Yield and Agronomic Performance of Nepalese Wheat Genotypes Under Irrigated, Heat Stress, and Rainfed Environments

Understanding genotypic variation in wheat under multiple abiotic stresses is critical for sustaining productivity under climate changing scenarios. The study evaluated twenty elite Triticum aestivum L. genotypes, including three commercial checks (Bhrikuti, Gautam, and RR-21), under irrigated, heat-stress, and rainfed environments in the Terai region of Nepal at two different sites during the 2024–25 wheat growing season. Mean grain yield declined by 28.8% under heat stress and 67.4% under a rainfed environment compared to irrigated environments. The yield reductions were associated with significant genotypic variation (p<0.001) observed across environments for plant height, spikes per square meter, grains per spike, thousand kernel weight, and days to maturity. To identify resilient germplasms, eleven stress tolerance indices were evaluated. Mean stable yield (MSY), harmonic mean productivity (HMP), and modified stress tolerance index 2 (MSTI2) showed the strongest association with grain yield under both stress environments, while modified stress tolerance index 1 (MSTI1) and mean productivity (MP) were most effective under a nonstress environment. Bhrikuti, NL 1504, NL 1506, and NL 1718 demonstrated superior tolerance across both stress environments. Therefore, these identified genotypes could serve as valuable donor parents for developing stress-resilient varieties. These findings provide a robust quantitative framework for selecting indices and genotypes to enhance wheat productivity and ensure food security amidst escalating climatic variability in South Asia.