Cell membrane stability- an important criterion for selection of heat tolerant genotypes in wheat (Triticum aestivum L.)

Cell membrane stability, grain filling rate, grain filling duration, canopy temperature and grain yield were used to evaluate performance of 100 diverse bread wheat (Triticum aestivum L.) genotypes under timely sown and late sown heat stress conditions for two cropping season. The genotypes differed significantly for all the traits show-ing considerable variation for improvement of characters. The genotypes WH1165 had significant high grain yield (14.6* g and 11.4g) and (11.3* g and 11.4* g) followed by cell membrane stability under timely sown and heat stress conditions, respectively indicating potential tolerance against heat stress. Correlation coefficients revealed that cell membrane stability (0.451**) and (0.639**) in timely sown and in late sown conditions, respectively were the most important trait followed by grain filling rate (0.882** and 0.744**) under timely sown and late sown conditions respec-tively. Results revealed that bread wheat genotypes which had high value of cell membrane stability had high grain yield showed potential photorespiration and high grain filling rate under heat stress condition. Twenty two genotypes WH1021, WH1155, VL803, WH787, NW1014, Raj3765, HD1869, 2042, WH1124, HD2285, WH1133, HUW234, 4066, Sonak, UP2425, UP2473, PBW503, PBW373, PBW533, SGP13, HD2643 and WH789 were identified as heat tolerant genotypes based on their relative performance in yield components, grain yield and heat susceptibility indi-ces. These genotypes were found to be ideal candidates to be used in developing heat tolerant wheat varieties. Canopy temperature, membrane thermostability and grain filling rate have also shown strong correlation with grain yield. Because of this association, these traits constitute the best available ‘tool’ for genetic improvement of wheat suitable for cultivation under heat stressed environments. Thus, these could be used as indirect selection criteria for developing heat tolerant wheat genotypes that would provide sufficient yields to meet the ever increasing wheat demand