Evaluation Of Salt Tolerance Of Upland Cotton (Gossypium Hirsutum L.) And Its Correlation With SNP

Cotton is an important cash crop in China and a pioneer crop in saline and alkaline land.In recent years,in order to alleviate the contradiction of China's grain and cotton,cotton gradually transferred to the saline dryland,which put forward higher requirements on the salt tolerance of cotton varieties.screening and establishing a simple and effective method for evaluating salt tolerance of cotton,determining the salt tolerance of germplasm resources and screening the salt tolerance related molecular markers,have great significance for salt tolerance breeding of cotton.The study was conducted under salt stress.Through investigating the correlation between Germination and seedling stage and salt tolerance of cotton seedlings,A simple and rapid identification index of salt tolerance was screened out.A number of salt related molecular markers were screened by association analysis.It will provide reference for the innovation of salt tolerant germplasm and breeding of new varieties of cotton.The main results are as follows:1.The interval distribution of salt tolerance coefficient of different characters showed that the salt sensitive characters were different at different developmental stages.At seedling stage,root length,root fresh weight,root dry matter and germination potential were sensitive to salt stress,while germination index,vigor index and shoot fresh quality were relatively slow to salt stress.At seedling stage,stomatal conductance was most affected by salt stress,while aboveground dry mass,root fresh weight and root dry mass were relatively slow.2.Path analysis of comprehensive value(D)of salt tolerance was carried out among all characters.The result shows that dry weight,germination rate,germination potential can be used as indexes of salt tolerance period adorable seedling shoot seedling,shoot fresh weight,net photosynthetic rate,transpiration rate,plant height,leaf area can be used as screening indexes of salt tolerance at seedling stage.3.Descriptive statistics and differential significance analysis indicated that there was a great variability at germination stage and seedling stage of 196 upland cotton in salt tolerance.According to the comprehensive value of salt tolerance,the salt tolerance grades of196 materials were divided into 3 categories: high tolerance,salt tolerance and salt sensitivity.The difference in salt tolerance of different source materials is large.Domestic material have better salt resistance than foreign materials.Xinjiang,Shandong,Zhongmiansuo have outstanding performance.4.The genetic diversity of 196 Upland Cotton Germplasms was analyzed by 41814 SNPs.The average polymorphism information content was 0.23,and the genetic polymorph-ism was 0.095-0.375.The range of gene diversity in each locus was 0.1-0.5,and the average diversity index of each locus was 0.28,indicating that there were abundant genetic diversity among the materials,which was consistent with the phenotypic analysis.5.Association analysis based on MLM model.At significant level(-log10P>4),34 salt related loci were detected at seedling stage and 45 salt tolerant loci at seedling stage.These results provide a reference for further research on salt tolerance germplasm innovation,variety selection and salt tolerance mechanism in cotton.