 4 L of coarse sieved sand and 1 L of vermiculite were mixed homogeneously and placed in polyethylene trays (55 cm x 33 cm x 10 cm) to serve as the substrate. Five longitudinal lines were made on each tray, approximately 1 cm deep, in which the seeds were placed and covered with the same substrate. The trays were wet with a hose to ensure sufficient moisture for germination and seedling emergence, taking care not to uncover the seeds.

[0094] The accumulation of seedling biomass was determined 15 days after sowing, by pulling out all the seedlings, placing them in paper bags, and taking them to a forced air oven (SL - 102, Solab) at 65°C to dry until they reached a constant mass. They were then weighed using a semi-analytical balance (ARD110 class II, Ohaus Corporation).H. Statistical analysis

[0095] The data obtained was previously analyzed for normality (Shapiro-Wilk test) and homoscedasticity (Levene’s test). The data was then submitted to analysis of variance (ANAVA) followed by multiple comparisons using the Tukey test. Subsequently, the multivariate analysis of principal components (PC) was carried out using the " PCA" function and plotted using the “fviz_pca_biplof ’ function of the “factoextra” package (Kassambara & Mundt 2020). Pearson's correlation analysis and the Heatmap were drawn up using the “cor” and “corrplof ’ functions of the “corrplot” package (Wei et al. 2021). The biometric data and the data related to the harvesting of immature seeds were subjected to regression analysis as a function of the evaluation and harvesting seasons, respectively. All the analyses were carried out using the R software version 4.0.2 (R Core Team 2020), considering a probability level of 5%( / ? < 0.05).RESULTSA. Biometric indicators

[0096] The biometric indicators of the different soybean cultivars classified as early (BRS546), semi-early (BRS531) and late (BRS8381) had a significant response (p < 0.05) to the different photoperiods (Table S2). There was a significant effect of the seasons on various indicators, as wellas a significant interaction between the photoperiods and evaluation seasons (Table S2). The plant development throughout the study (FIG. S10 and FIG. S 11) and during the harvest and evaluation seasons at different seasons can be observed in FIGs. S12, S13, S14 and S 15.

[0097] Plant height (PH), aerial part dry mass (APDM), number of pods (NP), and number of seeds (NS) as a function of the different photoperiods and measurement seasons for the different soybean cultivars are shown in FIG. 1, where plant height (PH), aerial part dry mass (APDM), number of pods (NP), and number of seeds (NS) of soybean plants of different cultivars and development cycles as a function of different photoperiods and measurement. Bars represent average ± SE (n = 4). Averages followed by the same uppercase letter between photoperiods and lowercase letters within each photoperiod do not differ according to Tukey's test (p < 0.05).

[0098] The PH for the early (FIG. la) and late (FIG. 1c) soybean cultivars was higher under the 12 h photoperiod, ranging from 103 to 143 cm for the early cultivar and from 94 to 129 cm for the late cultivar, depending on the evaluation seasons. As for the semi-early cultivar, the highest heights were observed for the treatment in full sun from 74 DAE (~91 cm) and under the 10 h photoperiod at 67 DAE (85.3 cm) and the 12 h photoperiod at 60 DAE (90.0 cm) (FIG. lb).

[0099] For the 10 h photoperiod, there was no difference between the seasons evaluated, regardless of the soybean cultivar used, with an average of 83.6, 83.6, and 84.8 cm for the early, semi-early, and late cultivars, respectively (FIGs. la, lb and 1c). For the other photoperiods, there was a variation in the plants’ response depending on the evaluation seasons. In the early and late cultivars, the highest PHs were observed at 60 DAE and 74 DAE, respectively (FIGs. la and 1c). For the semi-early cultivar, there was variation depending on the measurement seasons and photoperiods used (FIG. lb).

[0100] Plant growth and development are regulated by many internal and external signals, such as temperature (Purcell et al. 2013, Bhatta et al. 2021), light quality and intensity, and particularly photoperiod (Bhatta et al. 2021). In a pioneering study, Garner & Allard (1930) found that photoperiod affected the vegetative development of soybean plants in different locations, significantly affecting plant height. Herein, it was observed that soybean plants under a longer photoperiod had higher plant heights when compared to those under a shorter photoperiod, corroborating the results obtained in this study. Camara et al. (1997) also observed that increases in photoperiod promote an increase in the height of soybean plants. Plant height was 42 to 103% (between 10 and 40 cm) higher when compared to those under a shorter photoperiod. They also found that the higher plant height resulted from plant elongation and an increase in the number of nodes, which was increased by 33 to 57%. Therefore, longer photoperiods help to produce larger plants, mainly due to the increase in the plants’ photosynthetic capacity, which leads to highergrowth (Camara etal. 1997). Similarly, the opposite has also been observed, and the results confirmed that shorter photoperiods result in smaller plants when compared to plants under longer photoperiods (Watson et al. 2018, Jahne et al. 2020, and Harrison et al. 2021). According to Bhatta et al. (2021), the lower plant height may be due to the reduction in the vegetative cycle of soybean plants due to the reduction in photoperiod. As it is a short-day plant, the shorter photoperiod anticipates reproductive development and flowering (Setiyono et al. 2007).

[0101] The MSPA produced by the soybean plants was higher in plants grown in full sun, regardless of the cultivar used (Table S8), except for the late cultivar, and the MSPA produced under a 12 h photoperiod was similar to full sun (Table S8). The response of soybean plants to APDM production as a function of the measurement season and photoperiods is shown in FIGs. Id, le, and If.

[0102] For the early cultivar, the dry mass production data is best explained by the quadratic model for all photoperiods (FIG. Id). Maximum APDM production was reached at 63.3, 64.3, 67.8, and 70.5 DAE when it reached 5.32, 6.18, 16.1, and 23.4 g respectively for the 08, 10, 12 h and full sun photoperiods (FIG. Id). The semi-early cultivar was only influenced by photoperiods and the highest APDM production (27.2 g) was obtained under full sun conditions (FIG. le).

[0103] The results for the late cultivar were better fitted to the linear model for the 08 and 12 h photoperiod, and quadratic for the 10 h photoperiod, while in full sun there was no fit to the models evaluated (FIG. If). A linear reduction in APDM was observed at the 08 h photoperiod, with the highest production (3.58 g) at 60 DAE. Under the 10 h photoperiod, the maximum production (11.0 g) was estimated at 68.3 DAE, while under the 12 h photoperiod, the highest production (23.2 g) was obtained at 81 DAE. In full sun, the average dry mass production was 21.1 g (FIG. If).

[0104] The reduction in dry mass over time, especially in the longer photoperiods for the early cultivar, is due to possible plant senescence and leaf fall. The linear response observed for the late cultivar, during the same photoperiods, may have been due to the fact that the plants were still developing.

[0105] Photoperiod regulates plant growth and development (Bhatta etal. 2021), mainly by increasing photosynthetic capacity (Gajdosik et al. 2022), resulting in greater growth (Garner & Allard 1930, Camara et al. 1997), as observed in this study. Consequently, the production of APDM behaves in a similar way, since greater vegetative development results in a higher contribution of plant biomass (Gajdosik et al. 2022). Feng et al. (2019) also reported that reduced light conditions reduce the dry matter production of soybean plants. Corroborating the results obtained in this study, Harrison et al. (2021) found that shorter photoperiods result in plants with less accumulation of vegetative biomass. Shorter photoperiod anticipates the reproductive development of soybeans, i.e.anticipates flowering (Setiyono etal. 2007). As a consequence of this early flowering, there is a reduction in plant biomass production (Bhatta et al. 2021), as can be seen for the 08 h photoperiod for the early (FIG. 1c), semi-early (FIG. Id) and late (FIG. le) soybean cultivars.

[0106] The number of pods (FIGs. 1g, Ih, and li) and seeds (FIGs. Ij, Ik, and 11) had similar responses to the evaluation seasons. The highest number of pods and seeds was observed for the longer photoperiods for the early and semi-early cultivars, while for the late cultivar, the lowest values were observed under an 8 h photoperiod, with no significant differences among the others (Table S8).

[0107] For the early soybean cultivar, there was a quadratic model fit for the number of pods (FIG.1g) and seeds (FIG. Ij) regardless of the photoperiod, except for the number of pods for the 10 h photoperiod, which did not fit the models evaluated (FIG. 1g). Under the 08 h photoperiod, the inverse quadratic model was fitted, with the highest values for pods (31.9) and seeds (57.9) observed at 60 DAE. For the 10 h photoperiod, the average number of pods was 28.7, while the maximum number of seeds was 73.1, estimated at 70.9 DAE. For the longer photoperiods (12 h and full sun) the maximum number of pods (62.8 and 62.0) was observed at 70 and 73.9 DAE respectively. The maximum number of seeds was observed at 68.2 and 73.5 DAE, with 135.9 and 129.1 seeds, respectively (FIG. Ij).

[0108] The data obtained for the semi-early cultivar was best explained by the quadratic model for the evaluation seasons under the effect of the longer photoperiods, except for the number of seeds in full sun, which fitted the linear model (FIGs. Ih and Ik). For the 08 h photoperiod, there was no fit to the models, and the plants reached an average of 27.5 pods and 49.2 seeds. In the 10 and 12 h photoperiods, the maximum number of pods and seeds were obtained at 69 and 72 DAE, respectively. The maximum number of pods and seeds estimated for these periods was 36.6 and 53.1 pods and 89.3 and 101.7 seeds for the 10 and 12 h photoperiods, respectively. In full sun conditions, the maximum number of pods (51.4) and seeds (95.6) was estimated at 81 DAE.

[0109] For the late cultivar, there was a quadratic fit for the data on number of pods and seeds, except for the 12 h photoperiod, which was better explained by the linear model (FIGs. li and 11). In addition, the number of seeds under the 08 h photoperiod did not fit the models evaluated, with an average of 49.7 seeds. As for the number of pods under the 08 h photoperiod, there was a quadratic fit with the highest number of pods (27.1) at 72.9 DAE. For the 10 h photoperiod, the highest number of seeds (92.4) and pods (43.0) was obtained at 76.8 and 78.6 DAE respectively. Under a 12 h photoperiod, the highest values for pods (58.2) and seeds (121.8) were obtained at 81 DAE, while in full sun, the highest values for pods (56.6) and seeds (128.4) were observed at approximately 72 DAE. Harrison et al. (2021) also verified the effect of photoperiod on the numberof pods and seeds per plant. However, the authors observed maximum values of 16.8 pods and 30.9 seeds with 12 h, which are lower than those obtained in the present study. This difference may be due to the climatic conditions in each region, as well as the different soybean genotypes evaluated.

[0110] The results for the biometric indicators leaf area (LA), root length (RL), root dry mass (RSM) and root volume (RV) are shown in FIG. S7. In general, the leaf area (LA) of soybean plants was higher when cultivated in full sun, regardless of the cultivar evaluated (Table S8). The LA data for the early (FIG. S7a) and semi-early (FIG. S7b) cultivars were best explained by the decreasing linear model as a function of the evaluation seasons, except for the early cultivar when in full sun, which fitted the quadratic model. The highest LA values were at 60 DAE for the linear adjustments. The early cultivar reached LA values of 775.7, 903.9, and 1650.5 cm2, while for the semi-early cultivar, it was 794.4, 1142.7, and 1879.8 cm2for the 08, 10, and 12 h photoperiod, respectively. In full sun, the early cultivar reached an LA of 1944.8 cm2at 69.8 DAE, and the semi-early cultivar an average AF of 2047.9 cm2.

[0111] The AF data for the late cultivar fitted the decreasing linear model for the 08 h photoperiod and quadratic for the 10 h photoperiod and in full sun, while for the 12 h photoperiod there was no fit to the models, with an average AF of 2474.2 cm2(FIG. S7c). Under the 08 h photoperiod, the highest LA was 667.9 cm2at 60 DAE, while under the 10 h photoperiod and in full sun, the highest LA was observed at 68 DAE, with 1155.8 and 2754.2 cm2, respectively.

[0112] Leaves are the receptors of photoperiod signals that promote the regulation of flowering in soybeans (Setiyono etal. 2007). Low light conditions promote upward growth of stems and petioles, reducing the leaf area of the plant (Feng et al. 2019), as also observed in the present study. Generally, plants modulate their leaf anatomy and physiology in response to irradiance, developing thicker leaves with a higher ratio of mesophyll to surface area (Fritschi & Ray 2007), possibly with a view to greater photosynthetic efficiency. In addition, the lower LA observed in the 08 h photoperiod is due to the early flowering of the plants leading to a reduction in total biomass (Bhatta etal. 2021).

[0113] The RL of the soybean plants of the early cultivar (FIG. S7d) at 60 DAE was higher in the 10 h photoperiod (45.1 cm), while at 67 DAE there was no difference between the photoperiods evaluated, with an average RL of 41.4 cm. In the 12 h photoperiod and full sun, the highest root length was observed at 74 DAE (-46.5 cm) and 81 DAE (-40 cm), when compared to the 08 h photoperiod. For the semi-early (FIG. S7e) and late (FIG. S7f) cultivars, there was no difference between the photoperiods at 60 DAE, which had an average RL of 39.4 and 36.1 cm, respectively. At 67 and 74 DAE, the highest RL of the semi-early soybean plants was observed in the full sun photoperiod (52.5 and 57.5 cm respectively), while the late cultivar had the highest RL in the 10 hphotoperiod at 67 and 81 DAE (42.5 and 45 cm respectively) and with 12 h at 67 DAE (44.3 cm). For the late cultivar, there was no difference in RL between the photoperiods at 74 DAE (~ 37.3 cm).

[0114] RDM was higher in the longer photoperiods (12 h and full sun) regardless of the soybean cultivar used. For the early (FIG. S7g) and semi-early (FIG. S7h) cultivars, the highest root dry mass was produced in plants under full sun (-4.72 and 5.48 g, respectively), except at 67 DAE for the early cultivar which was the same as that obtained with a 12 h photoperiod (-3.74 g). The lowest RDM values were observed in the 08 and 10 h photoperiod, regardless of the soybean cultivar evaluated. The DMR of the early cultivar (FIG. S7g) and semi-early (FIG. S7h) at 60 DAE, the semi-early cultivar at 67 DAE and 81 DAE and the late cultivar at 74 DAE was in the following order: full sun > 12 h photoperiod > 10 h photoperiod = 08 h photoperiod. The early and semi-early cultivars at 74 DAE and the late cultivar (FIG. S7i) at 67 DAE followed the order: full sun > 12 h photoperiod > 10 h photoperiod > 08 h photoperiod. With the exception of the late cultivar at 81 DAE, there was a tendency for the RDM of the soybean plants to decrease as the amount of daily light decreased. A reduction in root dry matter production is expected in soybean plants under reduced light conditions (Feng et al. 2019).

[0115] RV behaved similarly to root dry mass, decreasing as a result of the reduction in photoperiod. For the early (FIG. S7j) and late (FIG. S71) cultivars, the largest root volumes were observed in full sun and 12 h photoperiod, while for the semi-early cultivar (FIG. S7k) the largest root volumes were obtained only in full sun. Root volume behaved as follows: full sun > 12 h photoperiod > 10 h photoperiod > 08 h photoperiod for all the soybean cultivars evaluated. The lower production of root dry mass under reduced light conditions, as observed by Feng et al.(2019), may be related to the lower volume of roots produced by the plants under these conditions, as observed in the present study, in addition to the shorter root length.5.2. Chlorophyll indices, chlorophyll a fluorescence and gas exchange

[0116] The chlorophyll a, chlorophyll Z>, chlorophyll a I b ratio, and total chlorophyll indices were influenced by the different photoperiods and measurement seasons (Table S3), whose results are shown in Table S9. The chlorophyll a index was lower in full sun, regardless of the soybean cultivar evaluated, as were the chlorophyll b index and total chlorophyll. The chlorophyll alb ratio was higher in full sun when compared to the other photoperiods. The higher chlorophyll a, Z>, and total indices obtained inside the growth chamber were possibly due to the lower light intensity, so the plants invest more in chlorophyll to compensate for this luminosity (Wang et al. 2021, Tang et al. 2022). As for the measurement seasons, there was an increase in chlorophyll a and b levels, and consequently in total chlorophyll levels as the soybean development cycle progressed, with thevalues observed in pre-flowering being lower than those observed in post-flowering, regardless of the soybean cultivar evaluated.

[0117] The increase in chlorophyll in relation to time (stages of development) was possibly due to the greater need for energy to meet drains (pod formation, flowers, etc.) (Camara 2009). The chlorophyll alb ratio had the opposite result, with the highest ratios observed in pre-flowering, and the lowest values in post-flowering. The most significant differences between the photoperiods were observed during pre-flowering and full flowering, while in post-flowering, there were fewer or no differences between them.

[0118] A longer photoperiod favors photosynthesis, since the quality and quantity of light affect the excitation of photosystems I and II, key components of photosynthetic processes (Gajdosik et al.2022). According to Gajdosik et al. (2022), plants grown under long days have chloroplasts with smaller grana stacks and a higher chlorophyll content, demonstrating that photosynthetic capacity is increased. However, this behavior was only observed for the semi-early cultivar, which had a higher chlorophyll content during the longer photoperiod, while there was no difference between the photoperiods for the early and late cultivars. According to Fritschi & Ray (2007), an increase in light radiation causes a reduction in total chlorophyll content and an increase in the chlorophyll a and b ratio. In this study, the same amount of radiation was used for all the artificial photoperiods, which explains the results obtained. Crop growth and dry matter production are largely dependent on photosynthesis, so the stress of lower photoperiod directly affects crop development (Feng et al.2019), confirming the results presented in FIG. 1 and FIG. S7.

[0119] The indicators related to chlorophyll a fluorescence were not influenced by the photoperiods evaluated, except for the energy dissipation flow in the form of heat per reaction center (Dio / RC) for the semi-early cultivar (Table S4). The evaluation seasons influenced all the indicators evaluated, regardless of the soybean cultivar. For the early cultivar, there was a significant interaction for the maximum emitted fluorescence (Fm), while for the semi-early and late cultivars, the interaction between the sources of variation was significant, except for the maximum emitted fluorescence (Fm) for the semi-early cultivar.

[0120] The photoperiods in isolation had no significant effect on the indicators related to chlorophyll a fluorescence (Table S10, S 11, and S12), as observed previously for most of the indicators related to gas exchange. For the early cultivar (Table S10) the highest emitted fluorescence (Fm) was observed in full sun after flowering (506.8) when compared to the 10 h photoperiod (447.7).

[0121] For the semi-early cultivar (Table S10), the effect of photoperiod on the indicators was observed in pre-flowering. It was observed that the maximum quantum yield of photosystem II(Fv / Fm) and the quantum yield of electron transport (yEo) were higher in full sun, while the initial fluorescence (Fo), quantum yield of energy dissipation in the form of heat ($Do) and the flow of energy dissipation in the form of heat per reaction center (Dio / RC) were higher in the 12 h photoperiod.

[0122] The semi-early and late cultivars were significantly influenced by photoperiod on chlorophyll a fluorescence indicators in pre-flowering as well as in full flowering. For the effect of the evaluation season, it was found that initial fluorescence (Fo), maximum fluorescence (Fm), the quantum yield of energy dissipation in the form of heat ($Do), the energy absorption index per reaction center (ABS / RC) and the flow of energy dissipation in the form of heat per reaction center (Dio / RC) were higher in pre-flowering.

[0123] The effective quantum yield of photochemical energy conversion (Fv / Fo), maximum quantum yield of photosystem II (Fv / Fm), quantum yield of electron transport (yEo), and photochemical performance index (PIABS) were higher in full or post-flowering. The Fv / Fm observed in full and post-flowering for the early and semi-early cultivars (Table S10 and S 11) and in post-flowering for the late cultivar (Table S12) may be indicative of higher efficiency in the use of radiation by photochemistry and, consequently, greater efficiency in carbon assimilation (Tester & Bacic 2005).

[0124] The higher efficiency of radiation use may be related to the higher chlorophyll levels observed. It can be seen that the different photoperiods did not affect the plant's photosynthetic apparatus, since the Fv / Fm values were higher than 0.75 (Santos et al. 2010), so there was no reduction in the plant's photosynthetic potential (Silva et al. 2015). The Fv / Fo results can also be used as an indicator of the maximum efficiency in the photochemical process in the PSII and / or the potential photosynthetic activity (maximum ratio of quantum production of the competing photochemical and non-photochemical processes in the PSII) (Silva et al. 2015). Therefore, it can be seen that the different photoperiods can be used in speed breeding processes without negatively compromising the physiology of soybean plants.

[0125] In addition, the differences observed for the evaluation seasons are due to the different ages of the leaves and plants. Bielczynski et al. (2017) found that chlorophyll a fluorescence results vary with both leaf age and plant age. They found an increase in the quantum yield of photochemical conversion in photosystem II and a reduction in the dissipation of energy in the form of heat as the plants developed and grew older. These results confirm those obtained in this study.

[0126] The fact that the Fv / Fmincreased in relation to the advance in the developmental stage possibly indicates consolidation of photosystem II. The increase in the chlorophyll index was due to the demand for photoassimilates for the production of flowers, pods and grains (Camara 2009), andconsequently resulted in the stability of the photochemical efficiency indices, with Fv / Fmequal to or higher than 0.75 indicating the absence of photoinhibition (Santos et al. 2010). In addition, the reduction in the ratio between chlorophyll a and b reinforces the stability or consolidation of photosystem II, which is rich in chlorophyll b. This ensured less heat dissipation, maintenance of high rubisco levels, and carbon assimilation rates.

[0127] The physiological indicators related to photochemical processes and gas exchange of the different soybean cultivars classified as early (BRS546), semi-early (BRS531) and late (BRS8381) had a significant response (p < 0.05) to the different evaluation seasons (Table S3), except for the net photosynthetic rate (A) for the early cultivar. As for the effect of the photoperiods evaluated, significance was observed for stomatal conductance (gs) in the early cultivar, and forintercellularCO₂ concentration (Ci) in the late cultivar. For the semi-early cultivar, only the intercellular CO2 concentration (Ci) was not significantly influenced by the photoperiods. There was a significant interaction between photoperiods and evaluation seasons for the indicators measured, except for instantaneous water use efficiency (WUE) for the early cultivar (Table S3).

[0128] In the early cultivar, the net photosynthetic rate (A), transpiration rate (E), intercellular CO2 concentration (Ci) and instantaneous water use efficiency (WUE) were not significantly influenced by the different photoperiods and did not differ from each other (Table 4).Table 4. Physiological indicators (average ± standard error) related to the gas exchange of different soybean cultivars under the effect of different photoperiods at different measurement seasons.Early = BRS546 (GM 6.0)- A (μmol m⁻² s⁻¹) - Season³ Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 20.9±0.95 aA 21.8iO.99 aA 22.5±0.53 aAB 21.7i0.48 Photoperiod 10 h 20.5il.l7 abA 23.lil.14 aA 19.4±0.71 bB 21.0i0.72 Photoperiod 12 h 21.5il.08 aA 22.7±0.99 aA 19.9±0.85 aAB 21.4i0.61 Full sun 22.6±0.65 aA 17.9il.25 bB 23.0±0.67 aA 21.2i0.85 Average 21.4i0.49 21.4i0.72 21.2i0.51- Ci (μmol mol⁻¹) - Photoperiod 08 h 316.9±1.91 aA 306.0il.75 bB 308.6±2.58 abA 310.5il.79 Photoperiod 10 h 319.1±3.19 aA 303.4±4.85 bB 312.7±2.30 abA 311.8±2.70 Photoperiod 12 h 324.0±2.72 aA 307.9il.35 bB 293.7±0.67 cB 308.6±3.84 Full sun 318.li3.80 aA 320.6±3.39 aA 293.7il.65 bB 310.8±3.99 Average 319.5il.50 a 309.5±2.21 b 302.2±2.38 c - WUE (μmol mmol⁻¹) - Photoperiod 08 h 1.97i0.11 4.96±0.52 3.77±0.25 3.57±0.41 Photoperiod 10 h 1.73i0.09 4.75±0.43 3.53±0.28 3.34± 0.41 Photoperiod 12 h 1.67i0.07 4.60±0.28 4.06±0.29 3.45±0.40 Full sun 1.70i0.07 4.18±0.52 4.49±0.10 3.46±0.41 Average 1.77±0.05 c 4.63±0.21 a 3.97±0.14 b Early = BRS546 (GM 6.0) - E (mmol m⁻² s⁻¹) - Season Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 10.7±0.35 aC 4.56±0.56 cA 6.04±0.43 bA 7.08±0.82 Photoperiod 10 h 11.9iO.72 aBC 4.92±0.23 bA 5.54±0.24 bA 7.44±0.97 Photoperiod 12 h 12.9±0.26 aAB 4.94±0.15 bA 4.94±0.39 bA 7.59il.l4 Full sun 13.3±0.23 aA 4.36±0.34 bA 5.14±0.24 bA 7.62il.23 Average 12.18±0.33 a 4.70±0.17 c 5.41i0.19 b ■gs (mol m2s ’)■ Photoperiod 08 h 0.81±0.04 aB 0.71±0.04 aA 0.74±0.03 aA 0.75±0.02 AB Photoperiod 10 h 0.83±0.01 aB 0.69±0.02 bA 0.63±0.02 bAB 0.72±0.03 B Photoperiod 12 h 1.17i0.05 aA 0.72±0.03 bA 0.51±0.05 cB 0.80±0.09 A Full sun 1.23i0.04 aA 0.55±0.04 bB 0.56±0.02 bB 0.78±0.10 AB Average 1.01i0.05 a 0.67±0.02 b 0.61±0.03 b - LA (cm2) - Photoperiod 08 h 150.7il3.8 470.1±61.9 aB 743.7±108 aB 454.9±82.2 C bBC Photoperiod 10 h 253.3±27.0 bB 944.9±105 aA 839.5±88.5 aB 679.5±101 B Photoperiod 12 h 515.6±47.2 cA 1013.4±159 bA 1666.8±56.6 aA 1065.3±152 A Full sun 123.2±10.0 cC 962.9±73.6 bA 1552.4±112 aA 879.5±181 A Average 260.7±42.0 c 847.8±74.2 b 1200.6±114 a Semi-early = BRS531 (GM 7.3) - A (μmol m⁻² s⁻¹) - Season | Treatment | Pre-flowering | Full flowering | Post-flowering | Average | Photoperiod 08 h 22.1±0.72 aA 21.1iO.14 abA 20.1±0.57 bAB 21.liO.37A Photoperiod 10 h 18.2±0.55 bB 22.5±0.74 aA 19.4±0.48 bAB 20.0±0.63 AB Photoperiod 12 h 22.1±0.26 aA 20.7±0.58 aA 18.7±0.18 bB 20.5±0.46 AB Full sun 21.5iO.41 aA 16.1±0.55 bB 21.2iO.16 aA 19.6±0.77 B Average 21.0i0.48 a 20.1i0.66 b 19.9i0.29 b - Ci (μmol mol⁻¹) - Photoperiod 08 h 323.9i3.03 aA 305.3i3.17 bB 317.6i0.66 abA 315.6i2.69Photoperiod 10 h 322.0il.95 aA 301.1±1.50 bB 314.5i4.19 abA 312.5i3.55Photoperiod 12 h 321.2±2.19 aA 301.3±6.37 bB 304.6±7.94 bAB 310.5±4.10 Full sun 313.7±4.87 aA 326.7±5.02 aA 291.2±4.81 bB 309.0±5.11 Average 320.2±1.76 a 308.6±3.66 b 307.0±3.51 b - WUE (μmol mmol⁻¹) - Photoperiod 08 h 1.68±0.07 cAB 4.32±0.21aAB 3.28±0.17 bB 3.10±0.34 B Photoperiod 10 h 1.64±0.07 cB 4.92±0.18 aA 3.31±0.20 bB 3.29±0.41 AB Photoperiod 12 h 1.70±0.07 cAB 4.89±0.08 aA 3.83±0.22 bAB 3.48±0.41 A Full sun 2.11±0.10 cA 3.50±0.04 bB 4.38±0.14 aA 3.33±0.29 AB Average 1.78±0.06 c 4.41±0.16 a 3.70±0.14 b Semi-early = BRS531 (GM 7.3) E (mmol in2s ') - Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 13.1±0.30 aA 4.92±0.24 bA 6.19±0.43 bA 8.08±1.10 A Photoperiod 10 h 11.1±0.46 aAB 4.58±0.18 cA 5.91±0.30 bA 7.22±0.87 B Photoperiod 12 h 13.1±0.56 aA 4.23±0.06 bA 4.94±0.32 bA 7.40±1.22 AB Full sun 10.3±0.52 aB 4.62±0.16 bA 4.85±0.13 bA 6.57±0.80 B Average 11.9±0.38 a 4.59±0.10 c 5.47±0.21 b - gs(mol m⁻² s⁻¹) - Photoperiod 08 h 1.24±0.04 aA 0.68±0.04 bA 0.75±0.03 bA 0.89±0.08 A Photoperiod 10 h 0.88±0.06 aB 0.65±0.06 bA 0.72±0.02 abA 0.75±0.04 B Photoperiod 12 h 1.16±0.10 aA 0.57±0.04 bA 0.51±0.05 bB 0.74±0.10 B Full sun 0.82±0.06 aB 0.52±0.06 bA 0.47±0.05 bB 0.60±0.06 B Average 1.03±0.06 a 0.60±0.03 b 0.61±0.04 b - LA (cm2) - Photoperiod 08 h 286.6±13.6 bB 896.8±84.1 aB 756.3±68.8 aC 646.6±85.3 C Photoperiod 10 h 431.4±22.2 bA 1545.8±139 aA 1222.9±123 aB 1066.7±152 B Photoperiod 12 h 441.8±44.3 bA 1503.9±123 aA 1322.7±93.7 aB 1089.5±148 B Full sun 189.5±21.9 cB 1236.5±102 bAB 2547.6±116 aA 1324.5±295 A Average 337.3±29.9 c 1295.7±84.2 a 1462.4±177 a Late = BRS8381 (GM 8.3) - A (μmol m⁻² s⁻¹) - Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 19.8±1.75 bA 24.3±0.59 aA 21.3±0.32 abA 21.8±0.80 Photoperiod 10 h 22.7±0.38 aA 22.2±1.47 aAB 20.4±0.42 aA 21.7±0.56 Photoperiod 12 h 20.8±0.32 abA 21.4±0.44 aAB 18.0±1.45 bA 20.1±0.65 Full sun 21.3±0.88 aA 19.1±0.46 aB 20.3±1.39 aA 20.2±0.58 Average 21.1±0.52 ab 21.7±0.61 a 20.0±0.56 b - Ci (μmol mol⁻¹) - Photoperiod 08 h 324.2±3.79 aA 290.9±3.65 bC 318.4±2.56 aA 311.8±4.71 A Photoperiod 10 h 320.7±1.36 aA 295.0±6.53 bBC 316.8±4.04 aAB 310.8±4.15 A Photoperiod 12 h 321.8±4.40 aA 316.6±1.04 aA 303.6±3.01 bB 314.0±2.82 A Full sun 321.1±2.60 aA 308.7±4.54 aAB 245.6±4.10 bC 291.8±10.2 B Average 321.9±1.50 a 302.8±3.32 b 296.1±7.83 c - WUE (μmol mmol⁻¹) - Photoperiod 08 h 1.68±0.11 cA 5.24±0.16 aA 3.41±0.24 bC 3.44±0.45 Photoperiod 10 h 1.83±0.05 cA 4.89±0.17 aAB 3.46±0.26 bC 3.39±0.39 Photoperiod 12 h 1.81±0.13 bA 4.24±0.18 aB 4.16±0.14 aB 3.40±0.35 Full sun 1.71±0.08 cA 4.06±0.21 bB 5.26±0.43 aA 3.68±0.47Average 1.76±0.05 c 4.61±0.15 a 4.08±0.23 bLate = BRS8381 (GM 8.3)E (mmol m⁻² s⁻¹) Season Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 11.8±0.81 aA 4.65±0.25 cA 6.36±0.50 bA 7.60±0.96 Photoperiod 10 h 12.4±0.43 aA 4.56±0.38 bA 5.97±0.43 bAB 7.66±1.06 Photoperiod 12 h 11.6±0.59 aA 5.06±0.12 bA 4.36±0.46 bBC 7.03±1.02 Full sun 12.4±0.26 aA 4.75±0.30 bA 4.00±0.62 bC 7.06±1.17 Average 12.1±0.27 a 4.75±0.13 b 5.17±0.35 b - gs(mol m⁻² s⁻¹) - Photoperiod 08 h 0.85±0.01 aB 0.61±0.05 aA 0.85±0.06 aA 0.77±0.04 Photoperiod 10 h 1.16±0.06 aA 0.60±0.11 bA 0.76±0.06 bA 0.84±0.08 Photoperiod 12 h 1.04±0.09 aAB 0.79±0.02 bA 0.43±0.11 cB 0.76±0.09 Full sun 1.05±0.05 aAB 0.65±0.05 bA 0.34±0.07 cB 0.68±0.09 Average 1.03±0.04 a 0.66±0.04 b 0.59±0.07 b - LA (cm2) - Photoperiod 08 h 270.8±62.3 bBC 880.3±99.7 aB 682.2±95.2 aB 611.1±89.1 D Photoperiod 10 h 369.4±22.6 cAB 1422.8±136 aA 953.4±145 bB 915.2±143 C Photoperiod 12 h 525.9±29.2 cA 1464.8±142 bA 2518.9±129 aA 1503.2±252 A Full sun 120.2±19.7 cC 1098.0±88.8 aB 2235.2±105 aA 1151.1±264 BAverage 321.6±41.6 c 1216.5±81.8 b 1597.4±211 a3Pre-flowering (Stage V6), full flowering (Stage R2), and post-flowering (Stage R4), respectively. A: Net photosynthetic rate; E: transpiration rate; gs: stomatal conductance; Ci: intercellular CO2 concentration; WUE: instantaneous water use efficiency; LA: leaf area. Averages followed by the same uppercase letter between photoperiods and lowercase letters within each photoperiod do not differ according to Tukey's test ( / ? < 0.05).

[0129] Stomatal conductance (gs) was higher in the 12 h photoperiod compared to the 10 h photoperiod, but did not differ from the other photoperiods. Transpiration rate (E), intercellular CO2 concentration (Ci) and stomatal conductance (gs) were higher in pre-flowering soybean plants, while instantaneous water use efficiency (WUE) was higher in full flowering.

[0130] Net photosynthetic rate (A), intercellular CO2 concentration (Ci) and instantaneous water use efficiency (WUE) did not differ in pre-flowering, while transpiration rate (E) and stomatal conductance (gs) were higher in full sun and in the 12 h photoperiod when compared to the 08 h photoperiod. In full flowering, the full sun treatment was similar to or lower than the results obtained by the other photoperiods, except for the intercellular CO2 concentration (Ci), which was higher in full sun. In post-flowering there was little or no difference between the photoperiods, except for the intercellular CO2 concentration (Ci) which was lower in full sun and in the 12 h photoperiod.

[0131] The semi-early cultivar (BRS531) (Table 4) had a higher net photosynthetic rate (A), transpiration rate (E) and stomatal conductance (gs) under the 08 h photoperiod when compared to full sun, while for intercellular CO2 concentration (Ci) and instantaneous water use efficiency (WUE) there was little or no difference between the photoperiods. Measurement at pre-flowering resulted in higher values for the gas exchange indicators, except for instantaneous water use efficiency (WUE), which was higher when measured at full flowering.

[0132] For the late cultivar (Table 4) there was no difference between the photoperiods for net photosynthetic rate (A), transpiration rate (E), and instantaneous water use efficiency (WUE). Stomatal conductance (gs) was higher in the 10 h photoperiod when compared to full sun and intercellular CO2 concentration (Ci) was lower in full sun. As for the measurement seasons, the lowest results for transpiration rate (E) and stomatai conductance (gs) were observed at full flowering and post-flowering. The net photosynthetic rate (A) was higher at full flowering compared to post-flowering, as was the instantaneous water use efficiency (WUE). The intercellular CO2 concentration (Ci) decreased as the soybean cycle progressed, being highest in pre-flowering, similar to what happened with the other cultivars.

[0133] According to Feng et al. (2019) photosynthetic rate (A), transpiration (E) and stomatal conductance (gs) decrease in low light conditions, limiting plant development and biomass accumulation, since net photosynthetic rate (A) is the main driver of the plant's carbon balance. However, in this study, there was no reduction in net photosynthetic rate (A) with the reduction in photoperiod. This may have been due to the fact that the amount of light used in the study was sufficient, even though it was used for a short period of time when compared to the 12 h photoperiod. This can be confirmed by the results of Feng et al. (2019) who found that increasingthe light intensity in growth chamber studies led to an increase in the net photosynthetic rate (A), stomatal conductance (gs), intercellular carbon dioxide levels (Ci) and transpiration rate (E) of soybean plants. Li et al. (2020) also found changes in stomatal conductance (gs), intercellular carbon dioxide levels (Ci), and transpiration rate (E) in soybean plants as a function of different light conditions. According to the authors, the changes are probably due to non-stomatal limitations, such as photoinhibition of photosystem II.

[0134] The chlorophyll content in leaves is often used to estimate the photosynthetic potential of plants, due to its direct link with the absorption and transfer of light energy (Rego & Possamai 2004), as well as generally having a positive correlation with the photosynthetic rate (A) (Lee et al.2007). However, this relationship does not always exist, as the other components of the photochemical stage, as well as the biochemical stage of photosynthesis, can limit the process (Chappelle & Kim 1992) and in some circumstances, plants with fewer pigments are able to use them more efficiently (Lee et al. 2007). This can be seen in the plants under the influence of the 08 h photoperiod, which generally had the smallest leaf area (Table 4 and Fig. S7a, S7b and S7c). Even so, no significant changes were observed in gas exchange, chlorophyll a fluorescence and chlorophyll indices, showing that these plants had high photosynthetic and physiological efficiency.5,3, Flowering

[0135] The different photoperiods influenced the duration of the vegetative phase and the reproductive phase (flowering) of the soybean cultivars evaluated (FIG. 2 and Table S5). FIG. 2 shows the duration of the vegetative period and flowering period during the reproductive phase of different soybean cultivars under the effect of different photoperiods. Note: Green bar represents the duration of the vegetative phase until the start of flowering; the color change in the bar from green to brown represents the start of flowering; brown bar represents the duration of the flowering period. In general, the 08 h photoperiod provided the shortest duration of the vegetative phase, taking 27.6 and 28.4 days after planting (DAP) for flowering to begin, for the early and late cultivars, while for the semi-early cultivar, it occurred under the 08 and 10 h photoperiod at 29.6 DAP.

[0136] The start of the early cultivar flowering was brought forward by 1.6, 4.6 and 10.4 days when under the influence of the 08 h photoperiod, compared to the 10 h, 12 h and full sun photoperiods, respectively. The semi-early cultivar started flowering 2 days later (29.6 DAP) than the early cultivar with the 10 h photoperiod. The use of the 10 h photoperiod shortened the vegetative phase by 0.4, 3.4 and 11.4 days when compared to the 08 h, 12 h and full sun photoperiods, respectively. The late cultivar started flowering at 28.4 DAP using the 08 hphotoperiod. For this cultivar, the vegetative phase was shortened by 3.6, 16 and 16 days for the 10 h, 12 h and full sun photoperiods, respectively, when compared to the 08 h photoperiod.

[0137] The speed breeding technique used accelerates flowering by providing a shorter night period for long-day and neutral-day plants (Watson et al. 2018, Gosh et al. 2018) and a longer night period for short-day plants (Jahne et al. 2020, Bhatta et al. 2021) such as soybeans. Therefore, as a short-day crop, soybeans are very sensitive to photoperiod, and in very long days flowering is negatively influenced, with the longer the photoperiod, the longer it takes for the plant to start flowering (Garner & Allard 1930, Purcell et al. 2013, Jahne et al. 2020).

[0138] However, other plants can also be used in the speed breeding embodiments described herein, such as alfalfa, apple, apricot, artichoke, asparagus, avocado, banana, barley, beans, beet, blackberry, blueberry, Brassica, broccoli, brussel sprouts, cabbage, canola, carrot, cassava, cauliflower, a cereal, celery, cherry, citrus, Clementine, coffee, com, cotton, cucumber, eggplant, endive, eucalyptus, figs, grape, grapefruit, groundnuts, ground cherry, kiwifruit, lettuce, leek, lemon, lime, pine, maize, mango, melon, millet, mushroom, nut oat, okra, onion, orange, an ornamental plant or flower or tree, papaya, parsley, pea, peach, peanut, pepper, persimmon, pineapple, plantain, plum, pomegranate, potato, pumpkin, radicchio, radish, rapeseed, raspberry, rice, rye, sorghum, soy, soybean, spinach, strawberry, sugar beet, sugarcane, sunflower, sweet potato, tangerine, tea, tobacco, tomato, a vine, watermelon, wheat, yams and zucchini, or a part thereof.

[0139] According to Acock (1994) and Camara et al. (1997) the first phase of soybean development begins with emergence and ends with the appearance of a flower bud, morphologically distinct in the apical meristem and controlled predominantly by photoperiod. Several studies have shown that reducing photoperiod promotes early flowering in soybean plants (Nagatoshi & Fujita 2019, Jahne et al. 2020, Fang et al. 2021).

[0140] Jahne et al. (2020) evaluated photoperiods of 10, 12 and 16 hours and found that the adoption of longer photoperiods increases the time for soybean plants to start flowering by an average of approximately 7 days. In this study, flowering began at 31 days after planting (DAP) with a 16 h photoperiod, while with 10 and 12 h photoperiods the average time until flowering varied by an average of 24 days. A similar result was observed by Fang et al. (2021). Yamada et al. (2012) and Nagatoshi & Fujita (2019), evaluating the effect of shortening the photoperiod on soybean flowering, found that shorter photoperiods promoted early flowering of soybeans, around 25 days after planting, while conditions under longer photoperiods would be longer than 30 days. In another study, the number of days between sowing and the start of flowering for BRI 6 soybeans decreased from 40-44 to 35 days when the 10-hour photoperiod was used compared to the 12 hphotoperiod (Carpentieri-Pipolo etal. 2014). Long-day conditions extended the duration of the period from emergence to flowering by an average of 28.6% to 48.8% for various soybean cultivars compared to short-day conditions (Camara et al. 1997). Gallino et al. (2022) found a reduction in the cycle from emergence to flowering from 57-76 days under field conditions to 28 days under shorter photoperiods.

[0141] The different photoperiods influenced the duration of flowering for the different cultivars evaluated (FIG. 2 and Table S5). Flowering for the early cultivar lasted between 26 and 33 days, for the semi-early cultivar between 24 and 31 days and for the late cultivar between 22 and 27 days. When using the 08 and 10 h photoperiod, flowering of the early cultivar lasted -26.2 days, resulting in a cycle of 53.6 and 55.6 days respectively. For the semi-early cultivar, flowering took 24.2 and 26.2 days respectively for the 08 and 10 h photoperiods, resulting in a cycle of 54 and 55.6 days respectively. Using the 12 h photoperiod and full sun, the duration of flowering was 32.8 and 32 days respectively for the early cultivar, and 30.4 and 31.0 days for the semi-early cultivar, resulting in a cycle of 63 to 65 days for the 12 h photoperiod and 70 to 72 days for full sun. The duration of flowering for the late cultivar decreased with the increase in daily light, with 26.0, 22.0 and 20.6 days for the 08, 10 and 12 h photoperiod, respectively, and 26.6 days for full sun. Thus, the vegetative and flowering phases lasted 54.4, 54, 65 and 71 days for the 08, 10, 12 h and full sun photoperiods, respectively.

[0142] Compared to full sun, the use of photoperiods of 8 and 10 h reduced the length of the soybean cycle by around 8 to 16 days, regardless of cultivar, while photoperiod 12 h reduced the cycle by 5 to 6 days for early and semi-early cultivars and did not differ for late cultivars. The differences between the effects of photoperiod on the duration of soybean development phases were quite distinct for early and late maturing cultivars, because early maturing soybeans are more insensitive to photoperiod than late maturing ones (Major et al. 1975, Harrison et al. 2021). In addition, the optimum photoperiod of late-maturing soybean cultivars is generally shorter (Major et al. 1975, Setiyono et al. 2007).

[0143] FIGs. 3a-c shows the number of flowers emitted during the reproductive period by soybean plants of early (a), semi-early (b) and late (c) cultivars under the effect of different photoperiods. The highest number of flowers estimated throughout the flowering cycle was observed for the 12 h photoperiod (195.9), followed by full sun (125.9), 10 h photoperiod (86.7) and 08 h photoperiod (58.8) (FIG. 3a) for the early cultivar. There was a similar response for the semi-early cultivar, where the 12 h photoperiod (116) was superior, followed by full sun (98.6), 10 h photoperiod (79.4) and 08 h photoperiod (63.5) (FIG. 3b). For the late cultivar (FIG. 3c), the highest number offlowers was observed for the 12 h photoperiod (199.9), followed by the 10 h photoperiod (147.4), full sun (87.1) and 08 h photoperiod (61.7).

[0144] In addition to the number of flowers accumulated throughout the flowering phase, it was possible to observe variation in the number of daily flowers emitted by the soybean cultivars as a function of the photoperiods adopted (FIG. S8). Plants grown under the 10 and 12 h photoperiods had the greatest variation in the emission of new flowers throughout the cycle, regardless of the cultivar evaluated.

[0145] Evaluating the effect of photoperiod on soybean development, Camara et al. (1997) found that the length of the soybean cycle was extended by an average of 2.3% to 4.0% under long-day conditions, although not as much as that observed for the vegetative period, which was extended by 28.6% to 48.8% under long-day conditions. Increases were also observed in this study (Fig. 2). The use of the technique of accelerating soybean development through photoperiod control reduced the soybean cycle from 142-165 days to 60 days (Gallino etal. 2022) and from 117-127 days to approximately 61-65 days respectively, under controlled conditions (Harrison et al. 2021). Fang et al. (2021) observed that optimizing the photoperiod to 10 h promoted early flowering at 23 days after sowing, reaching physiological maturity at 77 days. This number of days between stages can also vary depending on the maturity group and cultivar used (Purcell et al. 2013), as can be seen in FIG. 2, especially with regard to the difference between early and late cultivars5,4, Artificial hybridization

[0146] The hybridization efficiency and number of seeds per pod of the different soybean cultivars classified as early (BRS546), semi-early (BRS531) and late (BRS8381) had a significant response! / ? < 0.05) to the different photoperiods only for the hybridization efficiency of the early cultivar and the number of seeds of the late cultivar (Table S6 and FIG. 4). FIG. 4 shows the efficiency of the artificial hybridization process (a) and number of seeds per pod (b) obtained after artificial hybridization in flowers from different soybean cultivars under the effect of different photoperiods. Bars represent average ± SE (n = 4). Averages followed by the same uppercase letter within each cultivar do not differ according to Tukey's test (p < 0.05).

[0147] Hybridization efficiency was higher in plants under the effect of the 12 h photoperiod and full sun, when compared to the 08 h photoperiod (FIG. 4a). For the semi-early and late cultivars, there was no difference between the photoperiods evaluated, in which the average efficiency was 80.0 and 66.7% for the semi-early and late cultivars, respectively.

[0148] The number of seeds (FIG. 4b) per pod averaged 1.96 for the early and semi-early cultivars, which did not differ according to the photoperiods. For the late cultivar, the highest number of seeds was observed in full sun (2.78) compared to the 08 h photoperiod (1.50). Nagatoshi & Fujita(2019) found a hybridization efficiency of 78.4% and an average of 1.90 seeds per pod. In photoperiod-sensitive short-day crops such as soybeans, long-day conditions hinder the onset of flowering but, can increase carbon accumulation and therefore accelerate seed production (Jahne et al. 2020). However, the shorter photoperiod for the early cultivar reduced hybridization efficiency, possibly due to the lower viability of the pollen grains. These conditions did not affect seed production or negatively affect the ability to meet the minimum of one seed per plant (Harrison et al. 2021).5.5. Seed viability

[0149] The emergence rate, seed weight and seedling weight of the different soybean cultivars classified as early (BRS546), semi-early (BRS531) and late (BRS8381) had a significant response (p < 0.05) to the different photoperiods and seasons evaluated (Table S7). There was a significant interaction between the photoperiods and seasons evaluated (Table S7), except for the emergence rate of the early cultivar. The pattern of seeds harvested and used for the emergence test, for the different cultivars at the different seasons, can be seen in FIGs. S16, S17, S18 and S19.

[0150] The emergence rate of the seeds from the different cultivars as a function of the different harvest seasons and under the effect of different photoperiods are shown in FIGs. 5a, 5b and 5c.

[0151] Percentage of emergence (a, b, c), seed weight (PS) (d, e, f) and seedling weight (SW) (g, h, i) from soybean plants under the effect of different photoperiods and different harvest seasons. Bars represent average ± SE (n = 4). Averages followed by the same uppercase letter between photoperiods and lowercase letters within each photoperiod do not differ according to Tukey’s test ( / ? < 0.05).

[0152] The highest emergence rate was observed for seeds harvested from plants under the effect of the shortest photoperiods (08 and 10 h), regardless of the cultivar used (Table S13). These photoperiods provided emergence above 70%, with an average of approximately 73% for the early cultivar, 78% for the semi-early cultivar and 79% for the late cultivar.

[0153] As for the response of emergence as a function of harvest time, an increasing linear response was observed for the early cultivar (FIG. 5a), with the highest rate observed at 81 DAE. The estimated emergence rates were 94.7, 93.3, 53.0 and 86.7% for the 08, 10, 12 h and full sun photoperiods respectively. The emergence data of the seeds obtained from the semi-early cultivar fitted the linear model for the 10 h photoperiod and the quadratic model for the 12 h photoperiod and full sun as a function of the seed harvest seasons (FIG. 5b). For those collected under the 08 h photoperiod, there was no fit to the models evaluated, which had an average emergence of 80.7%. In the photoperiods whose fit was quadratic, maximum emergence was estimated at 78.5 and 75.7 DAE, with emergence of 68.2 and 72.8% respectively for the 12 h and full sun photoperiods.

[0154] For the late cultivar, the highest emergence rates (FIG. 5c) were observed for the seeds collected at 81 DAE in the 08 and 10 h photoperiods, since they were best explained by the increasing linear model. The estimated emergence values were 100 and 98.0% respectively for the 08 and 10 h photoperiod at 81 DAE. The 12 h photoperiod data fitted the inverse quadratic model, so the highest estimated value was at 81 DAE, reaching 39% emergence. The photoperiod in full sun reached 93.5% emergence, and the maximum value was also estimated for the later harvest season.

[0155] Jahne et al. (2020) found an increase in the germination rate of soybean seeds as the harvest season increased, showing greater germination in more mature seeds than those harvested while they were still immature. In general, they observed average germination of more than 50%, even for those collected at 56 days after sowing (DAS), and maximum germination of -90% at 77 DAS. A similar behavior was observed by Fang et al. (2021) in which the germination percentage of fresh and dry seeds increased with increasing seed maturity. Fang et al. (2021) found that the germination rate of immature dry and fresh seeds harvested at the R6 stage was above 60%, with no difference between them. These results indicate that fresh seeds harvested at the R6 stage with the pod completely filled with still green seeds have a high germination capacity, confirming the results of this study.

[0156] Fang et al. (2021) found that as seed maturity progressed to stage R6 with the pod completely filled with green seeds, seed germination improved significantly in all cultivars.Therefore, instead of drying the seeds after harvesting the fresh pods, direct sowing of seeds harvested at the R6 stage can save drying time, advancing the sowing time of the next generation by 7 to 10 days without decreasing the germination rate of the seeds (Fang et al. 2021). Gallino et al. (2022) found that seeds collected while they were still immature without being dehydrated or dried did not germinate, but when they were dehydrated, even though they were immature, germination was higher than 50%, and there was no difference between early, semi-early and late genotypes. Rosenberg & Rinne (1987) found that after 7 days of drying, immature soybean seeds showed the same germination pattern as naturally matured seeds. Under controlled photoperiod conditions of 12 h, Harrison et al. (2021) found approximately 79% germination of seeds harvested at the R7 stage of maturity. Burris (1973) found that germination of immature seeds was higher than 50% as early as 30 days after flowering, reaching 80%, while in the studies by Adams & Rinne (1981) germination of immature seeds was over 86% and in those by Roumet & Morin (1997) over 73%.

[0157] The weight of the seeds obtained from soybean plants under the effect of different photoperiods can be seen in FIGs. 5d, 5e and 5f. The highest seed weights were observed in theshorter photoperiods (08 h and / or 10 h), when compared to the 12 h photoperiod. For the early cultivar, the highest seed weight was observed at 81 DAE for the 08 h (0.14 g), 12 h (0.06 g) and full sun (0.11 g) photoperiods, while under the 10 h photoperiod the highest seed weight (0.13 g) was observed at 74 DAE (FIG. 5d). For the semi-early cycle plants (FIG. 5e), seed weight was higher under the 10 h photoperiod for seeds harvested at 67 (0.12 g), while at 74 DAE, weight was higher under the 08 and 10 h photoperiods (-0.13 g). There was less variation at 81 DAE, with the 08 h photoperiod (0.13 g) being superior only to the 12 h photoperiod (0.11 g). For the late cultivar (Fig. 5f), the highest seed weight was observed at 81 DAE under photoperiods 08 h (0.14 g), 10 h (0.15 g) and full sun (0.14), while under photoperiod 12 h the results were higher at 74 and 81 DAE (-0.057 g).

[0158] The seedling weight varied according to the photoperiods (Table SI 3), being higher under the shortest photoperiod (08 h) for the early and late cultivars, while for the semi-early cultivar it was higher under the 10 h photoperiod. The response of seedling weight to the different harvest seasons for the different soybean cultivars can be seen in FIGs. 5g, 5h and 5i. The data obtained for the early cultivar under the effect of the 08 and 10 h photoperiod (FIG. 5g) fitted the increasing linear model, with a maximum estimated weight at 81 DAE of 0.95 and 0.72 g respectively. For the 12 h photoperiod, there was no fit to the models used and the plants reached an average seedling weight of 0.267 g, while under full sun the data was better explained by the inverse quadratic model, resulting in 0.90 g at 81 DAE. For the semi-early cultivar, the data fitted the inverse quadratic model (FIG. 5h), with the highest seedling weights observed at 81 DAE, estimated at 1.12, 1.86, 1.08 and 1.14 g respectively for the 08, 10, 12 h and full sun photoperiods. For the late cultivar, the data fitted the increasing linear model (full sun) and the inverse quadratic model (08, 10 and 12 h) (Fig. 5i). Thus, the highest seedling weight was estimated at 81 DAE, at 1.56, 1.07, 0.10 and 0.53 g respectively for the 08, 10, 12 h and full sun photoperiods.

[0159] In early studies by Burris (1973) and Roumet & Morin (1997), it was possible to observe an increase in the mass of soybean seeds with the increase in harvesting time after flowering. They also observed an increase in the dry mass of the seedlings, regardless of the soybean genotype used. Seeds harvested when they were more mature led to seedlings with greater heights (Roumet & Morin 1997) and consequently greater seedling mass. Roumet & Morin (1997) demonstrated that seed maturation and germination capacity are independent of seed mass, and that the production of viable seeds was possible through early germination. In addition, these data show that the germination rate and subsequent growth rate of these immature seeds are comparable to mature seeds, indicating that harvesting and germinating immature seeds can be used to shorten the generation time of soybean plants (Nagatoshi & Fujita 2019). In addition, the use of immatureseeds can result in more than 60% plant recovery, i.e. plants with at least one open trefoil generated from the germination of these collected immature seeds (Roumet & Morin 1997), showing the viability and possibility of generating new plants.5.6. Multivariate analysis and Pearson's correlation

[0160] FIG. 6 shows the principal component analysis (PCA) for biometric (a) and physiological indicators related to gas exchange and photosynthesis (b) of soybean plants of different cultivars under the effect of different photoperiods and different measurement seasons. A: net photosynthetic rate; E: transpiration rate; gs: stomatal conductance; Ci: intercellular CO2 concentration; WUE: instantaneous water use efficiency; PH: plant height; LA: leaf area; APDM: aerial part dry mass; NP: number of pods; NS: number of seeds; RL: root length; RV: root volume; RDM: root dry mass. Principal component analysis (PCA) (FIG. 6) was able to explain 74.9% of the variation for biometric indicators (FIG. 6a) and 76.6% for physiological indicators related to gas exchange (FIG.6b) of soybean plants of different maturity groups and cultivars under the effect of different photoperiods and measurement seasons.

[0161] For the biometric indicators (FIG. 6a) of the soybean plants, it was possible to distinguish or group the treatments (effect of the photoperiods), especially the 08 and 10 h photoperiods. As for the 12 h and full sun photoperiods, they were randomly distributed and could not be grouped together in isolation, an indication that they showed a similar response to the sources of variation evaluated. It was also possible to group the data for the early cultivar (BRS546) in the 12 h photoperiod and full sun, but it was not possible to distinguish between the seasons evaluated.

[0162] The variables plant height (PH), number of pods (NP) and number of seeds (NS) were more related to the early cultivar in the 12 h photoperiod and full sun, while root length (RL) was more related to full sun. The aerial part dry mass (APDM), leaf area (LA), root volume (RV) and root dry mass (RDM) were more related to full sun for the semi -early (BRS531) and late (BRS8381) cultivars. The 08 and 10 h photoperiods were in opposite quadrants to the indicators evaluated, showing an inverse relationship.

[0163] For the physiological indicators evaluated (FIG. 6b) it was not possible to distinguish or group the treatments (effect of photoperiods), except for full sun in pre-flowering and full flowering. The effect of the evaluation seasons was evident by the easy distinction of the groups in pre-flowering, full flowering and post-flowering. As for the soybean cultivars, it was not possible to distinguish response groups, showing that the effect of the sources of variation was similar between them.

[0164] Transpiration rate (E), stomatal conductance (gs) and CO2 intercellular concentration (Ci) were directly related to the photoperiod 08 and 10 h in pre-flowering. While chlorophyll a,chlorophyll b and total chlorophyll were more closely related to the season of full bloom for the same photoperiods (08 and 10 h). The data obtained after flowering in full sun and 12 h photoperiod were the opposite of the gas exchange variables, except for water use efficiency (WUE) and leaf area (LA). The chlorophyll alb ratio had a greater relationship with full sun, in preflowering and in full flowering.

[0165] Principal component analysis was able to explain 86.2% of the variation for chlorophyll a fluorescence data (Fig. S9a). In general, it was not possible to distinguish groups between the sources of variation evaluated, although a close trend can be seen for the data obtained in preflowering. The initial fluorescence (Fo), energy absorption index per reaction center (ABS / RC), and energy dissipation flux in the form of heat per reaction center (Dio / RC) and the quantum efficiency of energy dissipation in the form ($Do) had an opposite tendency to the effective quantum efficiency of photochemical energy conversion (Fv / Fo), maximum quantum efficiency of photosystem II (Fv / Fm), the quantum efficiency of electron transport (yEo) and the performance index photochemical (PIABS) (Fig. S9a). The former being more related to pre-flowering data and the others to the other evaluation seasons.

[0166] According to the PCA results, the variables related to soybean plant development (FIG. 6a) that contributed most to each principal component (PC) were MSR (18.0%) and NP (30.2%) for PCI and PC2, respectively. As for the variables related to gas exchange and photosynthesis (Fig.6b), the variables were total chlorophyll (12.9%) and stomatal conductance (gs) (18.0%) and for the variables chlorophyll a fluorescence (FIG. S9a) were Fv / Fo (12.8%) and Fm (77.9%) for PCI and PC2, respectively.

[0167] The data related to the harvesting of immature seeds (FIG. S9b) were explained by 87.8% of the principal components. In general, it was not possible to distinguish between the soybean cultivars used. Except for the semi-early cultivar (BRS531) under a 10 h photoperiod at 81 DAE, which formed a small, isolated group. The late cultivar (BRS8381) in full sun and 12 h photoperiod (FIG. S9b) at 60 DAE formed a single group, which could be explained by the similar behavior of the cultivars, since there was little or no emergence when harvested at this season (FIG. 5). It was possible to distinguish between the shorter photoperiods (08 and 10 h) and the longer ones (12 h and full sun), showing that the photoperiods influenced the plants' response differently. According to the results of the principal component analysis (PCA), the greatest contribution of the variables was observed for the emergence index (Em) (34.1%) in the principal component 1 and for seedling weight (SW) (63.8%) in the principal component 2. It was also possible to verify that the seed weight (PS) was in the same quadrant as the emergence index (Em), showing that there is a relationship between them, contrary to the results observed by Roumet & Morin (1997) whichdemonstrated that the maturation of the seeds and germination capacity are independent of seed mass.

[0168] Principal component analysis is a technique that groups individuals according to the variation in their characteristics (Hongyu et al. 2015) and is an important tool for verifying the relationship between treatments and variables. Principal component 1 and principal component 2 shall explain at least 70% of the variance in the data (Renher 2002) to be considered significant. Thus, the PCA for the biometric indicators and for the variables related to gas exchange and photosynthesis were well represented by the application of this multivariate analysis technique, since the sum of the components was greater than 74%.

[0169] FIG. 7 shows the Pearson correlations represented in Heatmap obtained between the biometric (a) and physiological (b) variables of soybean cultivars under the effect of different photoperiods and measurement seasons. PH: plant height; APDM: aerial part dry mass; LA: leaf area; NP: number of pods; NS: number of seeds; RL: root length; RDM: root dry mass; RV: root volume; SW: seedling weight; Em: emergence; Chlor.: chlorophyll; R.: Ratio; Total Chlor.: total chlorophyll; Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: effective quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum yield of photosystem II; q / Eo: quantum yield of electron transport; $Do: quantum yield of energy dissipation in the form of heat; PIABS: photochemical performance index; ABS / RC: energy absorption rate per reaction center; Dio / RC: energy dissipation flux in the form of heat per reaction center; A: Net photosynthetic rate; E: Transpiration rate; gs: stomatal conductance; Ci:CO2intercellular concentration; WUE: instantaneous water use efficiency. LA: leaf area.***Significant at the 0.1% level (pO. OOl); **significant at the 1% level (p<0.01); *significant at the 5% level (p<0.05); non-significant ns (p>0.05). The Pearson correlation heatmap between the biometric variables (FIG. 7a) showed positive coefficients for growth and yield data, and negative coefficients for the correlation between biometric data and immature seed harvest data. Most of the correlation coefficients were significant, except for the correlation between RL and PH, and Em and SW versus RL, NP and NS (FIG. 7a and Table S14). The significant correlations between the variables ranged from 0.25 to 0.95 (weak to very high correlation), while for the immature seeds versus biometric variables they ranged from -0.64 to -0.20 (weak to moderate correlation). The correlation between emergence and seedling weight was considered moderate (r = 0.60). The strongest significant correlations (r > 0.70) confirmed the relationships observed in the PCA (Fig.6a), and it was possible to discriminate the effect on the different variables.

[0170] The Pearson correlation heatmap between the physiological variables (FIG. 7b) showed positive and negative coefficients, the vast majority of which were significant, except for thecorrelation between A and the chlorophyll a fluorescence, E and LA data, and between Fm and the chlorophyll a fluorescence and gas exchange variables (FIG. 7b and Table SI 5). The correlation coefficients between the variables with a positive relationship ranged from 0.22 to 0.99 (weak to very high correlation), as did the negative ones, which ranged from -0.22 to -0.99 (weak to very high correlation).

[0171] The strongest positive correlations (r > 0.90) were observed between the chlorophyll a, b and total indices, between $Do and Dio / RC, Fv / Fo and Fv / Fm, Fv / Fo and PIABS, yEo and PIABS, $Do and Dio / RC, ABS / RC and Dio / RC. As for the strongest negative correlations (r > 0.90) were between Chlor, b and R. a I b, Fv / Fo and $Do, Fv / Fo and Dio / RC, Fv / Fm and $Do, Fv / Fm and Dio / RC and between E and WUE. Os

[0172] The non-significant correlation between Fm and the other chlorophyll a fluorescence variables confirms the behavior observed in the PCA (Fig. 6b). In general, the heatmaps (FIG. 7) and Pearson's correlation coefficients (Table S14 and S15) reflect the results obtained in the PCA, confirming the groupings and distinctions observed.

[0173] Pearson's correlation analysis resulted in coefficients ranging from negligible correlation (0.00 < r < 0.10, non-significant) to very strong correlation (0.90 < r < 1.00), both positively and negatively (Schober et al. 2018). Most of the time, the correlation coefficients for the physiological variables were considered significant (p < 0.05), ranging from moderate to very strong (0.40 < r <1.00) positive or negative (Schober et al. 2018). The correlations between the biometric variables, although significant, were mostly negligible to moderate (0.00 < r < 0.70) (Schober et al. 2018). 6. AGRONOMIC IMPLICATIONS

[0174] Using conventional breeding methods takes around 5 to 10 years to develop the new crop, 3 to 5 years of field trials and 1 to 3 years to release the cultivar, i.e. the process ranges from 9 to 18 years. However, speed breeding method can average around 1 to 2 years to develop the new crop, 3 to 5 years in field trials and 1 to 3 years to release the cultivar, ranging from 5 to 10 years (Samatara et al. 2022). This reduction in breeding time is possible due to the possibility of obtaining a greater number of generations during the year using the speed breeding method (Jahne et al. 2020, Wanga et al. 2021, Bhatta et al. 2021, Samatara et al. 2022). Obtaining up to five generations per year in a rapid reproduction system will lead to approximately double the annual genetic gain (Jahne et al. 2020). This method is therefore an excellent technique for obtaining more productive cultivars adapted to different climatic conditions in the short term, guaranteeing food security for the world's population.

[0175] In addition, the use of short-day conditions in growth chambers, together with the controlled dehydration of seeds collected while still immature, favors the reduction of the duration of the cropcycle by about 50% when compared to field conditions, shortening even more the generation time of soybean plants without affecting plant vigor (Nagatoshi & Fujita 2019, Gallino et al. 2022). 7. CONCLUSIONS

[0176] Photoperiod promoted changes in the vegetative development of soybean plants, but without causing negative changes in their physiology (photochemical parameters and gas exchange). In addition, the shorter photoperiods accelerated plant development, bringing flowering forward in the shortest photoperiod (08 h) to around 27 to 28 days after emergence.

[0177] The shorter photoperiod altered the length of the vegetative phase and the duration of flowering of the soybean plants for the different cultivars. In addition, there was a change in the number of flowers produced during the reproductive phase. The shorter photoperiod reduced the time to the start of flowering by between 10 and 16 days when compared to full sun. The greatest reductions in the start of flowering were observed for the late cultivar, which reduced flowering by 16 days using the 08 h photoperiod, when compared to the 12 h photoperiod and full sun.

[0178] Harvesting immature seeds proved to be efficient for producing new generations, since they had good emergence rates, which was influenced by the photoperiod. In addition, there was a different response between the cultivars, especially in the 12 h photoperiod.

[0179] Brazil is currently the largest producer of soybeans, and the crop has become one of the main sources of income in agribusiness. In view of this, the search for increasingly productive plants is one of the main efforts of breeding programs. However, the speed with which new cultivars are launched on the market is a bottleneck for plant breeding. In this sense, this work aims to describe the use of a growth chamber for growing soybeans using LED lamps and a protocol that makes it possible to accelerate the soybean crop cycle. With the use of the growth chamber and the Speed Breeding protocol, 66 days after planting, all the pods can be harvested and after drying, new plantings can be made. The construction of the growth chamber is a low-cost solution and the proposed Speed Breeding protocol can help speed up the development and selection of new traits and cultivars.ADDITIONAL TABLESTable S2. F values and significance level of the analysis of variance for the biometric data of different soybean cultivars as a function of different photoperiods and measurement seasonsEarly = BRS546 (GM 6.0) _Variation Source AP APDM LA NP Treatment 1135.0*** 143 9*** 92 1*** 53.5*** Season 91.4*** 12.9*** 29.0*** 2.75ns Treatment x Season 37.3*** 0.387ns 1.69ns 349*** CV(%) 2.40 19.8 20.5 19.1 Early = BRS546 (GM 6.0Variation Source NS RL RDM RV Treatment 78.8*** 11.2*** 762.8*** 203.6*** Season 0.018ns 11.6*** 24.2*** 6.20** Treatment x Season 951*** 437*** 31.8*** 10.5*** CV(%) 17.6 6.57 9.84 13.7 Semi-early = BRS531 (GM 7.3)Variation Source AP APDM LA NP Treatment 262.7*** 82.6*** 62.7*** 10.7*** Season 47.1*** 2.27ns 15.9*** 17.9***Treatment x Season 64.3*** 0.786ns 2.61ns 13.8***CV(%) 1.68 34.9 31.9 20.0 Semi-early = BRS531 (GM 7.3)Variation Source NS RL RDM RV Treatment 173*** 22.9*** 689.7*** 563.2*** Season 16.1*** 10.4*** 18.2*** 170*** Treatment x Season 11.9*** 8.45*** 452*** 8.24*** CV (%) 20.8 7.85 11.6 11.1 Late = BRS 8381 (GM 8.3)Variation Source AP APDM LA NP Treatment 537.6*** 297.3*** 187.6*** 9.11*** Season 215.6*** 2.26ns 15.9*** 67.7*** Treatment x Season 59.8*** 11.2*** 1.68ns 9 10*** CV (%) 3.20 14.5 17.8 22.9 Late = BRS 8381 (GM 8.3)Variation Source NS RL RDM RV Treatment 11.2*** 13.9*** 368.1*** 219.7*** Season 42.3*** 5.60** 21.5*** 13.7*** Treatment x Season 5.83** 4.86*** 15.7*** 4.73*** CV (%) 25.6 5.91 12.3 15.0 CV: coefficient of variation; PH: plant height; APDM: aerial part dry mass; LA: leaf area; NP: number of pods; NS: number of seeds; RL: root length; RDM: root dry mass; RV: root volume. ***Significant at the 0.1% level (p<0.001); ** significant at the 1% level (p<0.01); *significant at the 5% level (p<0.05);nsnot significant (p>0.05).Table S3. F values and significance level of the analysis of variance for gas exchange data and chlorophyll indices of different soybean cultivars as a function of different photoperiods and measurement seasons.Early = BRS546 (GM 6.0) _Variation. „ „...„IC„ A E Ci gs WUE SourceTreatment 0.31ns 1.24ns 0.71ns 3.28* 0.29ns Season 0.05ns 474.1*** 40.1*** 154.8*** 100.7*** Treatment 5.39*** 5.33*** 10.6*** 24.8*** 1.56ns x SeasonCV% 7.65 8.83 1.53 7.97 15.0 Early = BRS546 (GM 6.0)Variation Chlor, a Chlor, b R, a / b Total Chlor.SourceTreatment 38.7*** 1262.1*** 322.0*** 70.7*** 48.7*** Season 256.1*** 880.3*** 825.7*** 4192*** 225.7*** Trpatmpnt 17 7^^^ 10 xicauncni 3 0*** 227*** 1060***x SeasonCV% 4.80 7.70 5.20 5.07 18.9 Semi-early = BRS531 (GM 7.3)Variation Source A E Ci gs WUE Treatment 5.18** 138.5*** 1.09ns 13.7*** 158.6*** Season 5.6** 486.4*** 944*** 80.3*** 715.4*** Treatment x Season 22.7*** 5.19*** 6.53*** 4.64** 33.9*** CV% 4.18 8.10 2.61 12.6 7.49 Semi-early = BRS531 (GM 7.3)Variation Source Chlor, a Chlor, b R, a / b Total Chlor. LA Treatment 29.6*** 406.3*** 191.0*** 1937*** 154*** Season 160.5*** 221.7*** 273.3*** 199.3*** 335.0*** Treatment x Season 4.16** 3.69** 35.4*** 3.96** 328*** CV% 5.11 13.6 7.99 6.99 15.2 Late = BRS 8381 (GM 8.3)Variation Source A E Ci gs WUE Treatment 2.78ns 1.56ns 22.2*** 2.61ns 0.86ns Season 3.34* 312.5*** 51.1*** 43.2*** 258.3*** Treatment x Season 2.83* 2.85* 35.9*** 7.41*** 10.1*** CV% 8.03 11.0 2.12 16.1 10.2 Late = BRS 8381 (GM 8.3)Variation Source Chlor, a Chlor, b R, a / b Total Chlor. LA Treatment 26.3*** 545.4*** 90.6*** 226.6*** 30.5*** Season 212.8*** 408.6*** 272.3*** 318.8*** 282.8*** Treatment x Season 9.66*** 49.9*** 29.2*** 7.33*** 26.5*** CV% 4.82 11.6 7.86 6.26 16.6 CV: coefficient of variation; A: net photosynthetic rate; E: transpiration rate; gs: stomatal conductance; Ci: intercellular CO2 concentration; WUE: instantaneous water use efficiency. Chlor.: chlorophyll; R.: ratio; AF: leaf area. *** Significant at the 0.1% level (p<0.001); ** significant at the 1% level (p<0.01); * significant at the 5% level (p<0.05);nsnon-significant (p>0.05).Table S4. F values and significance level of the analysis of variance for the chlorophyll a fluorescence data of different soybean cultivars as a function of different photoperiods and measurement seasons.Early = BRS546 (GM 6.0)Variation Source Fo Fm Fv / Fo Fv / Fm \| / Eo Treatment 0.90ns 0.48ns 2.12ns 1.87ns 0.36ns Season 31.5*** 7.04** 21.1** 14.0*** 16.5*** Treatment x Season 1.62ns 2.81* 1.32ns1.60ns 1.09ns CV% 10.5 5.23 13.6 3.89 21.1 Early = BRS546 (GM 6.0)Variation Source $Do PIABS ABS / RC Dio / RC Treatment 1.98ns 0.99ns 1.30ns 1.05ns Season 13.9*** 12.3*** 18.8*** 17.5*** Treatment x Season 1.60ns 1.09ns 2.07ns 0.86ns CV% 11.8 41.5 7.24 20.0Semi-early = BRS531 (GM 7.3)Variation Source Fo Fm Fv / Fo Fv / Fm \| / Eo Treatment 1.13ns 2.17ns 1.65ns 2.99ns 2.73ns Season 49.5*** 13.7*** 36.8*** 38.1*** 30.7*** Treatment x Season 3.24* 1.34ns 3.32* 5.08*** 5.15*** CV% 7.40 6.97 9.84 2.50 11.5 Semi-early = BRS531 (GM 7.3)Variation Source $Do PIABS ABS / RC Dio / RC Treatment 2.78ns 1.15ns 1.91ns 3.74* Season 37.7*** 24.8*** 29.5*** 64.5*** Treatment x Season 4.88*** 2.89* 2.37* 5.46*** CV% 8.56 28.4 6.17 9.34Late = BRS 8381 (GM 8.3)Variation Source Fo Fm Fv / Fo Fv / Fm \| / Eo Treatment 0.69ns 2.58ns 1.53ns 1.75ns 1.34ns Season 36.6*** 3.93* 22.6*** 30.5*** 30.1*** Treatment x Season 4.13** 4.68** 6.50*** 13.0*** 3.74** CV% 7.94 5.13 9.57 2.05 12.1 Late = BRS 8381 (GM 8.3)Variation Source $Do PIABS ABS / RC Dio / RCTreatment 1.93ns 2.60ns 0.93 ns 2.46nsSeason 36.7*** 23.0*** 12.6*** 34.5***Treatment x Season 24.7*** 7.29*** 7.15*** 24.2***CV% 5.63 23.5 4.55 8.45CV: coefficient of variation; Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: effective quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum yield of photosystem II; \| / Eo: electron transport quantum yield; < J> Do: quantum yield of energy dissipation in the form of heat; PIABS: photochemical performance index; ABS / RC: energy absorption rate per reaction center; Dio / RC: energy dissipation flow in the form of heat per reaction center. *** Significant at the 0.1% level (p<0.001); ** significant at the 1% level (p<0.01); *significant at the 5% level (p<0.05);nsnon-significant (p>0.05).Table S5. Number of days (average ± standard error) until the start of flowering, duration of flowering and cycle length of soybean cultivars under the effect of different photoperiods.Days until floweringCultivarTreatment Early (BRS 546) Semi-early (BRS 531) Late (BRS 8381) Photoperiod 08 h 27.6±0.25 D 29.8±0.37 C 28.4±0.60 C Photoperiod 10 h 29.2±0.58 C 29.4±0.51 C 32.0±0.55 B Photoperiod 12 h 32.2±0.37 B 32.8±0.37 B 44.4±0.51 A Full sun 38.0±0.00 A 40.8±0.58 A 44.4±0.40 A CV (%) 2.31*** 2.83*** 2.79***Days in floweringCultivarTreatment Early (BRS 546) Semi-early (BRS 531) Late (BRS 8381) Photoperiod 08 h 26.0±0.55 B 24.2±0.97 B 26.0±0.45 A Photoperiod 10 h 26.4±0.81 B 26.2±0.80 B 22.0±0.55 B Photoperiod 12 h 32.8±0.37 A 30.4±0.75 A 20.6±0.51 B Full sun 32.0±0.55 A 31.0±0.45 A 26.6±0.40 A CV (%) 4.03*** 5.47*** 4.03***Cycle durationCultivarTreatment Early (BRS 546) Semi-early (BRS 531) Late (BRS 8381) Photoperiod 08 h 53.6±0.51 D 54.0±1.05 C 54.4±0.25 C Photoperiod 10 h 55.6±0.25 C 55.6±0.60 C 54.0±0.00 C Photoperiod 12 h 65.0±0.00 B 63.2±0.97 B 65.0±0.00 B Full sun 70.0±0.55 A 71.8±0.20 A 71.0±0.00 A CV (%) 1.29*** 2.55*** 0.40*** CV: coefficient of variation; ***Significant at 0.1% (pO. OOl); **significant at 1% (p<0.01); *significant at 5% (p<0.05); non-significant (p>0.05).Table S6. P values and significance level of the analysis of variance for the hybridization data of different soybean cultivars as a function of different photoperiods and measurement seasons.Early = BRS546 (GM 6.0)Variation Source Efficiency QS Treatment 0.0172* 0.1602ns CV% 111.6 32.6Semi-early = BRS531 (GM 7.3)Variation Source Efficiency QS Treatment 0.1078ns 0.2040ns CV% 106.9 31.5Late = BRS 8381 (GM 8.3)Variation Source Efficiency QS Treatment 0.0693ns 0.0253* CV% 117.3 27.3CV: coefficient of variation; QS: quantity of seeds, ***Significant at the 0.1% level (p<0.001); **significant at the 1% level (p<0.01); *significant at the 5% level (p<0.05); “ non-significant (p>0.05).Table S7. F values and significance level of the analysis of variance for the emergence data of different soybean cultivars as a function of different photoperiods and measurement seasons. _Early = BRS546 (GM 6.0)Variation Source Emergence PS SW Treatment 52.7*** 451 4*** 26.1*** Season 129.7*** 158.8*** 107.5*** Treatment x Season 0.79ns 12.1*** 197*** CV% 17.3 5.04 23.5Semi-early = BRS531 (GM 7.3)Variation Source Emergence PS SW Treatment 32.6*** 111.2*** 7.45*** Season 93.7*** 54.5*** 131.0*** Treatment x Season 9.40*** 17.5*** 5.41** CV% 19.1 5.01 36.1Late = BRS 8381 (GM 8.3)Variation Source Emergence PS SW Treatment 139.5*** 166.0*** 64.6*** Season 191.1*** 172.3*** 202.0*** Treatment x Season 13.7*** 13.3*** 20.9*** CV% 18.7 8.92 35.6 CV: coefficient of variation; PS: seed weight; SW: seedling weight. ***Significant at the 0.1% level (pO. OOl); **significant at the 1% level (p<0.01); *significant at the 5% level (p<0.05); “ non-significant (p>0.05),Table S8. Average values ± standard error and fit of regression models for the biometric data of different soybean cultivars as a function of different photoperiods. _Early = BRS546 (GM 6.0)Treatment APDM (g) LA (cm2) NP NS Photoperiod 08 h 4.18±0.34 C (Q) 527.1±59.8 C (L) 25.5±1.00 B (Q) 47.7±2.37 B (Q) Photoperiod 10 h 5.73±0.40 C (Q) 654.4±70.8 C (L) 28.8±1.12 B (ns) 60.4±2.40 B (Q) Photoperiod 12 h 14.4±0.58 B (Q) 1372.1±79.1 B (L) 53.3±2.79 A (Q) 120.0±5.56 A (Q) Full sun 18.2±0.93 A (Q) 1675.9±72.6 A (Q) 52.6±3.68 A (Q) 105.7±6.68 A (Q)Semi-early = BRS531 (GM 7.3)Treatment APDM (g) LA (cm2) NP NS Photoperiod 08 h 3.65±0.49 C (ns) 524.2±70.2 C (L) 27.5±1.10 C (ns) 49.2±1.84 C (ns) Photoperiod 10 h 5.55±0.52 C (ns) 646.4±111 C (L) 31.4±1.27 BC (Q) 66.8±5.13 B (Q) Photoperiod 12 h 14.3±0.67 B (ns) 1477.5±130 B (L) 41.3±1.72 A (Q) 85.9±3.86 A (Q) Full sun 27.2±2.17 A (ns) 2345.0±162 A (ns) 36.3±4.03 AB (Q) 62.1±7.23 BC (L)Late = BRS 8381 (GM 8.3)Treatment APDM (g) LA (cm2) NP NS Photoperiod 08 h 2.89±0.22 C (L) 428.6±57.1 C (L) 24.1±1.28 B (Q) 49.8±2.51 B (ns) Photoperiod 10 h 8.87±0.69 B(Q) 961.7±69.9 B (Q) 37.8±1.76 A (Q) 81.0±4.18 A (Q) Photoperiod 12 h 19.8±0.82 A (L) 2474.2±56.0 A (ns) 35.2±4.53 A (L) 78.3±8.68 A (L) Full sun 21.1±0.63 A (ns) 2303.2±128 A (Q) 35.7±4.06 A (Q) 88.9±10.1 A (Q) APDM: aerial part dry mass; LA: leaf area; NP: number of pods; NS: number of seeds. Uppercase letters compare the means of the treatments in the columns. Averages followed by the same uppercase letter in the columns do not differ according to Tukey's test at the 5% (p<0.05) probability level. Q: quadratic; L: linear;ns: no adjustment.Table S9. Chlorophyll indices (average ± standard error) of different soybean cultivars under the effect of different photoperiods at different measurement seasons.Early = BRS546 (GM 6.0) _- Chlorophyll a - Season3Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 37.5±1.01 cB 46.4±0.67 bAB 53.3±0.66 aA 45.7±1.41 A Photoperiod 10 h 40.2±0.93 cB 48.3±0.38 bA 52.4±1.11 aA 46.9±1.17 A Photoperiod 12 h 45.0±0.73 bA 45.2±1.34 bB 51.4±0.23 aA 47.2±0.79 A Full sun 32.9±0.71 cC 38.8±0.55 bC 50.9±0.85 aA 40.8±1.61 B Average 38.9±0.88 c 44.7±0.75 b 52.0±0.41 a- A / b Ratio - Photoperiod 08 h 3.84±0.05 aB 2.55±0.05 bB 2.31±0.03 cB 2.90±0.14 B Photoperiod 10 h 3.31±0.05 aC 2.39±0.03 bB 2.42±0.06 bAB 2.70±0.09 C Photoperiod 12 h 3.11±0.05 aC 2.52±0.11 bB 2.39±0.04 bAB 2.67±0.08 C Full sun 5.95±0.09 aA 3.45±0.05 bA 2.59±0.07 cA 3.99±0.30 A Average 4.06±0.21 a 2.73±0.08 b 2.43±0.03 cEarly = BRS546 (GM 6.0)- Chlorophyll b - SeasonTreatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 9.78±0.35 cC 18.2±0.47 bB 23.1±0.35 aA 17.1±1.17 A Photoperiod 10 h 12.2±0.39 bB 20.2±0.34 aA 21.7±0.72 aAB 18.0±0.92 A Photoperiod 12 h 14.5±0.28 cA 18.1±0.75 bAB 21.6±0.38 aB 18.0±0.67 A Full sun 5.53±0.11 cD 11.3±0.28 bC 19.8±0.74 aB 12.2±1.25 B Average 10.5±0.61 c 16.9±0.65 b 21.6±0.35 a- Total chlorophyll - Photoperiod 08 h 47.3±1.35 cC 64.7±1.06 bAB 76.4±0.90 aA 62.8±2.57 A Photoperiod 10 h 52.3±1.29 cB 68.6±0.70 bA 74.1±1.70 aAB 65.0±2.06 A Photoperiod 12 h 59.5±0.85 bA 63.3±1.80 bB 73.0±0.52 aAB 65.3±1.36 A Full sun 38.5±0.81 cD 50.1±0.80 bC 70.8±1.49 aB 53.1±2.85 B Average 49.4±1.47 c 61.7±1.37 b 73.6±0.70 aSemi-early = BRS531 (GM 7.3)- Chlorophyll a - Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 38.9±0.62 cB 45.4±1.02 bA 50.6±1.31 aA 45.0±1.15 B Photoperiod 10 h 42.5±1.03 cA 48.0±0.76 bA 52.5±0.87 aA 47.7±0.98 A Photoperiod 12 h 44.7±0.80 bA 45.7±0.87 bA 52.9±0.56 aA 47.8±0.87 A Full sun 35.7±0.58 cB 39.9±0.79 bB 50.1±1.03 aA 41.9±1.34 C Average 40.5±0.72 c 44.8±0.68 b 51.5±0.51 a -a / t> Ratio - Photoperiod 08 h 3.61±0.11 aB 2.83±0.08 bB 2.47±0.10 cAB 2.96±0.11 B Photoperiod 10 h 3.39±0.09 aBC 2.59±0.08 bB 2.28±0.12 bB 2.75±0.11 C Photoperiod 12 h 3.14±0.05 aC 2.85±0.10 aB 2.28±0.05 bB 2.75±0.08 C Full sun 5.99±0.09 aA 4.38±0.16 bA 2.70±0.11 cA 4.36±0.29 AAverage 4.03±0.21 a 3.16±0.14 b 2.43±0.05 cSemi-early = BRS531 (GM 7.3)- Chlorophyll b - Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 10.9±0.41 cB 16.2±0.77 bA 20.8±1.27 aB 16.0±0.98 B Photoperiod 10 h 12.6±0.59 cAB 18.7±0.72 bA 23.6±1.44 aAB 18.3±1.08 A Photoperiod 12 h 14.3±0.44 bA 16.2±0.77 bA 23.3±0.70 aA 17.9±0.89 A Full sun 5.96±0.14 cC 9.18±0.35 bB 18.8±1.14 aB 11.3±1.20 C Average 10.9±0.60 c 15.1±0.71 b 21.6±0.66 a Total chlorophyll Photoperiod 08 h 49.8±0.95 cB 61.7±1.77 bA 71.4±2.56 aA 60.9±2.11 B Photoperiod 10 h 55.1±1.60 aAB 66.7±1.41 bA 76.0±2.23 aA 65.9±2.03 A Photoperiod 12 h 59.0±1.22 bA 61.9±1.62 bA 76.2±1.23 aA 65.7±1.74 A Full sun 41.6±0.69 cC 49.1±0.95 bB 68.9±2.13 aA 53.2±2.52 C Average 51.4±1.29 c 59.8±1.36 b 73.1±1.14 a Late = BRS8381 (GM 8.3) - Chlorophyll a - Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 40.1±0.60 cB 46.7±0.95 bA 52.9±0.82 aA 46.5±1.18 A Photoperiod 10 h 41.8±0.95 cAB 46.7±0.72 bA 53.2±0.53 aA 47.3±1.06 A Photoperiod 12 h 44.5±0.51 cA 47.4±1.10 bA 52.6±1.06 aA 47.6±0.75 A Full sun 34.8±0.66 cC 39.4±0.86 bB 52.6±0.82 aA 42.2±1.64 B Average 40.3±0.72 c 45.0±0.73 b 52.4±0.45 a -a / t> Ratio - Photoperiod 08 h 3.53i0.10 aB 2.55i0.09 bB 2.30i0.07 bB 2.79iO.12 B Photoperiod 10 h 3.37i0.13 aB 2.70i0.07 bB 2.29i0.03 cB 2.78i0.11 B Photoperiod 12 h 3.24iO.12 aB 2.60i0.09 bB 2.47i0.08 bAB 2.77i0.09 B Full sun 5.72iO.13 aA 3.63i0.07 bA 2.63i0.05 cA 3.97iO.27 A Average 3.96i0.19 a 2.87i0.09 b 2.41i0.04 c Late = BRS8381 (GM 8.3)Season Treatment Pre-flowering Full flowering Post- flowering Average Photoperiod 08 h 11.4±0.46 cB 18.5±0.88 bA 23.2±0.99 aAB 17.7±1.10 A Photoperiod 10 h 12.6±0.68 cAB 17.4±0.55 bA 23.3±0.44 aA 17.8±0.97 A Photoperiod 12 h 13.9±0.61 bA 18.4±0.96 aA 20.9±1.13 aB 17.7±0.79 A Full sun 6.10±0.15 cC 10.9±0.38 bB 20.1±0.71 aB 12.4±1.24 B Average 11.0±0.59 c 16.3±0.67 b 21.9±0.48 a Total chlorophyll- Photoperiod 08 h 51.5±1.04 cB 65.1±1.67 bA 76.1±1.76 aA 64.2±2.26 A Photoperiod 10 h 54.4±1.55 cAB 64.1±1.13 bA 76.6±0.86 aA 65.0±2.01 A Photoperiod 12 h 58.4±1.05 bA 65.8±2.04 aA 71.9±2.11 aA 65.4±1.52 A Full sun 40.9±0.74 cC 50.2±1.20 bB 72.7±1.71 aA 54.6±2.87 BAverage 51.3±1.28 c 61.3±1.37 b 74.3±0.88 aaPre-flowering (Stage V6), full flowering (Stage R2), and post-flowering (Stage R4), respectively. Uppercase letters compare the means of the treatments in the columns and lowercase letters compare the means of the seasons in the rows. Averages followed by the same uppercase or lowercase letter in the rows or columns do not differ according to Tukey's test at the 5% (p<0.05) probability level.Table S10. Indicators related to chlorophyll a fluorescence (average ± standard error) for the early soybean cultivar (BRS 546) under the effect of different photoperiods at different measurement seasons.- Fo - Season3Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 159.7±8.74 117.0±2.27 113.1±5.19 129.9±7.10 Photoperiod 10 h 157.6±9.86 112.0±7.10 102.3±6.24 127.6±8.35 Photoperiod 12 h 144.3±7.58 123.7±9.15 114.8±8.11 123.9±5.72 Full sun 134.6±11.6 126.7±5.94 99.9±4.58 120.4±6.10 Average 149.1±5.02 a 119.8±3.31 b 107.5±3.23 b- Fv / Fo - Photoperiod 08 h 2.35±0.21 3.53±0.10 3.07±0.13 2.98±0.16 Photoperiod 10 h 2.32±0.19 3.61±0.11 3.41±0.24 3.11±0.20 Photoperiod 12 h 2.37±0.23 3.22±0.28 3.41±0.25 2.99±0.19 Full sun 2.88±0.51 3.32±0.29 4.09±0.13 3.43±0.23 Average 2.48±0.15 b 3.42±0.10 a 3.49±0.13 a- yEo - Photoperiod 08 h 0.17±0.02 0.34±0.03 0.33±0.04 0.27±0.02 Photoperiod 10 h 0.19±0.01 0.34±0.02 0.37±0.02 0.30±0.02 Photoperiod 12 h 0.21± 0.04 0.31±0.03 0.33±0.03 0.28±0.02 Full sun 0.27±0.07 0.31±0.03 0.32±0.02 0.29±0.02 Average 0.21±0.02 b 0.32±0.01 a 0.34±0.01 a- PIABS - Photoperiod 08 h 0.25±0.06 1.03±0.20 0.87±0.18 0.71±0.13 Photoperiod 10 h 0.27±0.05 1.06±0.13 1.26±0.27 0.86±0.16 Photoperiod 12 h 0.37±0.14 0.84±0.21 0.91±0.10 0.71±0.11 Full sun 0.79±0.35 0.81±0.18 1.20±0.21 0.93±0.15 Average 0.42±0.10 b 0.93±0.09 a 1.06±0.10 a- Dio / RC - Photoperiod 08 h 0.95±0.09 0.60±0.01 0.71±0.04 0.75±0.05 Photoperiod 10 h 0.98±0.09 0.58±0.03 0.63±0.06 0.73±0.06 Photoperiod 12 h 0.95±0.10 0.68±0.07 0.67±0.12 0.77±0.06 Full sun 0.84±0.16 0.68±0.05 0.45±0.03 0.66±0.07 Average 0.93±0.05 a 0.63±0.03 b 0.62±0.04 b- Fm - SeasonTreatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 530.1±11.8 aA 529.5±8.69 aA 457.7±9.68 bAB 505.8±11.5 Photoperiod 10 h 518.2±15.2 aA 514.5±13.8 aA 447.7±4.61 bB 493.2±13.0 Photoperiod 12 h 481.0±7.41 aA 514.3±23.2 aA 500.3±10.6 bAB 498.6±7.04 Full sun 504.9±25.4 aA 505.0±20.8 aA 506.8±14.5 aA 505.6±10.8 Average 508.6±8.70 a 515.8±8.19 a 477.9±8.17 b- Fv / Fm - Photoperiod 08 h 0.70±0.02 0.78±0.01 0.75±0.01 0.74±0.01 Photoperiod 10 h 0.70±0.02 0.78±0.01 0.77±0.01 0.75±0.01Photoperiod 12 h 0.70±0.02 0.76±0.02 0.77±0.01 0.74±0.01 Full sun 0.73±0.04 0.77±0.02 0.80±0.01 0.76±0.01 Average 0.71±0.01 b 0.77±0.01 a 0.77±0.01 a- ^Do - Photoperiod 08 h 0.30±0.02 0.22±0.01 0.25±0.01 0.26±0.01 Photoperiod 10 h 0.30±0.02 0.21±0.01 0.23±0.01 0.25±0.01 Photoperiod 12 h 0.30±0.02 0.24±0.02 0.23±0.01 0.26±0.01 Full sun 0.27±0.04 0.24±0.02 0.20±0.01 0.23±0.01 Average 0.30±0.01 a 0.23±0.01 b 0.23±0.01 b- ABS / RC - Photoperiod 08 h 3.13±0.11 2.70±0.01 2.89±0.13 2.90±0.07 Photoperiod 10 h 3.20±0.13 2.68±0.11 2.72±0.15 2.87±0.10 Photoperiod 12 h 3.13±0.15 2.53±0.13 2.58±0.05 2.85±0.09 Full sun 3.02±0.19 2.86±0.07 2.29±0.08 2.72±0.11 Average 3.12±0.07 a 2.77±0.04 b 2.62±0.07 b3Pre-flowering (Stage V6), full flowering (Stage R2), and post-flowering (Stage R4), respectively. Uppercase letters compare the means of the treatments in the columns and lowercase letters compare the means of the seasons in the rows. Averages followed by the same uppercase or lowercase letter in the rows or columns do not differ according to Tukey's test at the 5% (p<0.05) probability level. Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: effective quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum yield of photosystem II; \| / Eo: electron transport quantum yield; <j)Do: quantum yield of energy dissipation in the form of heat; PIABS: performance index photochemical; ABS / RC: energy absorption rate per reaction center; Dio / RC: energy dissipation flow in the form of heat per reaction center.Table S11. Indicators related to chlorophyll a fluorescence (average ± standard error) for the semi- early soybean cultivar (BRS 531) under the effect of different photoperiods at different measurement seasons.- Fo - Season3Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 127.2±3.41 aB 110.7±2.49 bA 102.8±4.81 bA 113.6±3.62 Photoperiod 10 h 139.8±1.60 aAB 112.5±4.83 abA 97.1±1.68 bA 116.5±5.57 Photoperiod 12 h 152.8±7.00 aA 106.0±6.67 bA 101.3±4.59 bA 121.1±7.57 Full sun 126.4±3.54 aB 118.3±6.34 abA 107.6±7.99 bA 117.4±4.00 Average 136.6±3.40 a 112.6±2.56 b 102.2±2.55 c - Fv / Fo - Photoperiod 08 h 2.76±0.23 bAB 3.93±0.11 aA 3.94±0.29 aA 3.54±0.20 Photoperiod 10 h 2.91±0.10bAB 4.20±0.08 aA 3.76±0.19 aA 3.62±0.18 Photoperiod 12 h 2.18±0.17 bB 3.99±0.13 aA 3.68±0.12 aA 3.28±0.25 Full sun 3.40±0.20 aA 3.66±0.15 aA 3.55±0.38 aA 3.54±0.14 Average 2.81±0.14 b 3.94±0.07 a 3.73±0.13 a - yEO- Photoperiod 08 h 0.27±0.03 bB 0.38±0.01 aA 0.44±0.01 aA 0.36±0.02 Photoperiod 10 h 0.27±0.01 bB 0.40±0.01 aA 0.41±0.01 aA 0.36±0.02 Photoperiod 12 h 0.20±0.02 bB 0.37±0.02 aA 0.38±0.01 aA 0.32±0.02 Full sun 0.37±0.03 aA 0.37±0.03 aA 0.35±0.05 aA 0.36±0.02 Average 0.28±0.01 b 0.38±0.01 a 0.39±0.01 a - PIABS - Photoperiod 08 h 0.55±0.11 bAB 1.41±0.14 aA 1.94±0.29 aA 1.30±0.20 Photoperiod 10 h 0.55±0.03 bAB 1.66±0.15 aA 1.64±0.21 aA 1.28±0.17 Photoperiod 12 h 0.30±0.06 bB 1.48±0.20 aA 1.32±0.06 aA 1.03±0.17 Full sun 1.16±0.24 aA 1.26±0.24 aA 1.22±0.36 aA 1.21±0.15 Average 0.64±0.10 b 1.45±0.09 a 1.53±0.14 a - Dio / RC - Photoperiod 08 h 0.71±0.02 aB 0.52±0.01 bA 0.52±0.05 bA 0.58±0.03 AB Photoperiod 10 h 0.74±0.03 aB 0.49±0.02 bA 0.48±0.01 bA 0.57±0.04 B Photoperiod 12 h 0.91±0.02 aA 0.49±0.03 bA 0.55±0.02 bA 0.65±0.06 A Full sun 0.67±0.05 aB 0.61±0.05 aA 0.58±0.04 aA 0.62±0.03 AB Average 0.76±0.02 a 0.53±0.02 b 0.53±0.02 b - Fm - Season Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 508.6±8.49 545.7±19.2 504.2±15.2 519.5±9.62 Photoperiod 10 h 547.3±20.4 584.0±16.8 499.5±22.2 543.6±14.7 Photoperiod 12 h 483.6±10.5 541.8±24.7 474.6±23.6 499.9±14.0 Full sun 554.2±10.5 566.3±27.7 448.9±35.7 523.1±21.2 Average 523.4±9.53 a 559.4±11.0 a 481.8±12.7 b - Fv / Fm - Photoperiod 08 h 0.73±0.01 bB 0.79±0.01 aA 0.79±0.01 aA 0.77±0.01 Photoperiod 10 h 0.74±0.01 aAB 0.80±0.01 aA 0.78±0.01 aA 0.78±0.01 Photoperiod 12 h 0.68±0.01bC 0.80±0.01 aA 0.78±0.01 aA 0.76±0.02 Full sun 0.77±0.01 aA 0.78±0.01 aA 0.77±0.01 aA 0.78±0.01 Average 0.73±0.01 b 0.80±0.01 a 0.79±0.01 a -(|i|)o - Photoperiod 08 h 0.27±0.02 aB 0.20±0.01 bA 0.21±0.01 bA 0.23±0.01 Photoperiod 10 h 0.26±0.01 aB 0.19±0.01 bA 0.21±0.01 bA 0.22±0.01 Photoperiod 12 h 0.32±0.02 aA 0.20±0.01 bA 0.21±0.01 bA 0.24±0.01 Full sun 0.23±0.01 aB 0.22±0.01 aA 0.22±0.02 aA 0.22±0.01Average 0.27±0.01 a 0.20±0.01 b 0.21±0.01 b- ABS / RC - Photoperiod 08 h 2.96±0.14 aA 2.54±0.04 bA 2.54±0.10 bA 2.68±0.08 Photoperiod 10 h 2.90±0.03 aA 2.55±0.06 bA 2.36±0.03 bA 2.60±0.07 Photoperiod 12 h 3.24±0.13 aA 2.44±0.10 bA 2.59±0.07 bA 2.75±0.12 Full sun 2.91±0.09 aA 2.80±0.14 aA 2.59±0.12 aA 2.77±0.07 Average 3.00±0.06 a 2.58±0.05 b 2.52±0.05 baPre-flowering (Stage V6), full flowering (Stage R2), and post-flowering (Stage R4), respectively. Uppercase letters compare the means of the treatments in the columns and lowercase letters compare the means of the seasons in the rows. Averages followed by the same uppercase or lowercase letter in the rows or columns do not differ according to Tukey's test at the 5% (p<0.05) probability level. Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: efficient quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum efficiency of photosystem II; \| / Eo: electron transport quantum yield; < J> Do: quantum energy dissipation efficiency in the form of heat; PIABS: photochemical performance index; ABS / RC: energy absorption index per occurrence center; Dio / RC: flow of energy dissipation in the form of heat per center of occurrence.Table S12. Indicators related to chlorophyll a fluorescence (average ± standard error) for the late cultivar (BRS 8381) of soybean under the effect of different photoperiods at different measurement seasons.- Fo - Season3Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 144.2±0.73 aA 113.2±6.19 bAB 107.8±5.82 bA 121.7±5.48 Photoperiod 10 h 141.6±5.25 aAB 115.5±4.73 bAB 95.4±1.97 cA 117.5±6.11 Photoperiod 12 h 135.3±6.44 aAB 105.7±4.40 bB 105.8±2.41 bA 115.6±4.87 Full sun 121.8±5.6 aB 133.2±10.4 aA 103.0±4.50 bA 119.3±5.37 Average 135.7±3.17 a 116.9±4.03 b 102.9±2.16 c - Fv / Fo - Photoperiod 08 h 2.67±0.11 bB 3.75±0.16 aA 3.48±0.13 aA 3.30±0.16 Photoperiod 10 h 2.64±0.03 bB 3.57±0.18 aA 3.56±0.06 aA 3.26±0.14 Photoperiod 12 h 2.81±0.19 bAB 3.94±0.15 aA 3.92±0.17 aA 3.56±0.18 Full sun 3.44±0.34 aA 2.72±0.33 bB 4.05±0.11 aA 3.40±0.22 Average 2.89±0.12 b 3.50±0.16 a 3.76±0.08 a - yEO- Photoperiod 08 h 0.23±0.02 bB 0.34±0.03 aAB 0.38±0.01 aA 0.32±0.02 Photoperiod 10 h 0.23±0.01 bB 0.34±0.02 aAB 0.38±0.01 aA 0.32±0.02 Photoperiod 12 h 0.26±0.02 bAB 0.37±0.02 aA 0.40±0.01 aA 0.34±0.02 Full sun 0.34±0.04 abA 0.27±0.04 bB 0.41±0.02 aA 0.34±0.02 Average 0.27±0.02 c 0.33±0.02 b 0.39±0.01 a - PIABS - Photoperiod 08 h 0.43±0.07 bB 1.15±0.23 aAB 1.21±0.05 aA 0.93±0.13 Photoperiod 10 h 0.42±0.03 bB 1.04±0.18 aAB 1.32±0.09 aA 0.92±0.13 Photoperiod 12 h 0.54±0.09 bB 1.41±0.18 aA 1.49±0.09 aA 1.14±0.15 Full sun 1.39±0.17 aA 0.63±0.22 bB 1.46±0.08 aA 1.16±0.14 Average 0.69±0.12 c 1.05±0.12 b 1.37±0.05 a - Dio / RC - Photoperiod 08 h 0.81±0.03 aA 0.55±0.03 bB 0.61±0.03 bA 0.65±0.04 Photoperiod 10 h 0.81±0.02 aA 0.59±0.04 bB 0.57±0.02 bA 0.66±0.04 Photoperiod 12 h 0.77±0.05 aA 0.49±0.02 bB 0.54±0.02 bA 0.60±0.04 Full sun 0.57±0.04 bB 0.91±0.04 aA 0.50±0.02 bA 0.66±0.06 Average 0.74±0.03 a 0.63±0.04 b 0.55±0.01 c - Fm - Season Treatment Pre-flowering Full flowering Post-flowering Average Photoperiod 08 h 528.3±13.1 abA 536.0±21.3 aA 480.8±10.5 bBC 515.0±11.0 Photoperiod 10 h 514.9±17.3 aA 525.5±9.18 aA 435.2±5.14 bC 491.9±13.6 Photoperiod 12 h 513.3±20.0 aA 521.0±9.67 aA 541.9±14.4 aA 525.4±8.78 Full sun 533.5±18.4 aA 486.7±16.3 aA 519.2±17.2 aAB 513.1±10.8 Average 522.2±8.10 a 517.3±8.22 ab 494.3±11.9 b - Fv / Fm - Photoperiod 08 h 0.73±0.01 bB 0.79±0.01 aA 0.78±0.01 aA 0.76±0.01 Photoperiod 10 h 0.73±0.01 bB 0.78±0.01 aA 0.78±0.01 aA 0.76±0.01 Photoperiod 12 h 0.74±0.01 bB 0.80±0.01 aA 0.80±0.01 aA 0.78±0.01 Full sun 0.77±0.01 bA 0.71±0.01 cB 0.80±0.01 aA 0.76±0.01 Average 0.74±0.01 c 0.77±0.01 b 0.79±0.01 a -(|i|)o - Photoperiod 08 h 0.28±0.01 aA 0.21±0.01 bB 0.22±0.01 bA 0.24±0.01 Photoperiod 10 h 0.28±0.01 aA 0.22±0.01 bB 0.22±0.01 bA 0.24±0.01 Photoperiod 12 h 0.27±0.01 aA 0.21±0.01 bB 0.20±0.01 bA 0.22±0.01 Full sun 0.21±0.01 bB 0.30±0.01 aA 0.20±0.01 bA 0.24±0.01 Average 0.26±0.01 a 0.23±0.01 b 0.21±0.01 c- ABS / RC -Photoperiod 08 h 2.96±0.04 aA 2.58±0.08 bB 2.70±0.07 bA 2.75±0.06 Photoperiod 10 h 2.93±0.05 aA 2.67±0.07 bB 2.59±0.04 bA 2.73±0.05 Photoperiod 12 h 2.90±0.09 aAB 2.44±0.05 bB 2.64±0.02 bA 2.66±0.07 Full sun 2.63±0.06bB 2.96±0.12 aA 2.53±0.08 bA 2.71±0.07 Average 2.86±0.04 a 2.66±0.06 b 2.62±0.03 baPre-flowering (Stage V6), full flowering (Stage R2), and post-flowering (Stage R4), respectively. Uppercase letters compare the means of the treatments in the columns and lowercase letters compare the means of the seasons in the rows. Averages followed by the same uppercase or lowercase letter in the rows or columns do not differ according to Tukey's test at the 5% (p<0.05) probability level. Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: efficient quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum efficiency of photosystem II; \| / Eo: electron transport quantum yield; < J> Do: quantum energy dissipation efficiency in the form of heat; PIABS: photochemical performance index; ABS / RC: energy absorption index per occurrence center; Dio / RC: flow of energy dissipation in the form of heat per center of occurrence.Table S13. Average values ± standard error and fit of regression models for the emergence data of different soybean cultivars as a function of different photoperiods.Early = BRS546 (GM 6.0)Treatment Emergence SW Photoperiod 08 h 75.3±4.79 A (L) 0.63±0.07 A (L) Photoperiod 10 h 71.9±5.29 AB (L) 0.52±0.04 AB (L) Photoperiod 12 h 30.9±4.70 C (L) 0.27±0.03 C (ns) Full sun 63.5±4.91 B (L) 0.46±0.07 B (Q)Semi-early = BRS531 (GM 7.3)Treatment Emergence SW Photoperiod 08 h 80.7±3.42 A (ns) 0.67±0.10 B (Q) Photoperiod 10 h 76.3±4.62 A (L) 1.01±0.18 A (Q) Photoperiod 12 h 48.8±6.67 B (Q) 0.65±0.07 B (Q) Full sun 45.4±6.89 B (Q) 0.59±0.14 B (Q)Late = BRS 8381 (GM 8.3)Treatment Emergence SW Photoperiod 08 h 78.8±4.81 A (L) 0.70±0.12 A (Q) Photoperiod 10 h 80.6±4.71 A (L) 0.49±0.09 B (Q) Photoperiod 12 h 10.4±3.93 C (Q) 0.05±0.02 D (Q) Full sun 51.8±9.34 B (Q) 0.25±0.06 C (L) SW: seedling weight. Uppercase letters compare the means of the treatments in the columns. Averages followed by the same uppercase letter in the columns do not differ according to Tukey's test at the 5% (p<0.05) probability level. Q: quadratic; L: linear;ns: no adjustment.Table S14. Pearson's correlation coefficients and p values between the biometric variables of soybean cultivars under the effect of different photoperiods and measurement seasons.Pearson's correlation coefficientLA AP APDM RL RV RDM NP NS Em SW LA 1.00AP 0.29 1.00APDM 0.90 0.26 1.00RL 0.28 0.13 0.40 1.00RV 0.85 0.33 0.86 0.29 1.00RDM 0.86 0.25 0.87 0.26 0.94 1.00NP 0.35 0.31 0.47 0.37 0.46 0.49 1.00NS 0.39 0.39 0.46 0.27 0.51 0.53 0.95 1.00Em -0.64 -0.40 -0.51 -0.05 -0.44 -0.43 0.02 -0.07 1.00SW -0.48 -0.20 -0.37 0.00 -0.35 -0.35 -0.03 -0.13 0.60 1.00 P-valuesLA AP APDM RL RV RDM NP NS Em SW LA 0,0000AP 0,0000 0,0000APDM 0,0000 0,0003 0,0000RL 0,0001 0,0673 0,0000 0,0000RV 0,0000 0,0000 0,0000 0,0000 0,0000RDM 0,0000 0,0004 0,0000 0,0003 0,0000 0,0000NP 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000NS 0,0000 0,0000 0,0000 0,0001 0,0000 0,0000 0,0000 0,0000Em 0,0000 0,0000 0,0000 0,4535 0,0000 0,0000 0,8122 0,3428 0,0000SW 0,0000 0,0052 0,0000 0,9914 0,0000 0,0000 0,6594 0,0783 0,0000 0,0000 PH: plant height; APDM: aerial part dry mass; LA: leaf area; NP: number of pods; NS: number of seeds; RL: root length; RDM: root dry mass; RV: root volume.Table SI 5. Pearson's correlation coefficients and p values between the physiological variables of soybean cultivars under the effect of different photoperiods and measurement seasons.Pearson correlation coefficientsChlor, a Chlor, b R, a / b Total chlor. Fo Fm Fv / Fo Fv / Fm yEo <|> Do Chlor, a 1,000 Chlor, b 0,966 1,000 R, a / b -0,852 -0,902 1,000 Total chlor. 0.992 0.991 -0.883 1,000 Fo -0,589 -0,604 0,419 -0,601 1,000 Fm -0,378 -0,379 0,278 -0,382 0,354 1,000 Fv / Fo 0,400 0,401 -0,281 0,404 -0,800 0,149 1,000 Fv / Fm 0,417 0,427 -0,301 0,425 -0,808 0,133 0,971 1,000 PHIEO 0,426 0,436 -0,251 0,435 -0,822 0,000 0,888 0,883 1,000 PHIDO -0,400 -0,412 0,279 -0,409 0,800 -0,120 -0,954 -0,987 -0,868 1,000 PIABS 0,387 0,389 -0,215 0,392 -0,789 -0,003 0,902 0,855 0,930 -0,861 ABSRC -0,482,0,491 0,372,0,491 0,865 0,140 -0,825 -0,819 -0,725 0,828 Dio / RC -0,446 -0,462 0,327 -0,457 0,867 -0,039 -0,913 -0,948 -0,837 0,960 E -0,590 -0,613 0,584 -0,606 0,631 0,116 -0,623 -0,619 -0,567 0,597 A 0,035 0,077 -0,055 0,055 -0,044 0,019 0,074 0,053 -0,043 -0,069 Ci -0,379 -0,344 0,309 -0,366 0,374 -0,008 -0,450 -0,406 -0,316 0,401 gs -0,463 -0,448 0,455 -0,460 0,401 0,046 -0,439 -0,437 -0,344 0,415 WUE 0,507 0,538 -0,532 0,526 -0,538 -0,016 0,586 0,576 0,453 -0,561LA 0,528 0,485 -0,468 0,512 -0,527 -0,096 0,552 0,519 0,477 -0,502 Pearson correlation coefficients (cont’d)PIABS ABS / RC Dio / RC E A Ci gs WUE LA Chlor, aChlor, bR, a / bTotal chlor.FoFmFv / FoFv / FmPHIEO PHIDO PIABS 1,000ABSRC -0,779 1,000Dio / RC -0,832 0,906 1,000E -0,520 0,537 0,577 1,000A 0,001 -0,085 -0,071 0,062 1,000Ci -0,320 0,412 0,392 0,530 -0,275 1,000gs -0,335 0,365 0,378 0,832 0,229 0,612 1,000WUE 0,429 -0,493 -0,538 -0,914 0,232 -0,680 -0,744 1,000LA 0,452 -0,520 -0,517 -0,716 0,020 -0,622 -0,655 0,685 1,000 P-valuesChlor, a Chlor, b R, a / b Total chlor. Fo Fm Fv / Fo Fv / Fm yEo <|> Do Chlor, a 0,0000 Chlor, b 0,0000 0,0000 R, a / b 0,0000 0,0000 0,0000 Total chlor. 0,0000 0,0000 0,0000 0,0000 Fo 0,0000 0,0000 0,0000 0,0000 0,0000 Fm 0,0000 0,0000 0,0007 0,0000 0,0000 0,0000 Fv / Fo 0,0000 0,0000 0,0006 0,0000 0,0000 0,0750 0,0000 Fv / Fm 0,0000 0,0000 0,0002 0,0000 0,0000 0,1119 0,0000 0,0000 yEo 0,0000 0,0000 0,0024 0,0000 0,0000 0,9953 0,0000 0,0000 0,0000 <|> Do 0,0000 0,0000 0,0007 0,0000 0,0000 0,1509 0,0000 0,0000 0,0000 0,0000 PIABS 0,0000 0,0000 0,0096 0,0000 0,0000 0,9714 0,0000 0,0000 0,0000 0,0000 ABS / RC 0,0000 0,0000 0,0000 0,0000 0,0000 0,0936 0,0000 0,0000 0,0000 0,0000 Dio / RC 0,0000 0,0000 0,0001 0,0000 0,0000 0,6399 0,0000 0,0000 0,0000 0,0000 E 0,0000 0,0000 0,0000 0,0000 0,0000 0,1677 0,0000 0,0000 0,0000 0,0000 A 0,6793 0,3609 0,5135 0,5115 0,6039 0,8215 0,3755 0,5269 0,6116 0,4127 Ci 0,0000 0,0000 0,0002 0,0000 0,0000 0,9234 0,0000 0,0000 0,0001 0,0000 gs 0,0000 0,0000 0,0000 0,0000 0,0000 0,5878 0,0000 0,0000 0,0000 0,0000 WUE 0,0000 0,0000 0,0000 0,0000 0,0000 0,8459 0,0000 0,0000 0,0000 0,0000LA 0,0000 0,0000 0,0000 0,0000 0,0000 0,2542 0,0000 0,0000 0,0000 0,0000 P-values (cont’d)PIABS ABS / RC Dio / RC E A Ci gs WUE LA Chlor, aChlor, bR, a / bTotal chlor.FoFmFv / FoFv / FmyEo<|> DoPIABS 0,0000ABS / RC 0,0000 0,0000Dio / RC 0,0000 0,0000 0,0000E 0,0000 0,0000 0,0000 0,0000A 0,9865 0,3127 0,3965 0,4616 0,0000Ci 0,0001 0,0000 0,0000 0,0000 0,0009 0,0000gs 0,0000 0,0000 0,0000 0,0000 0,0058 0,0000 0,0000WUE 0,0000 0,0000 0,0000 0,0000 0,0051 0,0000 0,0000 0,0000LA 0,0000 0,0000 0,0000 0,0000 0,8164 0,0000 0,0000 0,0000 0,0000 Chlor: chlorophyll; R.: ratio; Total Chlor.: total chlorophyll; Fo: initial fluorescence; Fm: maximum emitted fluorescence; Fv / Fo: effective quantum yield of photochemical energy conversion; Fv / Fm: maximum quantum yield of photosystem II; \| / Eo: quantum yield of electron transport; < J> Do: quantum yield of energy dissipation in the form of heat; PIABS: photochemical performance index; ABS / RC: energy absorption rate per reaction center; Dio / RC: energy dissipation flux in the form of heat per reaction center; A: Net photosynthetic rate; E: Transpiration rate; gs: stomatal conductance; Ci: CO₂intercellular concentration; WUE: instantaneous water use efficiency. 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Claims

THE CLAIMSWhat is claimed is:

1. A method of accelerating the development of a plant, comprising:an enclosed growth chamber having:at least one rack for holding one or more plants or plant parts potted in one or more containers;one or more light emitting diode (LED) lights situated above the one or more containers containing the plants, wherein the LED lights are contained on a bar or are individually hung above the plants or plant parts; andwhereas the LED lights can be adjusted in a vertical position;allowing the LED lights to remain on continuously for at least an 8 hour photoperiod during each twenty-four hour period; andcontinuously adjusting the LED lights with the height of plant canopy, so that the distance between the LED light and plant canopy is at least 25 centimeters until the one or more plants reach a desired maturity.

2. The method of claim 1, wherein the growth chamber is enclosed with individually or in combination with fabric, glass, metal, or plastic, dry wall or on all sides.

3. The one or more racks of claim 1, wherein said racks are arranged linearly and / or vertically.

4. The method of claim 1, wherein said LED lights comprise at least 30 watts of power and at least 2700 lumens of luminous flux.

5. The method of claim 1, wherein the LED light has a continuous intensity of at least 600 pmol m-2 s-1.

6. The method of claim 1, wherein the LED light has a continuous intensity of at least 700 pmol m-2 s-1.

7. The method of claim 1, wherein the LED light has a continuous intensity of at least 800 pmol m-2 s-1.

8. The method of claim 1, wherein the LED light has a continuous intensity of at least 900 pmol m-2 s-1.

9. The method of claim 1, wherein the LED light has a continuous intensity of at least 1,00 pmol m-2 s-1.

10. The fabric of claim 2, wherein the fabric consists of a double layer of non-woven fabric.

11. The method of claim 1, wherein said plant is alfalfa, apple, apricot, artichoke, asparagus, avocado, banana, barley, beans, beet, blackberry, blueberry, Brassica, broccoli, brussel sprouts, cabbage, canola, carrot, cassava, cauliflower, a cereal, celery, cherry, citrus,Clementine, coffee, com, cotton, cucumber, eggplant, endive, eucalyptus, figs, grape, grapefruit, groundnuts, ground cherry, kiwifruit, lettuce, leek, lemon, lime, pine, maize, mango, melon, millet, mushroom, nut oat, okra, onion, orange, an ornamental plant or flower or tree, papaya, parsley, pea, peach, peanut, peat, pepper, persimmon, pineapple, plantain, plum, pomegranate, potato, pumpkin, radicchio, radish, rapeseed, raspberry, rice, rye, sorghum, soy, soybean, spinach, strawberry, sugar beet, sugarcane, sunflower, sweet potato, tangerine, tea, tobacco, tomato, a vine, watermelon, wheat, yams and zucchini, or a part thereof.

12. The method of claim 1, wherein the days to a desired maturity of said plant is reduced at least 60% when compared to a control plant grown in full sun for at least an eight-hour photoperiod.

13. A method of accelerating harvest of a plant, comprising:an enclosed growth chamber having:at least one rack for holding one or more plants or plant parts potted in one or more containers;one or more light emitting diode (LED) lights situated above the one or more containers containing the plants, wherein the LED lights are contained on a bar or are individually hung above the plants or plant parts; andwhereas the LED lights can be adjusted in a vertical position;allowing the LED lights to remain on continuously for at least an 8 hour photoperiod during each twenty-four hour period; andcontinuously adjusting the LED lights with the height of plant canopy, so that the distance between the LED light and plant canopy is at least 25 centimeters until the one or more plants reach a desired maturity.

14. The method of claim 13, wherein the growth chamber is enclosed with individually or in combination with fabric, glass, metal, or plastic, dry wall or on all sides.

15. The one or more racks of claim 3, wherein said racks are arranged linearly and / or vertically.

16. The method of claim 13, wherein said LED lights comprise at least 30 watts of power and at least 2700 lumens of luminous flux.

17. The method of claim 13, wherein the LED light has a continuous intensity of at least 600 pmol m-2 s-1.

18. The method of claim 13, wherein the LED light has a continuous intensity of at least 700 pmol m-2 s-1.

19. The method of claim 13, wherein the LED light has a continuous intensity of at least 800 pmol m-2 s-1.

20. The method of claim 13, wherein the LED light has a continuous intensity of at least 900 pmol m-2 s-1.

21. The method of claim 13, wherein the LED light has a continuous intensity of at least 1,00 pmol m-2 s-1.

22. The fabric of claim 14, wherein the fabric consists of a double layer of non-woven fabric.

23. The method of claim 1, wherein said plant is alfalfa, apple, apricot, artichoke, asparagus, avocado, banana, barley, beans, beet, blackberry, blueberry, Brassica, broccoli, brussel sprouts, cabbage, canola, carrot, cassava, cauliflower, a cereal, celery, cherry, citrus, Clementine, coffee, com, cotton, cucumber, eggplant, endive, eucalyptus, figs, grape, grapefruit, groundnuts, ground cherry, kiwifruit, lettuce, leek, lemon, lime, pine, maize, mango, melon, millet, mushroom, nut oat, okra, onion, orange, an ornamental plant or flower or tree, papaya, parsley, pea, peach, peanut, pepper, persimmon, pineapple, plantain, plum, pomegranate, potato, pumpkin, radicchio, radish, rapeseed, raspberry, rice, rye, sorghum, soy, soybean, spinach, strawberry, sugar beet, sugarcane, sunflower, sweet potato, tangerine, tea, tobacco, tomato, a vine, watermelon, wheat, yams and zucchini, or a part thereof.

24. The method of claim 13, wherein the days to maturity of said plant is reduced at least 60% when compared to a control plant grown in full sun for at least an eight-hour photoperiod.

25. An immature or mature plant seed produced by the method of claim 1.

26. The method of claim 1, wherein said plant flowers at least 10, 11, 12, 13, 14, 15 and 16 earlier than a control plant not produced by the method.

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