Drought resistance cotton genotypes evaluation with multi-year & multi-site study

To determine the agronomic traits closely related to the drought resistance of cotton, and the universal genotypes for drought resistance in cotton. The experiment was conducted in Alaer, Xinjiang Uygur Autonomous and Dunhuang, Gansu Province between 2020 and 2021. 199 cotton genotypes were selected, six agronomic traits: plant height (PH), boll number (BN), single boll weight (SBW), lint percentage (LP), first vegetative shoot length (FVSL), seed cotton yield (SCY) were measured and analyzed. Principal component analysis (PCA) and correlation analysis were conducted on the basis of drought resistance coefficient (DC) value of each agronomic trait. The comprehensive drought coefficient (CDC), drought resistance comprehensive evaluation values (D), and weight drought resistance coefficient (WDC) values were then calculated, and multiple regression analysis was performed with the DC value as the independent variable, the CDC, D, and WDC values serving as dependent variables. Cluster analysis was conducted on the basis of the CDC, D, and WDC values. The results from Alaer and Dunhuang indicated, drought stress significantly reduced the growth of all six agronomic traits. The degree of variation between the two sites varied greatly, indicating that environmental factors affected the response of agronomic traits to drought stress. Correlation analysis revealed that there were significant differences in each agronomic trait correlation between the two sites. Principal component analysis (PCA) indicated that PH, SBW and SCY were stable across both sites, but LP and FVSL were sensitive to environment. Multivariate analysis indicated that compared with CDC and WDC values, D value objectively reflects the contribution of different agronomic traits to drought resistance, with significant differences in the equation coefficients of the six agronomic traits between the two sites. Cluster analysis grouped the 199 cotton genotypes into four groups: high drought resistance, drought resistance, drought sensitive and high drought sensitive, with different allocations at the two sites. Most genotypes exhibited significant differences in drought resistance across the two sites, just seven genotypes: UC016, UC032, UC067, UC073, UC135, UC154 and UC173, presented consistent and universal drought resistance. Among these, UC067, UC154, and UC173 presented relatively high yields and could be used as high-yield and high-drought resistant genotypes.