Variety Screening And Association Analysis Of Drought Tolerance With Phenotypic Traits In Cotton

Allotetraploid upland cotton(Gossypium hirsutum L.;AADD,2n=4x=52)is one of the most important economic crops and the most significant natural fiber in our country and the raw materials of textile industries and the defense departments.At present,with the sharp adjustment of cotton areas in China,cotton planters have moved to cities and towns as well as participated in the secondary and tertiary industries,and the major cotton planting region gradually has moved to northwest territories in China.By 2017,Xinjiang's cotton yield accoured for 80.8% of the total production.There are rich solar-thermal resources in this region and shortages of water resource has tremendously effected plant height,the growth of root and some agronomic traits and finally resulted in decline of yield and fire quality.Hence,screeing higher drought-resistant cotton lines can provide materials for production and studying drought resistance of cotton can provide theoretical basis in order to explore molecular mechanism of drought resistance.In this study,we conducted identification and indices screening of drought tolerance for upland cotton from five ecological areas including NW(the northwest inland region),YR(Yellow River valley region),YZR(Yangtze River valley region),NEM(the northern specific early maturation region)and FR(Foreign region).Meanwhile,we condected Genome Wide Association Study(GWAS)according to genetic data and phenotypic data for CWS,EWS,LC and LT traits in order to find some QTLs or genes associated with dtought resistance and further explor molecular mechanism of drought resistance and explain scientic problems.The main results are as follows.1.We researched and analyzed 12 agronomic traits,which includes plant height,lint percentage,single boll weight,the first node of fruit branch,height of the first branch,effective boll number,fruit branch number,cotton seed yield,fiber length,specific breaking length,uniformity and micronaire.Meanwhile,we found the shortage of water effected seriously these traits what had siginicant difference except the trait the first node of fruit branch.2.We conducted identification and indices screening of drought tolerance for 153 upland cotton.We screened five drought-resistant indices including plant height,cotton seed yield,effective boll number,fruit branch number and single boll weight by these methods of membership function,principal component analysis,association analysis and clustering analysis at flowering and boll setting stage in upland cotton germplasm resources under normal water condition and drough stress and we can better evaluate derectly the drought resistance of upland cotton at flowering and boll setting stage.Meanwhile,we gained D(drought resistance comprehensive evaluation)value,CDC(comprehensive drought resistance coefficient)value and WDC(weight drought resistance coefficient)value and found yield of cotton has positive correlativity with D(drought resistance comprehensive evaluation)value,CDC(comprehensive drought resistance coefficient)value and WDC(weight drought resistance coefficient)value based on the comprehensive drought coefficient and association analysis.Finally,we identified two varieties Israel 1101 and yanzao 2,which were identified as drought resistant and sensitive upland cotton varieties at flowering and boll setting stage,respectively and other accessions are in between drought resistant and sensitive upland cotton varieties,which can provide important materials for the study of the mechanism of drought resistance.3.All of the 316 upland cotton cultivars and lines were conducted to plant at greenhouse of Cotton Research Institute of Chinese Academy of Agricultural Sciences and four traits including EWS,CWS,LT and LC were investigated.When the seedings of upland cotton were under drought stress,we found cotyledon of seedings was wilt early and then euphylla became gradually wilt.Leaf temperature of lines with drought resistance is lower than leaf temperature of sensitive accessions.There are of significance for LC.4.According to analysis of phylogenetic relationship,we found that Stonevill 2B(STV2B)was divided into YR(Yellow River valley region in China)group,which some accessions were together with Deltapine 20,and YZR group included Deltapine 14,Deltapine 15 and Deltapine 531.According to the result of GWAS for 316 upland cotton accessions,17 SNPs were located at chromosome A01,A05,A11 and D03 via other traits(CWS,EWS and LT).Importantly,in candidate regions,GhCIPK6,SnRK2.6 and WRKY70 which were involved in the response to abscisic acid(ABA),jasmonic acid(JA)and the mitogen-activated protein kinase(MAPK)signaling pathway,calcium transduction pathways were found and showed up-regulated under drought stress.Meanwhile,the gene GhCIPK6 was observed and identified significant differences under the severe drought condition within and the G8 variety by using RNA-seq analysis.