Response of upland cotton (<Emphasis Type="Italic">G.hirsutum</Emphasis> L.) genotypes to drought stress using drought tolerance indices

Drought tolerance as such is often not considered to be an independent trait by plant breeders. The objective of this study was to evaluate eight drought tolerance indices, namely stress susceptibility index (SSI), yield stability index (YSI), yield reduction ratio (Yr), yield index (YI), tolerance index (TOL), mean productivity (MP), geometric mean productivity (GMP), and stress tolerance index (STI) in upland cotton (G. hirsutum L.) genotypes. For this purpose, 16 genotypes were sampled during the 2013-2014 growing seasons under both normal and drought-stress field conditions at the Main Cotton Research Station of Navsari Agricultural University, Surat, India. The drought tolerance indices were calculated based on seed cotton yield under drought stress and non-stress conditions. Mean comparison of drought tolerance indices and seed cotton yield validated the significant influences of drought stress on yield as well as significant differences among genotypes. Results of calculated correlation coefficients and multivariate analyses showed that GMP, MP and STI indices were able to discriminate drought-sensitive and tolerant genotypes. Cluster analysis using the drought-tolerance indices divided the 16 genotypes into tolerant and susceptible groups. Two genotypes, G.Cot.16 × H-1353/10 and H-1353/10 × G.Cot.16 gave good yield response under drought conditions leading to their stability during water stress conditions. Based on multivariate analyses using the indices individually or in combinations, it was possible to identify the most yield-stable genotypes across the environments. Overall, we concluded that GMP, MP and STI indices can be efficiently exploited not only for screening drought tolerance but also to identify superior genotypessuitable for both stress and non-stress field conditions.