Breeding method of pre-harvest sprouting resistant rice

Abstract

The invention discloses a breeding method of pre-harvest sprouting-resistant rice, which comprises the following steps of: hybridizing a pre-harvest sprouting-resistant germplasm resource serving as a female parent and a variety which is large in popularization area and has popularization potential in current production and serves as a male parent to construct a hybrid combination F1; carrying out preliminary screening on progeny materials of preharvest-resistant sprouting germplasm resources, and carrying out field seed selection in the F2 population after water spraying treatment; f3-F5 generations and generation adding are stable, and the growth period is classified; and in a temperature-controllable multi-span greenhouse, simulating plum rain weather through an unmanned aerial vehicle, and performing large-scale and high-repeatability pre-harvest sprouting resistance final identification on the stable strain. And finally screening resistant strains by taking the ear germination rate lower than that of the same-period contrast as a standard. According to the method, the uncontrollable pre-harvest sprouting identification environment is changed into the controllable pre-harvest sprouting identification environment, the technical problems that an existing method is poor in repeatability and disjointed with the actual situation are solved, the method has the advantages of being accurate in identification result, high in efficiency and good in repeatability, and reliable technical support is provided for efficient breeding of new pre-harvest sprouting resistant rice varieties.

Description

Technical Field

[0001] This invention relates to a method for breeding rice, and more particularly to a method for breeding rice resistant to panicle sprouting. Background Technology

[0002] In recent years, affected by global climate change, rice panicle sprouting has become increasingly serious. Sprouting not only significantly reduces rice yield but also leads to deterioration in rice quality, increased amylase activity, and a substantial decrease in processing performance and edible value, becoming a major problem affecting safe rice production.

[0003] Rice panicle germination is mainly influenced by three types of factors: climatic conditions, cultivation management practices, and varietal characteristics. Regarding climatic factors, continuous rainy weather during the rice ripening period creates a hot and humid environment, increasing the moisture content of the rice grains and creating suitable germination conditions. In terms of cultivation management, improper irrigation during the grain-filling stage leading to excessive field humidity, or prolonged soaking of grains in water after lodging, significantly increases the risk of panicle germination. Regarding varietal characteristics, the length of the dormancy period and the thickness of the seed coat are key traits determining resistance to panicle germination; varieties with shorter dormancy periods and thinner seed coats are more prone to panicle germination.

[0004] Currently, there are two main methods for identifying ear germination: field natural identification and grain culture dish germination identification. While field natural identification can accurately reflect field production conditions, it is greatly affected by fluctuations in the natural environment. Different varieties encounter completely different climatic conditions due to differences in their growth stages, leading to poor repeatability and low comparability of experimental results. Although grain culture dish germination identification can control environmental factors, the in vitro culture conditions differ significantly from actual field conditions, making it unable to accurately reflect the resistance performance of varieties in real production environments.

[0005] Therefore, there is an urgent need to establish a method for identifying panicle germination that can simulate the natural field environment and achieve controllable and reproducible conditions, so as to provide an effective technical means for breeding rice varieties resistant to panicle germination. Summary of the Invention

[0006] Purpose of the invention: In order to overcome the defects in the existing technology, the present invention proposes a breeding method for rice resistant to panicle germination with controllable environment and good repeatability, which solves the problems of uncontrollable environment, poor repeatability and disconnect from actual situation in the existing identification methods.

[0007] Technical Solution: To solve the above-mentioned technical problems, the technical solution adopted by this invention is: a method for breeding rice resistant to panicle germination, comprising the following steps:

[0008] (1) Collection and cross-matching of germplasm resources with tolerance to panicle germination: Using rice germplasm resources with tolerance to panicle germination as the female parent and varieties with large current production area and potential for promotion as the male parent, cross-matching is carried out to construct the F1 hybrid combination;

[0009] (2) Preliminary screening of offspring materials of germplasm resources resistant to ear sprouting: Induced by field environment, the F2 population was sprayed with water by drone from the time a single plant was found to have entered the waxy ripening stage to induce ear sprouting.

[0010] (3) In the F2 population after water spraying treatment, select individual plants with good agronomic traits, no obvious tilting, and no ear sprouting. Induce germination of the selected individual plants in a culture box, remove the sprouted seeds, and keep the rest for sowing in the next season.

[0011] (4) F3-F5 generation, stable generation, classified by reproductive period, divided into three categories according to the entire reproductive period: medium-maturing medium japonica, late-maturing medium japonica, and early-maturing late japonica;

[0012] (5) In the F6 generation, the stable strains were subjected to a large-scale, highly repeatable final identification of their germination tolerance by using drones to simulate the plum rain season in a temperature-controlled multi-span greenhouse.

[0013] Furthermore, the rice germplasm resource selected as the maternal parent in step (1) for its resistance to panicle germination is the Japanese japonica rice variety Koshihikari. Koshihikari possesses strong stress resistance and dormancy characteristics, one of its features being high-temperature tolerance. This allows it to better resist panicle germination in hot and rainy environments. In addition, Koshihikari has a thicker seed coat, which also increases its resistance to panicle germination, making it less prone to this phenomenon. Therefore, Koshihikari is a suitable parent for a germplasm resource resistant to panicle germination.

[0014] Furthermore, in step (1), the parent plant selected is the high-quality soft rice variety Zhendao 6243.

[0015] Furthermore, the specific method for inducing ear sprouting by spraying water with drones in step (2) is as follows: starting from the discovery of a single plant entering the waxy ripening stage, the F2 population is treated by watering with agricultural drones. The flight altitude is set at 2.5-3m, and the spraying time is 10 am and 2 pm every day. The spraying cycle continues until all F2 populations enter the waxy ripening stage.

[0016] Furthermore, the specific method for field selection described in step (3) is as follows: In the field, select single plants that have not tilted significantly, have not sprouted panicles, and have good agronomic traits. Take two panicles from each selected single plant, number them, and label them. Soak the selected panicles for 20-24 hours, wrap them with a damp cloth, then wrap them with plastic wrap and place them in an incubator. Starting from the second day, take out the selected single plants every 12 hours, soak them for 10-15 minutes, then wrap them with a damp cloth and plastic wrap and place them in an incubator. Continue this process until the sixth day. On the seventh day, take out the selected single plant panicles, dry them, remove any sprouted seeds, and keep the rest for sowing in the next season. Wrapping them with a damp cloth ensures that the panicles are moist but do not accumulate water, and wrapping them with plastic wrap reduces the loss of moisture from the surface of the panicles.

[0017] Furthermore, in step (5), within a temperature-controlled multi-span greenhouse, a large-scale, highly reproducible final identification of the germination tolerance of stable varieties was conducted using a drone to simulate the plum rain season. The specific steps were as follows: The selected rice varieties of the three growth stages were transplanted to three multi-span greenhouses with a height of 2.5-3m. The top and sides of the multi-span greenhouses were equipped with film-rolling devices to control the opening and closing. The control variety was set as Koshihikari, which was sown in three stages to ensure that each variety had a corresponding Koshihikari that entered the waxy ripening stage at the same time. Each variety near the perimeter of the multi-span greenhouse was planted 1.5-2.5m away from the perimeter of the greenhouse. 35-40 days after the rice headed out, the film-rolling device on the top of the multi-span greenhouse was opened, and an agricultural drone was turned on to spray water at a height of 2.5-3m above the multi-span greenhouse. After spraying, the film-rolling device on the top of the multi-span greenhouse was closed. Spraying was carried out at 10:00 AM and 2:00 PM every day for 6 consecutive days. Sampling and screening of germination tolerance varieties were conducted.

[0018] Furthermore, in step (5), when transplanting rice of the three growth stages, each rice variety is divided into 3 replicates, and each replicate is planted with 48 plants, specifically 4 rows with 12 plants per row; the plant spacing is 7.5 inches × 4 inches.

[0019] Furthermore, the parameters for drone-based precipitation are as follows: the water volume is set to 150-200L per mu, and 5-10mg of gibberellin is added per liter of water to break the dormancy of rice seeds and promote germination of panicles; the flight speed is set to 3-5m / s.

[0020] Furthermore, the temperature control method in the connected greenhouses is as follows: Eight minimum and maximum thermometers are evenly distributed in each connected greenhouse to monitor the temperature uniformity and diurnal temperature variations, controlling the daytime greenhouse temperature between 28 and 32°C. Within this temperature range, enzyme activity is higher, which is beneficial to the physiological and biochemical reactions within the seeds, thereby promoting germination. When the temperature exceeds 35°C, the film-rolling device is opened and water is poured in to cool it down; when the temperature is below 25°C, the film-rolling device is closed to maintain warmth; at night, all film-rolling devices are closed.

[0021] Furthermore, the specific method for sampling and screening resistant spikelet germination lines is as follows: Select lines that have not tilted, take 3 replicates for each line, and take 5 consecutive plants starting from the third plant in the second row for each replicate; bring them back to the laboratory to investigate spikelet germination, and compare spikelet germination with that of Koshihikari, which also enters the waxy ripening stage at the same time. Those with a germination rate lower than Koshihikari are retained, and those with a higher germination rate are eliminated.

[0022] Beneficial effects:

[0023] The present invention provides a method for breeding rice resistant to panicle germination, which has the following advantages:

[0024] 1) Close to production, it can truly reflect the panicle sprouting situation of different varieties in the field: The agricultural drone rainfall simulates the plum rain weather encountered by rice varieties before and after harvest. The experimental height is close to the high temperature and high humidity weather encountered by rice during the ripening period, which can truly reflect the panicle sprouting caused by weather factors.

[0025] 2) Environmental factors (temperature, humidity, precipitation, etc.) are controllable and have good repeatability: Each rice variety is sprayed with water evenly by drone, and the precipitation per unit area is consistent and controllable. After spraying, the greenhouse is closed with the top film rolling device, which not only keeps the temperature and improves the conditions for inducing panicle germination, but also keeps all varieties in a closed space with a constant temperature (the greenhouse is equipped with minimum and maximum thermometers to ensure that the temperature in local areas is within the monitoring range). The uniform precipitation and constant temperature ensure that the humidity of different varieties is the same, and each variety is set with 3 replicates to ensure the repeatability of the experiment.

[0026] 3) Enhanced screening for lodging resistance and germination tolerance: After rice lodging, the rice seeds remain submerged in water for an extended period, which can promote germination on the panicles. By using drones flying at low altitudes and utilizing the strong winds generated by the rotating propellers, varieties prone to lodging can be eliminated, and varieties with good lodging resistance and germination tolerance can be selected. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of planting in a multi-span greenhouse in Embodiment 1 of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the embodiments:

[0029] Example 1:

[0030] A) Implementation method:

[0031] Please see Figure 1 This invention discloses a method for breeding rice resistant to panicle germination, comprising the following steps:

[0032] 1) Collection of germplasm resources resistant to panicle germination: The Japanese japonica rice variety Koshihikari has strong stress resistance and dormancy characteristics, one of its features being high temperature tolerance. This allows it to better resist panicle germination in hot and rainy environments. In addition, Koshihikari has a thicker seed coat, which also increases its resistance to panicle germination, making it less prone to this phenomenon. Therefore, Koshihikari is a suitable parent for germplasm resources resistant to panicle germination.

[0033] (2) Hybridization of germplasm resources resistant to ear-germination: Hybridization combinations of germplasm resources resistant to ear-germination were constructed using existing germplasm resources resistant to ear-germination. The F1 hybrid combination was constructed using Yueguang as the female parent and the high-quality soft rice Zhendao 6243 as the male parent.

[0034] (3) Preliminary screening of offspring materials of germplasm resources resistant to panicle germination: Through field environment induction, starting from the discovery of individual plants entering the waxy maturity stage in the F2 population, water treatment was carried out using agricultural drones. The spray volume was set at 150-200L per mu (8mg gibberellin was added per liter of water to break the dormancy of rice seeds and promote panicle germination), the flight speed was set at 3-5m / s, the flight height was set at 2.5-3m, and the spraying time was 10:00 am and 2:00 pm every day. The spraying cycle continued until all F2 plants entered the waxy maturity stage. In the field, single plants without obvious tilting, without panicle germination, and with good agronomic traits were selected. Two panicles were taken from each selected single plant, numbered, and tagged. The selected rice panicles were soaked for 20-24 hours, wrapped with a damp cloth, and then wrapped with plastic wrap and placed in an incubator. Starting from the second day, the selected single plants were taken out every 12 hours, soaked for 10 minutes, wrapped with a damp cloth and plastic wrap, and placed in an incubator. This process continued until the sixth day. On the seventh day, the selected single rice ears are taken out, dried in the sun, and the sprouted seeds are removed. The remaining ears are kept for sowing in the next season.

[0035] (4) F3-F5 generation, with stable generation, classified by reproductive period, divided into three categories according to the entire reproductive period: medium-maturing medium-japonica, late-maturing medium-japonica, and early-maturing late-japonica.

[0036] (5) For the F6 generation, the selected rice varieties of the three growth stages were transplanted to three connected greenhouses (each connected greenhouse is approximately 1 mu in area). The greenhouses have openable and closable film-rolling devices on the top and sides. Each rice variety was divided into 3 replicates, with 48 plants (4 rows, 12 plants per row) planted in each replicate, with a plant spacing of 7.5 inches * 4 inches. The control variety was set as Koshihikari, which was sown in 3 phases to ensure that each variety had a corresponding Koshihikari that entered the waxy maturity stage at the same time. Each variety near the perimeter of the connected greenhouse was planted 2 meters away from the perimeter of the greenhouse. 35-40 days after the rice headed out, the film-rolling device on the top of the connected greenhouse was opened, and an agricultural drone was turned on for watering. The water volume was set to 150-200L per mu (8mg gibberellin was added per liter of water to break the dormancy of rice seeds and promote panicle germination), the flight speed was set to 3-5m / s, and the flight height was set to 2.5-3m. After the watering was completed, the film-rolling device on the top of the connected greenhouse was closed. Spraying was conducted daily at 10:00 AM and 2:00 PM for six consecutive days. Eight minimum and maximum thermometers were evenly distributed across each connected greenhouse to monitor temperature uniformity and diurnal temperature variations, aiming to maintain daytime greenhouse temperatures between 28 and 32°C. Within this temperature range, enzyme activity is higher, which is beneficial for the physiological and biochemical reactions within the seeds, thus promoting germination. If the temperature exceeded 35°C, the film-rolling device was opened and water was applied to cool the seedlings; if the temperature fell below 25°C, the film-rolling device was closed for insulation (if conditions permit, a high-powered air conditioner can be installed for temperature control). All film-rolling devices were closed at night. Sampling survey: Strains without tilting were selected, and three replicates were taken from each strain. For each replicate, five plants were sampled consecutively, starting from the third plant in the second row. The germination rate of the panicles was investigated in the laboratory. The germination rate was compared with that of the *Vichy* variety, which entered the waxy ripening stage at the same time. Plants with a germination rate close to or lower than *Vichy* were retained, while those significantly higher were discarded.

[0037] An investigation of the control variety Koshihikari at different sowing dates revealed that the panicle germination rate was less than 5%. Therefore, a panicle germination rate of less than 5% was tentatively defined as a germination-tolerant line, while lines with a panicle germination rate higher than 5% were eliminated. An investigation of the average panicle germination rate (%) of rice lines at three different growth stages revealed 8, 8, and 6 germination-tolerant lines among 126 medium-maturing japonica rice varieties, 168 late-maturing japonica rice varieties, and 158 early-maturing late-maturing japonica rice varieties, respectively.

[0038] B) Comparative experiment:

[0039] (I) Comparison of germination rates between Koshihikari variety and selected strain

[0040] Please refer to the identification results in Table 1. The final identification results show that the germination rate of the control variety Koshihikari during the third sowing in three connected greenhouses was stable between 2.5% and 4.7%, with an average of 3.6%.

[0041] Table 1. Comparison of germination rates between Koshihikari variety and selected strains.

[0042]

[0043]

[0044] As shown in Table 1, in this embodiment, 22 varietals with excellent ear germination tolerance were successfully screened from 452 test strains, with an ear germination rate between 1.6% and 3.4%, significantly lower than the control strain at the same time point. The remaining strains had ear germination rates between 5.2% and 31.3% and were effectively eliminated. This indicates that the method of the present invention can efficiently and accurately identify individuals with excellent ear germination tolerance from a large population.

[0045] (II) Comparative Experiment of Field Natural Identification Method and Seed Germination Identification in Petri Dishes:

[0046] To compare the effects of this invention, a portion of the F6 generation materials (n=50) were simultaneously subjected to field natural induction and grain culture dish germination identification. Field natural induction was subject to varying weather conditions and different materials encountered different conditions, resulting in poor reproducibility (the germination rate of the same line varied by up to 21.2% among different replicates); although grain culture dish germination identification showed good reproducibility, the overall germination rate was too high, making it impossible to distinguish between resistant and moderately resistant materials.

[0047] The 22 highly resistant strains identified by the breeding method of this invention showed excellent repeatability and accuracy, with germination rates differing by less than 5% in three repeated experiments.

Claims

1. A method for breeding rice resistant to panicle germination, characterized in that... Includes the following steps: (1) Collection and cross-matching of germplasm resources with tolerance to panicle germination: Using rice germplasm resources with tolerance to panicle germination as the female parent and varieties with large current production area and potential for promotion as the male parent, cross-matching is carried out to construct the F1 hybrid combination; (2) Preliminary screening of offspring materials of germplasm resources resistant to ear sprouting: Induced by field environment, the F2 population was sprayed with water by drone from the time a single plant was found to have entered the waxy ripening stage to induce ear sprouting. (3) Select seeds in the field in the F2 population after water spraying, select individual plants with good agronomic traits and no obvious tilting or ear sprouting, and induce germination of the selected individual plants in the culture box, remove the sprouted seeds, and keep the rest for sowing in the next season. (4) F3-F5 generation, stable generation, classified by reproductive period, divided into three categories according to the entire reproductive period: medium-maturing medium japonica, late-maturing medium japonica, and early-maturing late japonica; (5) In the F6 generation, the stable strains were subjected to a large-scale, highly repeatable final identification of their germination tolerance by using drones to simulate the plum rain season in a temperature-controlled multi-span greenhouse.

2. The breeding method for rice resistant to panicle germination according to claim 1, characterized in that: The rice germplasm resource with tolerance to panicle germination selected as the maternal parent in step (1) is the Japanese japonica rice variety Koshihikari.

3. The breeding method for rice resistant to panicle germination according to claim 1, characterized in that: The parent plant selected in step (1) is the high-quality soft rice variety Zhendao 6243.

4. The breeding method for rice resistant to panicle germination according to claim 1, characterized in that: The specific method for inducing ear sprouting by spraying water with drones in step (2) is as follows: starting from the discovery of a single plant entering the waxy ripening stage, the F2 population is treated by watering with agricultural drones. The flight altitude is set at 2.5-3m, and the spraying time is 10 am and 2 pm every day. The spraying cycle continues until all F2 populations enter the waxy ripening stage.

5. The breeding method for rice resistant to panicle germination according to claim 1, characterized in that: The specific method for field selection in step (3) is as follows: In the field, select single plants that have not tilted significantly, have not sprouted panicles, and have good agronomic traits. Take two panicles from each selected single plant, number them, and hang them on tags. Soak the selected rice panicles for 20-24 hours, wrap them with a damp cloth, then wrap them with plastic wrap and place them in an incubator. Starting from the second day, take out the selected single plants every 12 hours, soak them for 10-15 minutes, then wrap them with a damp cloth and plastic wrap and place them in an incubator. Continue this process until the sixth day. On the seventh day, the selected single rice ears are taken out, dried in the sun, and the sprouted seeds are removed. The remaining ears are kept for sowing in the next season.

6. The breeding method for rice resistant to panicle germination according to claim 1, characterized in that: In step (5), within a temperature-controlled multi-span greenhouse, a drone was used to simulate the plum rain season to conduct a large-scale, highly reproducible final identification of the panicle germination tolerance of stable rice varieties. The specific steps were as follows: The selected rice varieties of the three growth stages were transplanted to three multi-span greenhouses with a height of 2.5-3m. The top and sides of the multi-span greenhouses were equipped with film-rolling devices to control the opening and closing. The control variety was set as Koshihikari, which was sown in three stages to ensure that each variety had a corresponding Koshihikari that entered the waxy ripening stage at the same time. Each variety near the perimeter of the multi-span greenhouse was planted 1.5-2.5m away from the perimeter of the greenhouse. 35-40 days after the rice headed out, the film-rolling device on the top of the multi-span greenhouse was opened, and an agricultural drone was turned on to spray water at a height of 2.5-3m above the multi-span greenhouse. After spraying, the film-rolling device on the top of the multi-span greenhouse was closed. Spraying was carried out at 10:00 AM and 2:00 PM every day for 6 consecutive days. Sampling and screening of panicle germination tolerance varieties were conducted.

7. The breeding method for rice resistant to panicle germination according to claim 6, characterized in that: In step (5), when transplanting rice of the three growth stages, each rice variety is divided into 3 replicates, and each replicate is planted with 48 plants, specifically in 4 rows with 12 plants per row; the plant spacing is 7.5 inches × 4 inches.

8. The method for breeding rice resistant to panicle germination according to claim 4 or 6, characterized in that: The parameters for drone-based precipitation are as follows: spray volume is set to 150-200L per acre, 5-10mg gibberellin is added per liter of water, and flight speed is set to 3-5m / s.

9. The method for breeding rice resistant to panicle germination according to claim 6, characterized in that: The temperature control method in the multi-span greenhouse is as follows: 8 minimum and maximum thermometers are evenly arranged in each multi-span greenhouse to monitor the temperature uniformity and day-night temperature changes. The greenhouse temperature is controlled between 28 and 32°C during the day; when the temperature exceeds 35°C, the film rolling device is opened and water is poured in to cool it down; when the temperature is below 25°C, the film rolling device is closed to keep it warm; and all film rolling devices are closed at night.

10. The method for breeding rice resistant to panicle germination according to claim 6, characterized in that: The specific method for sampling and screening resistant spikelet germination lines is as follows: Select lines that do not tilt, take 3 replicates for each line, and take 5 consecutive plants starting from the third plant in the second row for each replicate; bring them back to the laboratory to investigate spikelet germination, and compare spikelet germination with that of Koshihikari, which also enters the waxy ripening stage at the same time. Those with a germination rate lower than Koshihikari are retained, and those with a higher germination rate are eliminated.

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