EVALUATION OF DROUGHT TOLERANCE IN NEW COTTON CULTIVARS USING STRESS TOLERANCE INDICES

Drought is a wide-spread problem seriously influencing production and quality ofcotton (Gossypium hirsutum L.), but development of resistant cultivars is hamperedby the lack of effective selection criteria. The objective of this study was toevaluate the ability of several selection indices to identify drought tolerant cultivarsunder different environmental conditions. Thirteen cotton cultivars were evaluatedunder both moisture stress (2016) and non-stress (2013) field environments using arandomized complete block design for each environment. Six drought toleranceindices including stress susceptibility index (SSI), stress tolerance index (STI),tolerance index (TOL), mean productivity (MP), geometric mean productivity(GMP) and mean harmonic productivity (HMP) were used. The significant andpositive correlation of yield of genotype under non-stress condition (Yp) and MP,GMP and STI showed that these indices were more effective in identifying highyielding cultivars under different moisture conditions. The results of calculatedgain from indirect selection in moisture stress environment would improve yieldbetter than selection from non moisture stress environment. Coton breeders should,therefore, take into account the stress severity of the environment in choosing anindex. The varieties Viki and Avangard-264 had the highest yields under non-stressconditions. Vega and Chirpan-539 varieties had a low yield potential and showed ahigh stress tolerance to drought