Effect of heat stress on crop phenology, yield and seed quality attributes of wheat (Triticumaestivum L.)

High temperature is a major determinant of wheat development and growth and causes yield loss in many regions of the world. The present study was aimed at assessing the effects of heat stress on phenologic, floral, yield and seed quality attributes of fourteen wheat genotypes under four environmental conditions; raised at two dates: November (favourable) and January (heat stress) during rabi seasons of 2012-13 and 2013-14. Under heat stress condition, 5-12 degrees C higher temperatures were recorded at anthesis and post-anthesis stage than the normal sown. The study revealed significant differences among dates of sowing, thereby indicating sensitivity to heat stress. Among the plant morphological traits, there was a maximum reduction in plant height under heat stress condition (January sown) as compared to normal sown condition.Phenology of wheat crop was also significantly affected by higher temperature: Wheat varieties sown during the month of November took more time to reach maturity while late sown material recorded lesser crop growth duration. Among the seed yield and quality parameters, high temperature caused-maximum reduction in tiller number (70%) followed by grain yield (67.3%. reduction), 1000-grain weight (47% reduction) and vigour Index II (52.7% reduction). Hence, these traits were identified as the most susceptible traits to heat stress. Heat stress also caused a reduction-of 39.7 per cent for or canopy temperature depression at grain filling stage. Flag leaf area, spikelet fertility and pollen fertility reduced by 33.1%, 22.7% and 7.7%, respectively, thereby indicating that these traits were less affected due to higher temperature.Genotypes GW 366 and HD 2888 showed least heat susceptibility index (HSI)for grain yield whereas for seed quality, HD 3093 showed better tolerance compared to Others.