Evaluation of wheat genotypes for terminal heat tolerance by simple physiological traits

Four wheat genotypes were evaluated for terminal drought and heat tolerance by imposing three irrigation levels under timely and late planting. The physiological traits such as leaf relative water content (RWC), canopy temperature depression (CTD) and relative injury to cell membrane (RI) were measured during the reproductive growth period before and after desiccant spray (KI, potassium iodide) along with the grain yield and yield-attributes recorded after physiological maturity. RWC and CTD decreased while RI increased significantly in late planted crop. RWC and CTD were higher in irrigated (I_N) and I_N+KI spray than unirrigated environment (I₀). Grain yield was higher under timely than late sown condition and in irrigated than unirrigated and I_N+KI environments. Genotype PBW 343 showed higher RWC, CTD and grain yield than genotypes NIAW 34, Raj 3765 and WH 711. RWC and CTD showed positive while RI showed negative association with grain yield. RWC, CTD and RI were also correlated with each other. Therefore, these traits can be successfully used to screen wheat genotypes for terminal drought and high temperature stress caused by late planting.