Identification And GWAS Of Drought Tolerance At Whole Growth Period In Cotton Germplasm Resources And Drought Resistance Index Screening

To screen the identification index of drought resistance of cotton during the whole growth period and the resources of drought-resistant cotton varieties,and to provide theoretical basis and basic materials for the breeding of new drought-resistant cotton varieties.199 cotton varieties with different drought resistance were used,they come from NW(the northwest inland region),YR(Yellow River valley region),YZR(Yangtze River vallery region),NEM(the northern specific early maturation region)and FR(Foreign region),treated with normal irrigation and drought stress,and drought treatment was carried out during the whole growth period.The indexes of plant height,boll number,boll weight and soluble sugar content were selected,and drought resistance coefficient,principal component analysis,grey correlation analysis and cluster analysis were used to comprehensively evaluate the drought resistance of 199 cotton variety resources during the whole growth period and screen the drought resistance index.By analyzing the variation coefficient of each test point data,the coefficient of variation of lint percentage is the smallest,while the coefficient of variation of seed cotton yield and aingle plant all vegetative shoot length is larger.At the same time,the DC value range of seed cotton yield is wider,while the DC value range of single boll weight and lint percentage is smaller,indicating that the seed cotton yield is more seriously affected by drought,while the DC value range of single boll weight and lint percentage is less affected.According to the principal component analysis of each agronomic trait,drought stress has obvious effect on plant development,especially on plant height development.By comparing the correlation degree between DC value and D value of four experiments,it is found that single plant first vegetative shoot length and single plant all vegetative shoot length ranked higher in the ranking of correlation degree,while the lint percentage ranked lower in the ranking of correlation degree.However,the correlation degree between DC and WDC values was significantly different among the four point tests.Finally,five cotton varieties with better drought resistance were selected in this experiment:UC020,UC030,UC023,UC042 and UC066.At the same time,GWAS is used to combine the agronomic trait data of two-year four-point experiment with 199 cotton genome resequencing data to obtain 81 SNPs loci,and to screen out several candidate genes related to drought resistance,which are located on A06,A07 and D04 chromosomes.Among them,four agronomic traits,namely,2019 Huyanghe SSC,2019 Huyanghe SPFVSL,2019 Huyanghe SPAVSL and 2020 Huyanghe SPAVSL,are all associated with an SNP(A07:26180293).Two candidate genes Gh＿A07G1192 and Gh＿A07G1198 are found near this SNP,these two candidate genes performe well in the previous laboratory drought resistance test data,indicating that these two genes may be closely related to the drought resistance of cotton.The next step is to identify these SNPs through RNA interference,transgenic methods and other methods to reveal the mechanism of cotton drought resistance and provide theoretical basis and molecular materials for cotton drought resistance breeding.