Evaluation of growth and yield in wheat (Triticum aestivum L.) under heat stress conditions

High temperature stress is a major yield limiting factor in cereals. Five wheat (Triticum aestivum L.) genotypes viz.; WH 1105, PBW 550, HD 2967, PBW 621 and PBW 702 were raised under three temperature regimes (ambient+3.0^oC; ambient+3.3^oC and ambient+3.6^oC) in a temperature gradient tunnel (TGT). Crop raised at ambient temperature (outside the tunnel) was taken as control. Higher than ambient temperature accelerated plant height at vegetative stage but decreased leaf area, leaf membrane thermo-stability index (MTS), chlorophyll content. Yield and its attributes such as number of spike bearing tillers, length and compactness of spike also decreased in crop raised under TGT. Yield showed a positive correlation with MTS, chlorophyll content and compactness of spikes. The crop raised at ambient+3.6^oC temperature was adversely affected to a maximum extent among the three temperature regimes.