Effective selection criteria for assessing yield of wheat (Triticum aestivum) under early and late heat stresses in irrigated environment of South-East Asian conditions

The study was conducted for 2 winter seasons during 2004-05 and 2005-06 at Indian Agricultural Research Institute, New Delhi using 9 wheat (Triticum aiesivum L . emend. Fiori & Paol.) genotypes ('HD 2923', 'RS 91 1 ', 'HD 2944', 'HD 29501, 'HD 2936', 'RS 937', 'PBW 343', 'HD 285 1' and 'HDR 77') and 3 sowing dates (15 October, 15 November and 15 December) to assess the relative efficiency of different selection parameters. Grain yield was significantly correlated with biomass (0.8067), grains/m2(0.5387), spikes/m2 (0.661 8), grain growth rate (0.9133), biomass growth rate (0.7736) and harvest index (0.9309). The results suggest that these traits can be utilized as selection criteria for early and late heat stress. Among the different stress parameters, stress tolerance index (I-0=. 7303) followed by stress susceptibility index (I= 0.8393) was found to be the best parameter to distinguish the genotypes performing well under both the stresses and non-stress environments.