A method for shortening the breeding cycle of corn

Abstract

The present application provides a method for shortening the breeding cycle of corn, which promotes early maturity of seeds by using suitable photoperiod in the stages of sowing-germination, germination-elongation, elongation-tasseling, artificial pollination-harvesting, and using drought treatment in the stage of artificial pollination-harvesting. The method of the present application significantly shortens the growth cycle of corn and can significantly accelerate the corn breeding process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of agricultural breeding and propagation technology. Specifically, the present application provides a method for shortening the propagation cycle of maize. BACKGROUND

[0002] In modern agricultural production, maize is one of the leading food crops in China, and its variety improvement and optimization are crucial for national food security and sustainable agricultural development. However, the limitations of traditional breeding techniques, such as long breeding cycles, have increasingly become a bottleneck restricting the development of China's maize industry. Under normal circumstances, maize from sowing to the harvest stage takes about 4 to 6 months, and only 1 to 2 generations can be implemented in a year. Even using the method of southward propagation, at most 3 generations can be achieved in a year. Therefore, it usually takes more than ten years to select an excellent new maize variety, which not only requires huge human and material resources, but also the cultivated varieties often cannot meet the real-time needs of the market and production. Under this background, improving breeding speed, shortening breeding time, and enhancing breeding efficiency have become the key issues of hybrid breeding technology innovation, which has a profound impact on scientific research and practical application.

[0003] In recent years, the rapid development and maturation of plant factory technology have provided new opportunities for accelerating the growth and development cycle of crops. Through the integrated application of environmental control technology, an ideal growth environment is created (involving light, temperature, humidity, carbon dioxide concentration, and nutrient supply, etc.), combined with timely harvesting and germination treatment of not fully mature seeds, which can significantly reduce the overall cycle of plants from growth to maturity, thereby effectively improving the efficiency and speed of breeding and accelerating the breeding process. SUMMARY

[0004] In one aspect, the present application provides a method for shortening the propagation cycle of maize, the method comprising the following steps:

[0005] (1) Sowing-germination: 13-15 hours of light per day, preferably 14 hours; temperature 27-35℃, preferably daytime temperature 30-33℃, nighttime temperature 27-30℃, daily average temperature 30-31℃; humidity 60% to 90%;

[0006] (2) Emergence-elongation: 13-15 hours of light per day, preferably 14 hours; temperature 24-32℃, preferably daytime temperature 28-32℃, nighttime temperature 24-28℃, daily average temperature 28-29℃; humidity 60% to 90%;

[0007] (3) Elongation - Duster: 11-13 hours of light per day; preferably 12 hours; temperature of 23-31 °C, preferably a daytime temperature of 27-31 °C, a nighttime temperature of 23-27 °C, and a daily average temperature of 27-28 °C; humidity of 60% to 90%;

[0008] (4) Artificial pollination - Harvest: 13-15 hours of light per day, preferably 14 hours; stop watering 8-12 days after pollination for drought treatment; temperature of 22-30 °C, preferably a daytime temperature of 26-30 °C, a nighttime temperature of 22-26 °C, and a daily average temperature of 26-27 °C; humidity of 50% to 70%;

[0009] (5) Harvest seeds 18-22 days after pollination, inbred Z58 22 days after pollination, inbreds ND101 and FFMM 20 days after pollination, super-early-mature No. 1 18 days after pollination.

[0010] (6) Dry the harvested seeds by drying at a temperature of 35-40 °C for 3 days to end the dormancy period for storage.

[0011] Further, the light quality ratio of red: green: blue used in the method is 5.5-7.0: 1.5-2.0: 1.0; the light intensity at 20-100 cm under the light is 300 to 1800 μmol / m 2 / s.

[0012] Further, the light quality ratio used in the method is 400-499 nm: 11-12%, 500-599 nm: 18-20%, and 600-699 nm: 68-70%; the light intensity at 100 cm under the light is 300 μmol / m 2 / s.

[0013] The light uses an LED light supplement, as an example, the light efficiency of the light supplement is more than 3.0 μmol / J, and the light uniformity (the ratio of the minimum light intensity to the average light intensity) at 1 meter under the light is better than 0.68.

[0014] Further, the corn variety is selected from Zheng 58, ND101, FFMM, and super-early-mature No. 1.

[0015] Further, when the corn variety is ND101 or Zheng 58, the watering is stopped 10-12 days after pollination for drought treatment in step (4); when the corn variety is FFMM or super-early-mature No. 1, the watering is stopped 8 days after pollination for drought treatment in step (4).

[0016] Further, the method uses soilless culture; preferably, the soilless culture is substrate hydroponics; more preferably, in the substrate hydroponics, the corn seeds are sown in flowerpots with a height of 18 cm and a radius of 9 cm, the substrate in the flowerpots is filled to a height of 16 cm, and then the flowerpots are placed in a planting tank, and the nutrient solution in the tank is kept at a depth of 1-3 cm.

[0017] Further, the culture substrate in the method is a mixture of grass charcoal, perlite and vermiculite in a volume ratio of 5:1:1; preferably, the culture substrate is prepared as follows: grass charcoal, perlite and vermiculite are mixed in a volume ratio of 5:1:1 to obtain a substrate mixture; 5 L of chicken manure organic fertilizer, 10 g of calcium hydroxide, 50 g of potassium sulfate compound fertilizer and 50 g of diammonium phosphate are added to every 100 L of the substrate mixture and mixed uniformly, 3 L of the substrate is filled in a 4 L flowerpot, and 1 L of water is poured for standby.

[0018] The method of the application can be carried out in an artificial climate chamber equipped with a light supplementing system, a temperature control system, a humidity control system and an automatic irrigation control system, so that the light and environmental parameters (such as the liquid level in the planting tank) can be completely controlled and have repeatability.

[0019] In the application, the air humidity is maintained at 60-90% during sowing to the powdery stage, and the humidity is controlled at 50-70% from the powdery stage to the harvest stage to prevent ear rot.

[0020] In another aspect, the application provides the use of the above method in corn breeding, corn production, germplasm resource protection / preservation and corn-related scientific research.

[0021] The application greatly improves the speed of crop intergenerational cycle by optimizing the light quality ratio, photoperiod, light intensity and using the most suitable growth temperature and seed early maturity technology. This method significantly shortens the growth period of corn, enabling 5-7 generations of breeding within a year, thereby greatly reducing the time cost of the breeding process and significantly improving the breeding efficiency.

[0022] Further, the application breaks through the constraints of traditional breeding and cultivation techniques and successfully achieves a significant reduction in the growth period of corn. Using the year-round uninterrupted corn production system in the plant factory, this technological innovation not only effectively solves the long cycle and low efficiency problem that has plagued corn breeding research and development for a long time, but also promotes the deep integration of modern seed industry and artificial intelligence technology. The integration of this technology promotes the formation of a new economic industry system of "intelligent + seed industry", opening up a new road for the development of agricultural technology and industrial revolution. DETAILED DESCRIPTION

[0023] The following examples facilitate a better understanding of the present application, but are not limited thereto, and are only for illustrative purposes, which in no way limit the scope of protection of the present application.

[0024] Example 1

[0025] In this example, corn inbred line Zheng 58 (Z58) was used as the test material to optimize the light supplement period.

[0026] (1) Prepare the substrate: mix turf, perlite and vermiculite in a volume ratio of 5:1:1, and add chicken manure organic fertilizer 5L (containing pure nitrogen, phosphorus (P205) and potassium (K20) about 1.63%, 1.54% and 0.85%), calcium hydroxide 10g (effective ingredient content 99%), potassium sulfate compound fertilizer 50g (effective ingredient content 45%) and diammonium phosphate 50g (effective ingredient content 64%) per 100 liters of substrate and mix well, fill 3L substrate in a 4L flowerpot, and pour 1L water for standby.

[0027] (2) Sowing-seeding period

[0028] Select corn seeds with complete appearance and undamaged epidermis, sow in the center of the prepared flowerpot, and sow at a depth of 2-3 cm, and spray with 100ml nutrient solution after covering the soil to ensure that the seeds are in contact with water and substrate. In this example, 60 seeds were sown. After sowing, the specific time of sowing was recorded in detail. Set the artificial climate room growth environment: daytime temperature 30-33℃, nighttime temperature 27-30℃, and humidity 60%-90%.

[0029] (3) Germination-pollination period

[0030] After the corn seeds germinated, 48 strains were selected and divided into 4 groups, and they were moved to the corresponding planting tank equipped with LED light supplement lamp for continuous growth. The light supplement period was set to 4 groups, 10 hours / day (10h / d), 12 hours / day (12h / d), 14 hours / day (14h / d) and 16 hours / day (16h / d). The indoor temperature during the day was maintained at 27-31℃, and at night it was maintained at 23-27℃, and the humidity was controlled between 60-90%.

[0031] The power of the light supplement lamp is 300W, the light efficiency is 3.0μmol / J, the average light intensity under the lamp is >300μmol / m 2 / s, the proportion of 400-499nm photons is 11-12%, the proportion of 500-599nm photons is 18-20%, and the proportion of 600-699nm photons is 68-70%, which can meet the different needs of corn at different growth stages.

[0032] The plants were observed twice daily and the time of each leaf unrolling was recorded in detail to closely monitor the growth progress and health status of the plants.

[0033] (4) Pollination - Harvest

[0034] After the artificial pollination was completed, the 12-hour / day treatment material (12 plants) was divided into 3 groups, each with a light supplement period of 12 hours / day, 14 hours / day and 16 hours / day. The daytime temperature was maintained at 26-30°C and the nighttime temperature was maintained at 22-26°C, and the humidity was controlled between 50% and 70%, which was conducive to the rapid growth and maturation of the grains. The ears were harvested 22 days after pollination, and the fresh weight of the ears was recorded.

[0035] Table 1 Leaf unrolling time and time required for pollination under different light periods

[0036]

[0037]

[0038] The results in Table 1 show that when the light period is set to 10 hours or 12 hours per day in the light period management of the culture system, the time required for the plants to reach the pollination period is the shortest, only 45 days. In contrast, when the light period is increased to 16 hours per day, the time required is the longest, 62 days, and the number of leaves of the plants can reach 23 at this time. As the light period is extended, the growth state of the plants also tends to be robust. In addition, whether the light is supplemented for 10 hours, 12 hours or 14 hours, the time for the plants to reach the jointing stage is roughly equivalent. In summary, the recommended light supplement strategy is: during the germination to jointing stage, the light period is 14 hours per day. During the jointing to tasseling stage, the light period is 12 hours per day.

[0039] Table 2 Ear weight and grain number of corn under different light periods

[0040] 16h / d 14h / d 12h / d Ear fresh weight (g) 109 106 83 Ear grain number (grain) 287 293 270

[0041] The results in Table 2 show that after pollination is completed, if the light period is adjusted to 14 hours or 16 hours per day, the fresh weight of the corn ears can exceed 100 grams. In contrast, if the light period is maintained at 12 hours per day, the weight of the corn ears is relatively light, only more than 80 grams. Considering energy saving and efficiency, we recommend that after the corn completes pollination, the light period should be set to 14 hours per day to achieve the best growth effect.

[0042] Example 2

[0043] In this example, corn inbred line ND101 was used as the test material to optimize the drought treatment time.

[0044] (1) Preparation of the substrate: mix the turf, perlite and vermiculite in a volume ratio of 5:1:1, and then add chicken manure organic fertilizer 5L (containing pure nitrogen, phosphorus (P2O5), potassium (K2O) about 1.63%, 1.54%, 0.85%), calcium hydroxide 10g (effective ingredient content is 99%), potassium sulfate compound fertilizer 50g (effective ingredient content is 45%) and diammonium phosphate 50g (effective ingredient content is 64%) per 100 liters of substrate and mix well, fill 3L of substrate in a 4L flowerpot, and pour 1L of water for standby.

[0045] (2) Sowing and germination period

[0046] Select corn seeds with complete appearance and undamaged epidermis, sow in the center of the prepared flowerpot, with a sowing depth of 2-3 cm, and spray with 100ml of nutrient solution after covering the soil to ensure that the seeds are in full contact with water and substrate. A total of 40 ND101 seeds were sown in this example. After sowing, the specific sowing time was recorded in detail. The artificial climate chamber growth environment was set as follows: daytime temperature 30-33℃, nighttime temperature 27-30℃, and humidity maintained at 60%-90%, while providing 14 hours of supplemental light per day. When the seedlings emerged about 2 cm, the emergence time was recorded and the germination rate was calculated.

[0047] (3) Germination and jointing period

[0048] After the corn seeds germinated, they were moved to a planting tank equipped with LED supplemental light to continue growing. The top of the seedlings was kept 30 cm away from the supplemental light, and the distance between the plants and the lamps was adjusted in time according to the change in plant height, maintaining a distance of 10 to 30 cm to achieve the best lighting effect.

[0049] The power of the supplemental light is 300W, the light efficiency is 3.0μmol / J, the average light intensity under the lamp is >300μmol / m2 / s, the proportion of 400-499nm photons is 11-12%, the proportion of 500-599nm photons is 18-20%, and the proportion of 600-699nm photons is 68-70%, which can meet the different needs of corn at different growth stages.

[0050] The supplemental light was set to automatically turn on at 5:00 and turn off at 19:00 every day, with 14 hours of supplemental light per day, and the relative humidity was set between 60-90% to create a suitable humid growing environment. Observe in the morning and evening every day, and record the time of each leaf unfolding in detail to closely monitor the growth progress and health status of the plants.

[0051] (4) Jointing and tasseling period

[0052] At this critical stage, the corn plants grow rapidly and enter a stage focused on reproductive growth. To cope with the sensitivity of corn to photoperiod at this stage, the light period is shortened. Each day, the light is supplemented for 12 hours (6:00-18:00), with daytime temperatures maintained at 27-31°C and nighttime temperatures maintained at 23-27°C, with humidity controlled between 60-90%. At the same time, the relative positions of the plants are adjusted to prevent mutual shading of the leaves, thereby ensuring that each corn plant receives uniform light.

[0053] (5) Artificial pollination

[0054] Artificial pollination is performed using artificial assistance. When the female ear is about 3 cm long, it is bagged to prevent silk running. When the male ear begins to shed pollen, it is bagged, and the female ear silk is trimmed. Pollination begins the next morning at around 9:00, after which the male ear is removed, and the pollination time is recorded.

[0055] (6) Pollination-harvesting

[0056] After pollination is complete, the light supplement is set to work for 14 hours per day (5:00-19:00), with daytime temperatures maintained at 26-30°C and nighttime temperatures maintained at 22-26°C, with humidity controlled between 50-70%. The experimental materials are divided into five groups for different treatments. Treatment 1 stops water supply on the 8th day after pollination to simulate drought conditions; treatment 2 stops water supply on the 10th day; treatment 3 stops water supply on the 12th day; treatment 4 continues to the 14th day before stopping water supply; and treatment 5 maintains normal water supply throughout the process. All treatment groups are harvested 20 days after pollination.

[0057] All corn seeds of the treatments are subjected to a 3-day drying process to break dormancy. Subsequently, germination rate tests are conducted (10 seeds per treatment), with the following results:

[0058] Table 3 Effect of different drought treatments on seed germination rate

[0059] Treatment 1 Treatment 2 Treatment 3 Treatment 4 Treatment 5 Emergence rate 70％ 90％ 60％ 50％ 30％

[0060] Table 3 shows the significant effect of different treatments on seed germination rate. In particular, treatment 2, which began drought treatment on the 10th day after pollination, had the highest seed germination rate, reaching 90%. In contrast, treatment 1, which had an early drought treatment duration, was not conducive to organic matter accumulation. Treatments 3 and 4 showed that delaying drought treatment would weaken the effect of promoting early seed maturation. Therefore, based on the comprehensive analysis of the results, the recommended drought strategy is to start drought treatment on the 10th day after pollination for ND101 to effectively promote early seed maturation.

[0061] Example 3

[0062] Four corn inbred lines were used as test materials in this example.

[0063] The four corn inbred lines are as follows:

[0064] 1) Zheng 58 (Z58)

[0065] 2) ND101

[0066] 3) FFMM (Fast-Flowering Mini-Maize)

[0067] 4) Super Early 1

[0068] (1) Prepare the substrate: mix charcoal soil, perlite, and vermiculite in a volume ratio of 5:1:1. Add chicken manure organic fertilizer 5L (containing pure nitrogen, phosphorus (P2O5), and potassium (K2O) about 1.63%, 1.54%, and 0.85%), calcium hydroxide 10g (effective ingredient content is 99%), potassium sulfate compound fertilizer 50g (effective ingredient content is 45%), and diammonium phosphate 50g (effective ingredient content is 64%) per 100 liters of substrate and mix well. Fill 3L of substrate in a 4L flowerpot and water 1L for standby.

[0069] (2) Sowing and germination period

[0070] Select corn seeds with complete appearance and undamaged skin, sow in the center of the prepared flowerpot, with a sowing depth of 2-3cm, and spray with 100ml of nutrient solution after covering the soil to ensure that the seeds are in full contact with water and substrate. In this example, four different materials were sown, namely ND101, Z58, FFMM, and Super Early 1, with 10 seeds of each material sown. After sowing, the specific sowing time was recorded in detail. Set the artificial climate room growth environment: daytime temperature 30-33℃, nighttime temperature 27-30℃, and humidity 60%-90%, while providing 14 hours of light per day. When the seedlings emerged about 2cm, record the emergence time and calculate the germination rate.

[0071] (3) Germination and jointing period

[0072] After the corn seeds germinated, they were moved to a planting tank equipped with LED supplemental lighting for further growth. The nutrient solution depth in the planting tank was managed by a precise liquid level control valve, which automatically replenished when the liquid level was below 1cm and stopped adding liquid when it reached 3cm, ensuring a constant supply of nutrients to the plant roots. The top of the seedlings was kept 30cm away from the supplemental lighting, and the distance was adjusted according to the plant growth height.

[0073] The power of the light supplement lamp is 300W, the light efficiency is 3.0 μmol / J, the average light intensity under the lamp is > 300 μmol / m2 / s, the proportion of 400-499 nm photons is 11-12%, the proportion of 500-599 nm photons is 18-20%, and the proportion of 600-699 nm photons is 68-70%, which can meet the different needs of corn for light at different growth stages.

[0074] The light supplement lamp is set to automatically turn on at 5:00 and turn off at 19:00 every day, and the light supplement is 14 hours. At the same time, the relative humidity of the environment is set to 60-90% to create a suitable humid growing environment. Each day, the time of each leaf unfolding is recorded in detail to closely monitor the growth progress and health status of the plants.

[0075] (4) Jointing stage - tasseling stage

[0076] At this critical period, the corn plants grow rapidly and enter a stage focusing on reproductive growth. The depth of the nutrient solution in the planting tank continues to be accurately maintained through the automatic liquid level control valve, ensuring that the plant's root system can effectively absorb the necessary water and nutrients. As the plants gradually grow, adjust their distance from the LED light supplement lamp in a timely manner, keeping the distance between 10 and 30 centimeters to achieve the best lighting effect. At the same time, adjust the relative position of the plants to prevent leaf shading, ensuring that each corn plant receives uniform light.

[0077] In order to cope with the sensitivity of corn to light period at this stage, we shorten the light period to promote the plant to enter the tasseling stage as soon as possible. Each day, the light supplement is 12 hours (6:00-18:00), the daytime temperature is maintained at 27-31℃, the nighttime temperature is maintained at 23-27℃, and the humidity is controlled between 60-90%.

[0078] (5) Artificial pollination

[0079] Artificial pollination is adopted. When the female ear is about 3 cm long, it is bagged to prevent silk running. When the male ear starts to shed pollen, it is bagged, and the female ear silk is trimmed. The next morning at about 9 o'clock, pollination begins, then the male ear is removed, and the pollination time is recorded.

[0080] (6) Pollination - harvest

[0081] After pollination, the light supplement was set to 14 hours per day (5:00-19:00), the temperature was maintained at 26-30°C during the day and 22-26°C at night, and the humidity was controlled between 50% and 70%. These conditions were conducive to the rapid growth and maturation of the seeds. Nutrient solution was stopped 8-12 days after pollination to induce drought stress, which promoted early seed maturation. The duration of drought stress varied depending on the characteristics of the different varieties. FFMM and Super Early 1 were subjected to drought stress about 8 days after pollination, while Z58 and ND101 were subjected to drought stress 10-12 days after pollination. Inbred Zheng58 was harvested 22 days after pollination, inbred ND101 and FFMM were harvested 20 days after pollination, and Super Early 1 was harvested 18 days after pollination.

[0082] The corn seeds then needed to be dried and the dormancy broken. Air heat pump technology was used for drying, and the drying temperature was adjusted to between 35°C and 40°C for 3 days to end the dormancy period and make them ready for use.

[0083] Measurement indicators and methods

[0084] 1) Growth stage statistics

[0085] The number of days required to reach different leaf stages during the period from corn planting to harvesting was recorded.

[0086] The definition of corn leaf fully expanded is that the leaves of the corn plant have fully stretched out of the leaf sheath and no longer continue to grow or lengthen. One fully expanded leaf is considered as one leaf stage.

[0087] Table 4 Number of days required for different materials to complete a growth cycle

[0088]

[0089]

[0090] FFMM only required 53 days to complete a complete growth cycle, allowing for 7 generations to be continuously bred within a year. Super Early 1 required 59 days to complete a complete growth cycle, allowing for at most 6.2 generations to be continuously bred within a year. In comparison, inbred Zheng58 and inbred ND101 required 70 days and 73 days, respectively, to complete a growth cycle, and still allowed for a breeding frequency of more than 5.0 generations per year.

[0091] Finally, it should be noted that the above-described embodiments are merely used to illustrate the technical solutions of the present application, instead of limiting the present application; even though the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions recorded in the foregoing embodiments, or one or more or all of the technical features therein can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for shortening the maize breeding cycle, characterized in that, The corn variety is selected from Zheng 58, ND101, FFMM, or Super Early Maturity No. 1, and the method includes the following steps: (1) Sowing-germination: 14 hours of light per day; daytime temperature 30-33℃, nighttime temperature 27-30℃, average daily temperature 30-31℃; humidity 60% to 90%; (2) Bud emergence-jointing: 14 hours of light per day; daytime temperature 28-32℃, nighttime temperature 24-28℃, average daily temperature 28-29℃; humidity 60% to 90%; (3) Jointing-Powdering: 12 hours of light per day; daytime temperature 27-31℃, nighttime temperature 23-27℃, average daily temperature 27-28℃; humidity 60% to 90%; (4) Artificial pollination-harvest: 14 hours of sunlight per day; stop watering 8-12 days after pollination and carry out drought treatment; daytime temperature 26-30℃, nighttime temperature 22-26℃, average daily temperature 26-27℃; humidity 50% to 70%. (5) Harvest seeds 18-22 days after pollination. Harvest the inbred line Zheng 58 22 days after pollination, the inbred line ND101 or FFMM 20 days after pollination, and the super early maturing No. 1 18 days after pollination. (6) The harvested seeds are dried at a temperature of 35℃-40℃ for 3 days to end their dormancy period and prepare them for use. The light source used in the method has the following light quality ratios: 400-499nm: 11-12%, 500-599nm: 18-20%, 600-699nm: 68-70%; the light intensity at 100cm under the lamp is 300μmol / m². 2 / s; The method described uses a substrate hydroponics method for propagation.

2. According to the method of claim 1, when the corn variety is ND101 or Zheng58, water supply is stopped 10-12 days after pollination in step (4) and drought treatment is carried out; when the corn variety is FFMM or Super Early Maturity No. 1, water supply is stopped 8 days after pollination in step (4) and drought treatment is carried out.

3. According to the method of claim 1, in the substrate hydroponics method, corn seeds are sown in flowerpots with a height of 18cm and a radius of 9cm, the culture medium filling the flowerpots is filled to a height of 16cm, and then these flowerpots are placed in planting troughs, keeping the nutrient solution depth in the troughs between 1 and 3cm.

4. According to the method of claim 3, the culture medium is prepared by the following method: peat moss, perlite and vermiculite are mixed evenly in a volume ratio of 5:1:1 to obtain a substrate mixture; 5L of chicken manure organic fertilizer, 10g of calcium hydroxide, 50g of potassium sulfate compound fertilizer and 50g of diammonium phosphate are added to every 100L of substrate mixture and mixed evenly, 3L of substrate is filled into a 4L flower pot, and 1L of water is added for later use.

5. The method according to any one of claims 1-4, wherein the method is performed in an artificial climate chamber.

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