The high temperature during crop growing seasons is prevalent in the Indo-Gangetic region, causing heat stress to the plants. Heat stress in wheat is a threat to food security and agricultural sustainability. Finding a heat-stress stable wheat genotype is a timely demand. A field study scrutinized 60 genotypes, designed with five different sowing dates, each with 10-day intervals, to identify the stable one. All the growth parameters showed significant responses to terminal heat stress effects. Wheat yield declined by 20%–57% with the successive heat-stress increases with late sowing dates. Most plant growth parameters had a similar or slight variation in genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV). The higher PCV in pollen sterility, chlorophyll content, and the number of filled grains than GCV indicates environmental influence on the expression of the characters studied. These parameters also showed a direct positive effect on crop yield when analyzed in their path coefficients. Genotype performance in yield incurred heat-stress tolerance index tests and revealed that Sourav, Gourav, SA-8, Chyria 3, CB-47, and Sabia genotypes had suitable tolerance, stress-susceptibility, and high-yield stability indexes, indicating higher yields in stress condition. AMMI analysis also showed a significant variation, and the genotypes SA-8, Chyria 3, Pavan, DSN-117, and Sonalika were the most stable. The most unstable genotypes were SA-2, Kheri, and FYN-PVN. The genotypes SA-8, Chyria 3, Pavan, DSN-117, and Sonalika can benefit further breeding as sources of genetic material to develop heat-tolerant, high-yielding wheat varieties.

Keywords: Wheat, heat stress, heat tolerance indices, stability model (AMMI), stable genotypes

Key findings: Heat stress significantly affected all the yield-contributing parameters, causing yield reduction at late sown dates by 20%–57% than the optimum planting date. Yield-contributing parameters which had high heritability also influenced environmentally, among the 60 genotypes of wheat SA-8, Chyria 3, Pavan, DSN-117 and Sonalika showing stable performance under different heat-stress conditions, opposite to the SA-2 genotype. The selected materials can further benefit as source materials to develop heat-tolerant, high-yielding wheat varieties.