Mutagenesis seedling raising method for gene mutation rice in cold region saline-alkali soil

Abstract

The invention relates to the technical field of rice seedling raising, and discloses a mutagenesis seedling raising method for gene mutation rice in cold region saline-alkali soil, which comprises the following steps: S1, mutant screening and grain type mutant library construction: carrying out mutagenesis treatment on rice seeds with cold-resistant and saline-alkali-resistant characteristics, culturing, and screening out seeds of plants with significant variation grain types; s2, grain type gene mining and resistance screening: screening out seeds of plants with excellent grain type and excellent comprehensive character performance in a saline-alkali soil environment, and carrying out multi-generation single plant selection and selfing purification; a new germplasm resource with stable inheritance and expression of standard characters is obtained; s3, performing multi-character polymerization and variety breeding: performing hybrid combination on the new germplasm resources, and selecting hybrid plants with excellent comprehensive states; and then carrying out a comparative test to breed a strain with remarkably excellent comprehensive characters. The rice seeds bred through the method have the advantages of being good in saline-alkali resistance and cold resistance, high in adaptability to extreme environments, good in plant stability and high and stable in yield.

Description

Technical Field

[0001] The invention relates to the technical field of rice seedling cultivation, in particular to a method for inducing mutation of gene-mutated rice in saline-alkali soil in cold regions. Background Art

[0002] As one of the world's most important food crops, rice cultivation has always been affected by various natural and human factors. The most important factor is the nature of the soil, especially the degree of soil salinization. Salt-alkali damage is one of the important limiting factors in rice production. Therefore, conducting research on rice salt-alkali tolerance and rationally developing and utilizing saline-alkali land to grow rice are of great significance to my country's food security.

[0003] A Chinese patent discloses a method for cultivating stress-resistant rice seedlings in cold-region saline-alkali soils (Announcement No. CN116458399A). This patented technology combines seed treatment, seedling treatment, and seedbed treatment to cultivate and treat the stress resistance of the seedlings in advance throughout the entire seedling cultivation process. At the same time, by providing the seedlings with sufficient ingredients, it can better promote the development of the seedling rootstock and its stress resistance, facilitating subsequent transplanting and planting. However, its adaptability to extreme environments is not strong, and the plant stability is poor. Summary of the Invention

[0004] The object of the present invention is to provide a method for inducing mutation and raising rice seedlings in saline-alkali soil in cold regions, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for inducing mutation and raising rice seedlings in saline-alkali soil in cold regions comprises the following steps: S1. Mutant screening and construction of a grain type mutant library: Select rice seeds with cold resistance and salt-alkali resistance as parent seeds; treat the parent seeds with a combined mutagenesis method to obtain mutagenized seeds, i.e., the M1 generation; sow the M1 generation in a seedbed not exposed to salt-alkali stress, grow normally to maturity, and harvest seeds of the M1 generation, i.e., the M2 generation; sow the M2 generation in a test field not exposed to salt-alkali stress, grow normally to maturity; screen out individual plants with significantly different grain types; and test these plants, i.e., the M3 generation, to construct a grain type mutant library; S2. Grain shape gene mining and resistance screening: Establish a saline-alkali soil environment that simulates the target rice planting area, plant the M3 generation in a simulated cold saline-alkali stress environment, and grow to maturity; screen out individual plants with excellent grain shape and comprehensive traits, and test them, i.e., the M4 generation; select two individuals from the M4 generation that show extreme differences in grain shape and stress resistance; i.e., the two individuals with the best and worst performance in grain shape and stress resistance, perform genome sequencing and bioinformatics analysis to obtain candidate gene intervals, and then screen out individual plants carrying excellent alleles. Perform multiple generations of individual plant selection and self-pollination purification in the target cold saline-alkali soil environment; obtain new germplasm resources with stable inheritance and expression of target traits, i.e., stable strains; S3. Multi-trait aggregation and variety breeding: The new germplasm resources obtained in step S2 are hybridized and combined to obtain hybrid plants that aggregate multiple excellent traits, namely the F1 generation; the offspring of the F1 generation hybrid plants, namely the F2 generation and later generations, are planted to select hybrid plants with excellent comprehensive status; then, multi-point and multi-year variety comparison tests are carried out in the target planting area to select varieties with significantly excellent comprehensive traits.

[0006] As a further solution of the present invention: in the step S1, the specific methods for mutant screening and particle type mutant library construction are as follows: S11. Parent Seed Selection: Based on the specific characteristics of the target cold-region saline-alkali soil area, cold-region rice varieties with cold-resistance and salt-alkali resistance are selected as mutagenic parents. Among these rice varieties, healthy and plump seeds are selected and disinfected to obtain parent seeds. S12, combined mutagenesis treatment: treating parent seeds in batches by combining physical mutagenesis and chemical mutagenesis to obtain mutagenized seeds, i.e., the M1 generation; S13, M1 generation planting and management: sow the M1 generation in a seedbed that is not under saline-alkali stress, allow the M1 generation plants to grow normally to maturity, and harvest the M1 generation seeds, i.e., the M2 generation; S14. Construction of the M2 generation grain type mutant library: The M2 generation was sown according to the strains in the experimental field without saline-alkali stress to form a large number of M2 generation populations; at the maturity stage, the grain shape of individual plants in each M2 strain was observed and recorded; individual plants with significant grain shape variation were screened and tested, i.e., the M3 generation, to construct the grain type mutant library.

[0007] As a further solution of the present invention: in the S12 step, the means of physical mutagenesis include gamma rays, ion beams and space mutagenesis, and the radiation dose that can make the seed survival rate between 50% and 70% is determined through preliminary experiments as the optimal radiation dose; the means of chemical mutagenesis include EMS-ethyl methanesulfonate and NaN3-sodium azide, and the reagent concentration and treatment time that can make the seed germination rate between 40% and 60% are determined through preliminary experiments as the optimal reagent concentration and treatment time.

[0008] As a further solution of the present invention: in the step S2, the specific method of grain type gene mining and resistance screening is as follows: S21. Analysis of cold-region saline-alkali soil characteristics and establishment of stress simulation environment: Analyze the physical and chemical properties and main stress factors of the cold-region saline-alkali soil in the target planting area, and establish an environment simulating the target planting area under cold-region saline-alkali stress; S22. Phenotypic identification and screening of grain-shape mutants: Plant the M3 generation in a simulated cold-climate saline-alkali stress environment and grow until maturity. Observe and evaluate their agronomic traits and stress resistance under saline-alkali stress. Select individual plants with excellent grain shape and overall performance, and test them as the M4 generation. S23. Candidate gene mining: From the M4 generation, two individuals with extreme differences in grain shape and stress resistance were selected, i.e., the best and worst performers in grain shape and stress resistance. DNA was extracted from these two individuals and mixed in equal amounts for genome sequencing. The sequenced genomes were subjected to bioinformatics analysis, and combined with known information on rice grain shape and stress resistance genes, genes within the candidate gene interval were ranked. S24. Candidate gene verification and breeding screening: Through molecular verification and functional verification methods, the candidate genes that have been verified to be effective are molecularly marked, and single plants carrying excellent alleles are screened. S25. Creation of stable and excellent germplasm resources: Single plants carrying excellent alleles are screened out and subjected to multiple generations of single plant selection and self-pollination purification; each generation is screened in the target cold-region saline-alkali soil environment to ensure the stable inheritance and expression of target traits in new germplasm resources, i.e. stable strains.

[0009] As a further solution of the present invention: in step S23, the specific method of performing bioinformatics analysis on the sequenced genome is as follows: S231. Compare the genomes of two individuals showing extreme differences in grain shape and stress resistance with the reference genome; calculate the single nucleotide polymorphism index difference between the two individuals in each genomic region; S232. The genomic intervals significantly enriched in individuals with the best grain shape and stress resistance performance were selected as candidate gene intervals, and the genes within the candidate gene intervals were ranked based on the known information on rice grain shape genes and stress resistance genes.

[0010] As a further solution of the present invention: in the step S24, The molecular validation method is as follows: genotyping of candidate gene regions using molecular markers to verify their association with the target trait; The functional verification method is as follows: Transgenic technology is used to verify the function of the candidate gene in the target parent.

[0011] As a further solution of the present invention: in the step S3, the specific method of multi-trait aggregation and variety breeding is as follows: S31. Parent selection and hybrid design: Using new germplasm resources as core parents, analyze the strengths and weaknesses of each parent, design hybrid combinations, and obtain hybrid plants with multiple excellent traits, namely the F1 generation; S32. Field stress screening and molecular marker-assisted selection: Plant the offspring of the F1 hybrid plants, i.e., the F2 generation and later generations. Use field stress screening and molecular marker selection to simultaneously select for multiple complex traits in the plant line to obtain plants with excellent overall performance. S33. Advanced strain identification and stability testing: Identify stable strains among plants with excellent overall performance; conduct multi-site, multi-year comparative trials in target cold saline-alkali soil regions; and comprehensively and systematically evaluate their agronomic traits, yield, quality, stress resistance, adaptability, and stability. S34. Breeding and industrialization of new varieties: Screen out varieties with significantly superior comprehensive traits, pass variety approval at the provincial level or above, obtain new variety rights, and realize industrial promotion.

[0012] As a further embodiment of the present invention, in step S32, the field stress screening method is as follows: comprehensively evaluating multiple complex traits of the plant lines in the target cold saline-alkali soil environment throughout the entire growth period; eliminating individuals with poor comprehensive traits; The method of molecular marker-assisted selection is as follows: Molecular markers are used to select genotypes in early generations and quickly aggregate target genes for multiple traits.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention first performs a mutagenesis treatment on rice seeds with cold-resistant and salt-alkali-resistant characteristics, cultivates and screens seeds with significantly variant grain shapes, and constructs a grain shape mutant library; then simulates the saline-alkali land environment of the target rice planting area, performs multi-generation single plant selection and self-pollination purification, and obtains new germplasm resources with stable inheritance and expression of target traits; then hybridizes the new germplasm resources and selects varieties with significantly excellent comprehensive traits; the rice seeds bred by this method have good salt-alkali and cold-resistant properties, strong adaptability to extreme environments, good plant stability, and the characteristics of high and stable yield. DETAILED DESCRIPTION

[0014] In an embodiment of the present invention, a method for inducing mutation and raising rice seedlings in saline-alkali soil in cold regions comprises the following steps: S1. Mutant screening and construction of a grain type mutant library: Select rice seeds with cold resistance and salt-alkali resistance as parent seeds; treat the parent seeds with a combined mutagenesis method to obtain mutagenized seeds, i.e., the M1 generation; sow the M1 generation in a seedbed not exposed to salt-alkali stress, grow normally to maturity, and harvest seeds of the M1 generation, i.e., the M2 generation; sow the M2 generation in a test field not exposed to salt-alkali stress, grow normally to maturity; screen out individual plants with significantly different grain types; and test these plants, i.e., the M3 generation, to construct a grain type mutant library; S2. Grain shape gene mining and resistance screening: Establish a saline-alkali land environment that simulates the target rice planting area, plant the M3 generation in a simulated cold-region saline-alkali stress environment, and grow to maturity; screen out individual plants with excellent grain shape and comprehensive traits, and test them, i.e., the M4 generation; select two individuals from the M4 generation that show extreme differences in grain shape and stress resistance, including saline-alkali resistance and cold resistance; i.e., the two individuals with the best and worst performance in grain shape and stress resistance, and perform genome sequencing and bioinformatics analysis to obtain candidate gene intervals, and then screen out individual plants carrying excellent alleles, and conduct multiple generations of individual plant selection and self-pollination purification in the target cold-region saline-alkali soil environment; obtain new germplasm resources with stable inheritance and expression of target traits, i.e., stable strains; S3. Multi-trait aggregation and variety breeding: The new germplasm resources obtained in step S2 are hybridized and combined to obtain hybrid plants that aggregate multiple excellent traits, namely the F1 generation; the offspring of the F1 generation hybrid plants, namely the F2 generation and later generations, are planted to select hybrid plants with excellent comprehensive status; then, multi-point and multi-year variety comparison tests are carried out in the target planting area to select varieties with significantly excellent comprehensive traits.

[0015] Preferably, in step S1, the specific methods for mutant screening and particle type mutant library construction are as follows: S11. Parent Seed Selection: Based on the specific characteristics of the target cold-region saline-alkali soil area, such as salinity type, salinity level, and cold stress level, consider the specific content ranges of NaCl, Na2SO4, Na2CO3, and NaHCO3 in salinity type; pH, EC value, and ion composition in salinity level; and cold stress level, such as early spring low temperatures and frost frequency. Select cold-region rice varieties with cold- and salinity-resistant characteristics as mutagenic parents. Select healthy and plump seeds from these rice varieties and disinfect them to obtain parent seeds. S12, combined mutagenesis treatment: treating parent seeds in batches by combining physical mutagenesis and chemical mutagenesis to obtain mutagenized seeds, i.e., the M1 generation; S13. Planting and management of the M1 generation: Sow the M1 generation in a seedbed free of saline-alkali stress to allow the induced seeds to germinate and grow normally. Ensure that the M1 generation plants grow normally to maturity and harvest the M1 generation seeds, i.e., the M2 generation. Since M1 generation plants are usually chimeras, meaning mutations occur in some cells, their seeds (M2 generation) are the main source of isolated mutants. Therefore, seeds of M1 generation plants must be harvested individually. S14. Construction of the M2 generation grain type mutant library: The M2 generation is sown in the experimental field without saline-alkali stress according to the plant line (the offspring of each M1 plant is a plant line) to form a large number of M2 generation groups; at the maturity stage, the grain shape of each individual plant in each M2 plant line is observed and recorded, such as grain length, grain width, aspect ratio, and grain weight; individual plants with significant grain shape variation, such as those with extra-large grains, extra-long grains, extra-round grains, and extra-heavy grains are screened out; and these plants are tested, i.e., the M3 generation, to construct the grain type mutant library.

[0016] Preferably, in step S12, the means of physical mutagenesis include gamma rays, ion beams and space mutagenesis, and the radiation dose that can make the seed survival rate between 50% and 70% is determined through preliminary experiments as the optimal radiation dose to avoid the radiation dose being too high to cause death or too low to cause ineffectiveness; the means of chemical mutagenesis include EMS-ethyl methanesulfonate and NaN3-sodium azide, and the reagent concentration and treatment time that can make the seed germination rate between 40% and 60% are determined through preliminary experiments as the optimal reagent concentration and treatment time, that is, the seed germination rate is significantly reduced but not completely inhibited between 40% and 60%.

[0017] Preferably, in step S2, the specific methods of grain type gene mining and resistance screening are as follows: S21. Analysis of Cold-Region Saline-Alkali Soil Characteristics and Establishment of Stress Simulation Environment: Analyze the physical and chemical properties and major stress factors of the cold-region saline-alkali soil in the target planting area, including properties such as salt type, content, pH, organic matter, and texture; major stress factors such as low temperature and salinity-alkali interaction; and establish an environment simulating the target planting area under cold-region saline-alkali stress, such as using a greenhouse or artificial climate chamber to set different gradients of salinity, alkalinity, and low temperature. S22. Phenotypic identification and screening of grain-shape mutants: The M3 generation was planted in a simulated cold-region saline-alkali stress environment and grown to maturity. Agronomic traits and stress resistance indicators under saline-alkali stress were observed and evaluated. Agronomic traits included survival rate, growth potential, number of tillers, plant height, growth period, and yield components; yield components included number of effective ears, number of grains per ear, fruit set rate, and 1000-grain weight; and stress resistance indicators included saline-alkali damage index, chlorophyll content, relative conductivity, proline content, SOD antioxidant enzyme activity, POD antioxidant enzyme activity, and cold tolerance score. Individual plants with excellent grain shape and comprehensive traits, such as stress resistance and yield potential, were selected and tested, i.e., the M4 generation. S23. Candidate gene mining: From the M4 generation, two individuals with extreme differences in grain shape and stress resistance are selected, i.e., the two individuals with the best and worst performance in grain shape and stress resistance. For example, the individual with the largest grain shape and the strongest salt-alkali and cold-resistance is selected as the superior pool, and the individual with the smallest grain shape and the weakest salt-alkali and cold-resistance is selected as the control pool. DNA is extracted from the two individuals and mixed in equal amounts for genome sequencing. For example, DNA is extracted from individuals in the superior pool and the control pool and mixed in equal amounts for genome sequencing. The sequenced genomes are subjected to bioinformatics analysis, and the genes within the candidate gene interval are ranked based on known information on rice grain shape genes and stress resistance genes. S24. Candidate gene verification and breeding screening: Through molecular verification and functional verification methods, the candidate genes that have been verified to be effective are molecularly marked, and single plants carrying excellent alleles are screened. S25. Creation of stable and excellent germplasm resources: Single plants carrying excellent alleles are screened out and subjected to multiple generations (such as M5 to M8 generations) of single plant selection and self-pollination purification; each generation is screened in the target cold-region saline-alkali soil environment to ensure the stable inheritance and expression of new germplasm resources, i.e. stable strains; target traits include excellent grain shape, salt-alkali tolerance and cold tolerance.

[0018] Preferably, in step S23, the specific method for performing bioinformatics analysis on the sequenced genome is as follows: S231. Compare the genomes of two individuals showing extreme differences in grain shape and stress tolerance to a reference genome, i.e., a known, verified rice seed genome sequence, including known rice grain shape genes such as GS3, GW2, GW5, and GS5, and known rice stress tolerance genes such as OsHKT, OsNHX, DREB, and COR; and calculate the single nucleotide polymorphism index difference (SNP index difference, ΔSNP-index) between the two individuals in each genomic region. S232. The genomic intervals that are significantly enriched in the individuals with the best grain shape and stress resistance performance (i.e., the excellent pool) are used as candidate gene intervals. The significantly enriched genomic intervals are the ΔSNP-index peak regions. The genes within the candidate gene intervals are ranked based on the known information on rice grain shape genes and stress resistance genes.

[0019] Preferably, in step S24, the molecular verification method is as follows: genotyping the candidate gene region using molecular markers (such as KASP, dCAPS) to verify its association with the target trait; Functional validation methods are as follows: Use transgenic technology (such as overexpression, RNAi) to verify the function of the candidate gene in the target parent.

[0020] Preferably, in step S3, the specific method of multi-trait aggregation and variety breeding is as follows: S31. Parent Selection and Hybrid Design: Using new germplasm resources as core parents, analyze the strengths and weaknesses of each parent. For example, parent A has large grains and is salt-tolerant but has a long growing period, while parent B is cold-tolerant and early-maturing but has average grain shape. Design hybrid combinations to produce hybrid plants with multiple desirable traits, i.e., the F1 generation, such as large grains, strong salt and alkali tolerance, strong cold tolerance, a suitable growing period, and high yield potential. S32. Field stress screening and molecular marker-assisted selection: Plant the offspring of the F1 hybrid plants, i.e., the F2 generation and later generations. Use field stress screening and molecular marker selection to simultaneously select for multiple complex traits in the plant line to obtain plants with excellent overall performance. S33. Identification and stability testing of advanced strains: For stable strains with excellent overall performance, such as the F5 to F7 generations, conduct multi-site, multi-year comparative trials in target cold saline-alkali soil regions. Comprehensively and systematically evaluate their agronomic traits, yield, quality, stress resistance, adaptability, and stability. S34. Breeding and industrialization of new varieties: Screen out varieties with significantly superior comprehensive traits, pass variety approval at the provincial level or above, obtain new variety rights, and realize industrial promotion.

[0021] Preferably, in step S32, the field stress screening method is as follows: comprehensively evaluating multiple complex traits of the plant lines, such as grain shape, stress resistance, growth period, and yield composition, in the target cold saline-alkali soil environment throughout the entire growth period; eliminating individuals with poor comprehensive traits; The method of molecular marker-assisted selection is as follows: Molecular markers are used to perform genotype selection in early generations (such as F2 to F4 generations) to quickly aggregate target genes for multiple traits, thereby improving selection efficiency and overcoming the difficulty of aggregating multiple traits.

[0022] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for inducing mutation and raising rice seedlings in saline-alkali soil in cold regions, characterized in that: The following steps are involved: S1. Mutant screening and construction of a grain type mutant library: Select rice seeds with cold resistance and salt-alkali resistance as parent seeds; treat the parent seeds with a combined mutagenesis method to obtain mutagenized seeds, i.e., the M1 generation; sow the M1 generation in a seedbed not exposed to salt-alkali stress, grow normally to maturity, and harvest seeds of the M1 generation, i.e., the M2 generation; sow the M2 generation in a test field not exposed to salt-alkali stress, grow normally to maturity; screen out individual plants with significantly different grain types; and test these plants, i.e., the M3 generation, to construct a grain type mutant library; S2. Grain shape gene mining and resistance screening: Establish a saline-alkali soil environment that simulates the target rice planting area, plant the M3 generation in a simulated cold-region saline-alkali stress environment, and grow to maturity; screen out individual plants with excellent grain shape and comprehensive traits, and test them, i.e., the M4 generation; select two individuals from the M4 generation that show extreme differences in grain shape and stress resistance; i.e., the two individuals with the best and worst performance in grain shape and stress resistance, perform genome sequencing and bioinformatics analysis to obtain candidate gene intervals, and then screen out individual plants carrying excellent alleles, and conduct multiple generations of individual plant selection and self-pollination purification in the target cold-region saline-alkali soil environment; Obtain new germplasm resources with stable inheritance and expression of target traits, i.e. stable strains; S3, multi-trait aggregation and variety breeding: hybridizing the new germplasm resources obtained in step S2 to obtain hybrid plants that aggregate multiple excellent traits, i.e., the F1 generation; Plant the offspring of the F1 hybrid plants, i.e. the F2 and subsequent generations, and select hybrid plants with excellent overall conditions; then, conduct multi-point and multi-year variety comparison tests in the target planting area to select varieties with significantly excellent overall traits.

2. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 1, characterized in that: In step S1, the specific methods for mutant screening and particle type mutant library construction are as follows: S11. Parent Seed Selection: Based on the specific characteristics of the target cold-region saline-alkali soil area, cold-region rice varieties with cold-resistance and salt-alkali resistance are selected as mutagenic parents. Among these rice varieties, healthy and plump seeds are selected and disinfected to obtain parent seeds. S12, combined mutagenesis treatment: treating parent seeds in batches by combining physical mutagenesis and chemical mutagenesis to obtain mutagenized seeds, i.e., the M1 generation; S13, M1 generation planting and management: sow the M1 generation in a seedbed that is not under saline-alkali stress, allow the M1 generation plants to grow normally to maturity, and harvest the M1 generation seeds, i.e., the M2 generation; S14. Construction of the M2 generation grain type mutant library: The M2 generation was sown according to the strains in the experimental field without saline-alkali stress to form a large number of M2 generation populations; at the maturity stage, the grain shape of individual plants in each M2 strain was observed and recorded; individual plants with significant grain shape variation were screened and tested, i.e., the M3 generation, to construct the grain type mutant library.

3. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 2, characterized in that: In the S12 step, the means of physical mutagenesis include gamma rays, ion beams and space mutagenesis, and the radiation dose that can make the seed survival rate between 50% and 70% is determined through preliminary experiments as the optimal radiation dose; the means of chemical mutagenesis include EMS-ethyl methanesulfonate and NaN3-sodium azide, and the reagent concentration and treatment time that can make the seed germination rate between 40% and 60% are determined through preliminary experiments as the optimal reagent concentration and treatment time.

4. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 1, characterized in that: In step S2, the specific methods for grain type gene mining and resistance screening are as follows: S21. Analysis of cold-region saline-alkali soil characteristics and establishment of stress simulation environment: Analyze the physical and chemical properties and main stress factors of the cold-region saline-alkali soil in the target planting area, and establish an environment simulating the target planting area under cold-region saline-alkali stress; S22. Phenotypic identification and screening of grain-shape mutants: Plant the M3 generation in a simulated cold-climate saline-alkali stress environment and grow until maturity. Observe and evaluate their agronomic traits and stress resistance under saline-alkali stress. Select individual plants with excellent grain shape and overall performance, and test them as the M4 generation. S23. Candidate gene mining: From the M4 generation, two individuals with extreme differences in grain shape and stress resistance were selected, i.e., the two individuals with the best and worst performance in grain shape and stress resistance. DNA was extracted from these two individuals and mixed in equal amounts for genome sequencing. The sequenced genome was subjected to bioinformatics analysis, and the genes within the candidate gene interval were ranked based on known information on rice grain type genes and stress resistance genes. S24. Candidate gene verification and breeding screening: Through molecular verification and functional verification methods, the candidate genes that have been verified to be effective are molecularly marked, and single plants carrying excellent alleles are screened. S25. Creation of stable and excellent germplasm resources: Single plants carrying excellent alleles are screened out and subjected to multiple generations of single plant selection and self-pollination purification; each generation is screened in the target cold-region saline-alkali soil environment to ensure the stable inheritance and expression of target traits in new germplasm resources, i.e. stable strains.

5. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 4, characterized in that: In step S23, the specific method for performing bioinformatics analysis on the sequenced genome is as follows: S231. Compare the genomes of two individuals showing extreme differences in grain shape and stress resistance with the reference genome; calculate the single nucleotide polymorphism index difference between the two individuals in each genomic region; S232. The genomic intervals significantly enriched in individuals with the best grain shape and stress resistance performance were selected as candidate gene intervals, and the genes within the candidate gene intervals were ranked based on the known information on rice grain shape genes and stress resistance genes.

6. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 4, characterized in that: In the step S24, The molecular validation method is as follows: genotyping of candidate gene regions using molecular markers to verify their association with the target trait; The functional verification method is as follows: Transgenic technology is used to verify the function of the candidate gene in the target parent.

7. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 1, characterized in that: In step S3, the specific method of multi-trait aggregation and variety breeding is as follows: S31. Parent selection and hybrid design: Using new germplasm resources as core parents, analyze the strengths and weaknesses of each parent, design hybrid combinations, and obtain hybrid plants with multiple excellent traits, namely the F1 generation; S32. Field stress screening and molecular marker-assisted selection: Plant the offspring of the F1 hybrid plants, i.e., the F2 generation and later generations. Use field stress screening and molecular marker selection to simultaneously select for multiple complex traits in the plant line to obtain plants with excellent overall performance. S33. Identification and stability testing of advanced strains: Conduct multi-site, multi-year comparative testing of stable strains among plants with excellent overall condition in target cold saline-alkali soil areas; Comprehensive and systematic evaluation of its agronomic traits, yield, quality, stress resistance, adaptability and stability; S34. Breeding and industrialization of new varieties: Screen out varieties with significantly superior comprehensive traits, pass variety approval at the provincial level or above, obtain new variety rights, and realize industrial promotion.

8. The method for inducing mutation and raising rice seedlings in cold saline-alkali soil according to claim 7, characterized in that: In the step S32, the field stress screening method is as follows: comprehensively evaluating multiple complex traits of the plant lines in the target cold saline-alkali soil environment throughout the growth period; eliminating individuals with poor comprehensive traits; The method of molecular marker-assisted selection is as follows: Molecular markers are used to select genotypes in early generations and quickly aggregate target genes for multiple traits.