Assessment of terminal heat tolerance based on agro-morphological and stress selection indices in wheat

A study was conducted to quantify the effects of terminal heat stress on yield and component traits for two consecutive years under normal and late sown environments. Analysis of variance indicated significant differences among genotypes for most of the studied traits. Tiller/meter (T/M) and grain yield were the most affected traits (>30% reduction), whereas traits like grain filling rate (GFR), grain number per spike (GNPS) and thousand kernel weight (TKW) were less affected (<15%) under heat stress. The traits, viz. GFR, GNPS, TKW, T/M and spike weight, as well as the relative change in these traits exhibited positive and significant correlation with yield and yield stability index (YSI), while negative and significant correlation with heat susceptibility index (HSI) and kernel weight reduction percentage (KWR) under heat stress. Based on HSI, KWR, and YSI indices, genotypes WH 1021, NW 1014 and NW 2036 were identified as the heat tolerant, while HD 3086, HD 2967 and HD 3059 were identified to be highly productive under both normal and heat stress environments based on STI and mean yield across the environments. The above selected genotypes also showed high mean performance for GFR and TKW under heat stress and could be used for breeding wheat genotypes for heat tolerance.