Exploration Of Excellent Allelic Variation Of Soybean Seedling Traits In Saline-alkali Stress Tolerance

China's saline-alkali land is characterized by large area,wide distribution and multiple types.There are 99.133 million hm~2saline-alkali soil,accounting for saline-alkali and other marginal land for agricultural production is one of the important ways to improve crop yield.Breeding salt-tolerant soybean varieties is the most effective and economical way to solve the salinization problem.Soybean seedling stage is sensitive to salt-alkali stress,and it is also the key stage in the growth cycle.Therefore,the study of salt-alkali tolerance traits in soybean seedling stage and the discovery of relevant marker loci and excellent alleles are germplasm resources,and have important guiding significance for soybean salt-alkali tolerance breeding.The neutral salt(100mmol/L Na Cl solution)and alkaline salt(20mmol/L Na₂CO₃solution)were used to carry out saline-alkali stress treatment in the seedling stage of soybean growth.The control group was treated with distilled water.The salt and alkali tolerance of varieties were evaluated.Combined with 210 pairs of SSR markers covering 20 chromosomes of soybean,the association analysis of phenotypic and marker was conducted to further explore the excellent alleles and vector materials associated with soybean seedling saline-alkali tolerance traits.1.Statistical analysis was conducted on the relative traits of 7 tested cultivars under salt-alkali stress in 2019-2020.The genetic variation coefficient of salt-alkali tolerance traits index was 16.59%-59.95%in the tested population under salt stress,and 10.65%-68.54%in the tested population under salt-alkali stress.The results of phenotypic variation showed that the genetic variation coefficient of relative fresh leaf weight was the highest and the genetic variation coefficient of relative fresh leaf weight was the lowest under different varieties and stress treatments.and the extreme salt tolerance varieties were shuangxiaojinhuang,kaiyu no.3,Jilin No.29 and Jingshanpu.2.The soybean population structure was analyzed,and the results showed that the population was divided into 9 subgroups.LD linkage imbalance results showed that there were 21,945 loci combinations detected in 166 soybean varieties,and 870collinear combinations were detected.The minimum attenuation distance extended was3.13c M.3.General linear model was used for association analysis of soybean varieties,and 14 markers were associated with 7 salt-alkali tolerance traits in 2019-2020,and 30markers were associated with each trait in total,contributing 2.79%-18.29%to the relative phenotypic value.From 2019 to 2020,29 markers were associated with 7salt-alkali tolerance traits,and 63 markers were associated with them in total,contributing 3.78%to 38.07%of their phenotypic values.Three markers were associated with two relative traits in salt stress tolerance test,and six markers were associated with two or more traits in salt and alkali stress test,among which two markers were associated with three traits.The association between the same marker locus and multiple relative traits may be due to the genetic basis of trait correlation and even gene pleiotropy.A total of 7 two-year identical gene sequences related to controlling seedling salt tolerance were found in salt-alkali stress tolerance,and 5two-year identical gene sequences related to salt-alkali stress tolerance were found in salt-alkali stress tolerance,all of which were verified to be related to plant resistance expression under abiotic stress such as salt-alkali stress in previous studies.4.Based on further analysis of loci excavated under salt-alkali stress,42 and 78excellent alleles with synergistic effect were found in salt stress tolerance and salt-alkali stress tolerance at seedling stage in this study.Excellent alleles sat-064-140bp and sat-064-148bp simultaneously increased the phenotypic effect values of relative cotyl length and relative hypocotyl length.Sat-267-189bp increased the phenotypic effect values of relative cotyl length and relative hypocotyl length under salt stress,and also increased the relative cotyl length and leaf fresh weight under salt-alkali stress.In the resistance to salt stress test and salinity-alkalinity stress test,respectively for the carrier of 10 different materials,and jilin 14 little golden-1 in resistance to salt stress tests at the same time carry multiple has excellent synergistic effect of allelic variation,the no.3 and open education in resistance to salt stress test and 3 salinity-alkalinity stress tests were carried with excellent synergistic effect of allelic variation,These varieties can aggregate multiple excellent alleles of salt-tolerant traits of seedlings,which can be fully utilized in salt-tolerant breeding.The salt-tolerant soybean varieties,associated loci,gene sequences,excellent alleles and corresponding vector materials screened out in this study can provide an important theoretical basis for subsequent molecular salt-tolerant breeding of soybean.