WHEAT GENOTYPES RESPONSE TO HEAT STRESS TOLERANCE NORMAL AND DELAY SOWING DATES

Abstract

In the scenario of increasing global warming, heat stress attained greater importance. Unfortunately, Pakistan is also in the queue of the most heat-affected country. In this regard, wheat is the most important staple crop in Pakistan which is highly affected by heat stress. In this context, the genotype of wheat was evaluated at 2 sowing dates. Normal planting on 25 November and delay planting on 25 December 2015 were considered as normal and summer stress conditions, respectively. Significant differences between genotypes in normal and high temperatures indicating the suitability of the experiment to improve bread wheat genotype for heat tolerance. A decrease in various traits was noted due to delay planting indicating a visible effect of high temperature on physico-yield traits. At average physical maturity, flag leaf area, specific flag leaf weight, grain spike-1, grain weight spike-1, 1000-grain weight, grain yield plant-1, organic yield plant-1, crop index, relative water content and cell membrane stability showed a decrease of 7.01, 31.38, 20.63, 20.50, 37.93, 30.63, 37.87, 31.62, 9.38, 16.95 and 10.96%, respectively, under heat stress conditions.While the wheat genotypes like Imdad-05, NIA-Sarang and TD-1 showed minimum reductions under heat stress conditions for various traits suggesting their heat tolerance, nonetheless cultivars Khirman and AS-2002 expressed maximum declines under heat stress expressing their susceptibility to heat stress conditions. The remaining genotypes were moderately heated stress-tolerant. Key words: Delay sowing, Genotypes response, Heat stress, Normal sowing, Wheat