ABSTRACT
Delayed harvesting of rice forced late sowing of wheat particularly in IndoGangetic plain that causes severe yield penalty due to terminal heat stress. Terminal heat causes series of changes in plant system in term of physiology, growth, and yield. Various studies have indicated that the average 224maximum temperature more than 32°C during reproductive phase negatively influenced wheat grain yield and average yield loss upto 30% was reported. Physiological and biochemical traits like relative water content (RWC), membrane stability index (MSI), photosynthetic rate, chlorophyll content, various osmolytes, anti-oxidants, and some molecular chaperones (HSPs) showed variations under high temperature condition. Moreover, genotypic variation is obvious in all traits regarding thermal susceptibility. Stay green and canopy temperature depression has been found to be significant co-relation with grain yield. Terminal heat stress led to reduced grain filling duration, thousand-grain weight, grain number per year, and ultimately final yield. Furthermore, elevated temperature driven interruption in the transport of photosynthate from green foliage (source) to anther tissues (sink) leads to high pollen mortality and thereby decreases grain yield. Some wheat genotypes like NW (1014). Halna, Raj (3765). WH760, GW273 and HD2987 has been found to be suitable for late sown terminal heat stress condition and produce optimum yield.
