Assessment of terminal heat stress on yield and grain parameter in wheat

Screening of wheat entries for terminal heat tolerance can be performed using yield performance along with various grain parameters including grain area, grain length, grain width, grain diameter, and grain perimeter. In the present study, adverse effect of terminal heat stress on grains was quantified by measuring yield and grain parameters of diverse and selected wheat genotypes under staggered sowing environments for three consecutive years. In the first year, 100 diverse genotypes were screened under timely and late sown conditions for yield and grain parameters. This study suggested a further preliminary yield trial of the shortlisted 21 genotypes under late-sown. This study resulted in six promising genotypes for further evaluation in three distinct sowing environments. A few entries express potential to perform well in late sown along with timely-sown ecologies due to non-significant variation in grain parameters namely grain length, grain width and grain diameter. The correlation coefficient varied from positive to negative and vice versa across different sowing environments. However, yield per plot (YPPT) showed a positive significant association with grain perimeter (0.28** & 0.9**), grain diameter (min) (0.24* & 0.86**) and grain area (0.34** & 0.81**) under late sown in 2021–22 & 2023–24, respectively. Overall, 21.91% reduction in YPPT was evident under LS. Regression analysis confirmed that grain area, grain diameter and grain width positively impacted yield under late sown. These grain parameters can be promoted as selection criteria for screening of terminal heat-tolerant wheat. Two promising entries namely 46 (GID:7631433; BRW3989) and 92 (GID:8247009; BRW3992) were considered donor for heat-tolerant and developing segregating families using them are under process.