Capturing the Variability for Heat and Drought Tolerance in Wheat Using Multiple Selection Indices

Experiments were conducted to quantify the effects of individual heat, drought and combined heat and drought stress on wheat yield and its component traits as well as to identify suitable traits and stress selection indices for selecting tolerant genotypes. A total of 91 wheat genotypes were evaluated for tolerance to both stresses for two consecutive years. Significant differences were observed among genotypes for all traits under all environments, suggesting wide genetic variability. The most affected traits were grain yield and biological yield under individual heat and drought as well as under combined stress. Grain filling duration (GFD) and grain filling rate were the key contributors towards tolerance. Selection indices viz. stress tolerance index, mean relative performance and yield stability index were positively and significantly correlated with grain yield, days to maturity, grain filling duration, grain filling rate, and other key yield contributing traits under normal and stress environments. Genotype DBW187 was identified to be tolerant to both heat and drought stresses, genotype WH730 was tolerant under combined heat and drought stress, DBW273 and DBW173 under individual heat and PBW780 and PBW765 under individual drought stress based on combined ranking of indices. These genotypes could be used to develop genotypes tolerant to heat and drought stress, and to promote high grain yield.