Genetic Analyses of Grain Yield and Yield-attributing Traits in Wheat (Triticum aestivum L.) Grown under Terminal Heat Stress

Abstract

Terminal heat stress is a key constraint in wheat cultivation and its impact is anticipated to increase in the current context of climate change. Heat stress poses a serious threat, especially during the reproductive and grain-filling stages in wheat that can causes a significant reduction in yield. The current research was carried out to assess the nature of genetic variability and the relationship between yield and yield attributing traits of 30 different wheat genotypes grown under terminal heat stress and also to isolate the best performing genotypes based on stress tolerance indices. The highest estimates of Phenotypic Coefficient of Variation (PCV) and Genotypic Coefficient of Variation (GCV) were observed for plant height 67 and 65, respectively. Most of the traits showed high heritability, among which days to germination (98.45%), plant height (96.51%), total grain per plant (99.71%) exhibited the highest. The highest genetic advance was estimated in filled spikelet per spike (97.37%). Total grain weight and hundred grain weight had strong positive correlation with yield per plant. The characters viz., plant height, chlorophyll content, no. of tiller per plant, days to 50% flowering, filled grain, hundred grain weight, flag leaf length, days to booting, total grain weight had a positive direct effect on grain yield. In this experiment, SADH-2, DSN-76, NK-5, NE-3, SA-2 had the lowest value of Tolerance Index (TOL) which indicated that they had high tolerance towards heat stress. The highest value of Yield Stability Index (YSI) was observed in DSN-76, NE-3, BAW 1008, NK-5, SADH-22 which indicated that they had lower yield reduction and higher yield stability under heat stress. The optimum sowing date showed better performance for all the examined traits compare to heat stress condition. The identified genotypes hold promise for future breeding programs aimed at developing wheat varieties resilient to terminal heat stress.