Comparative physiological response of wheat genotypes under terminal heat stress.

Wheat (Triticum aestivum L.), a staple food crop, is of great commercial importance. Its production is restricted due to multiple environmental stresses. There are indications that the wheat production is consistently limited by terminal heat stress. Previous studies revealed a varied response of different wheat genotypes under heat stress conditions. Here, comparative physiological changes in wheat genotypes viz., DBW-140, Raj-3765, PBW-574, K-0-307 and HS-240 were evaluated under timely and late sown conditions in rabi season. We observed that heat stress dramatically affects chlorophyll content and leaf area index (LAI) in sensitive genotypes whereas proline and malondialdehyde (MDA) content were higher in tolerant genotypes under late sown conditions. Further, the heat susceptibility index (HIS) for 1,000-grain weight, grain weight and grain yield of wheat genotypes viz., HS 240 and K-0-307 was highest as compared with DBW 140, Raj 3765 and PBW 574 genotypes. This finding suggests that wheat genotypes are found to differ in their ability to respond to heat, thereby tolerance, which could be useful as genetic stock to develop wheat tolerant varieties in breeding programs.