Determination of the Suitable indices for drought tolerance in cotton genotypes

To identify the drought tolerant genotypes an experiment was conducted in research farm of Faculty of Agriculture of Birjand University in 2014. Two separate experiments were conducted in a randomized complete blocks design with three replicates14 treatments. Cotton genotypes were: Armaghan, Oltan, Bakhtegan, Sahel, Si ecra, Shirpan 603, Khordad, Deltapine 25, Mehr, Varamin, N-200, SB35, SP371, 84-39-T3, respectively. Irrigations in normal and drought stress conditions were applied after 100 and 200 mm evaporation from class a tank. Comparison of different water stress indices showed that Stress Tolerance Index (STI), Mean Productivity (MP), Geometric Mean Productivity (GMP), Modified stress tolerance index for normal condition (K1STI) and Modified stress tolerance index for stress condition(K2STI) were the best indices that can be used to determine resistant genotypes. The most desirable genotypes at normal and stress conditions based on the above indices were Deltapine 25, Bakhtegan and SP731 respectively. Grouping of genotypes using cluster analysis method showed that Deltapine25, Bakhtegan and SP731 were water deficit tolerant genotypes with high yield and the SB35, N-200 and Si ocra genotypes were sensitive varieties to water deficit stress. Multivariate Biplot of genotypes confirmed the results of Classification of genotypes for identifying tolerant genotypes.