Evaluation of Nepalese wheat genotypes for grain yield under drought stress: a trait-based analysis

Drought stress increasingly threatens wheat production, particularly in South Asian countries, underscoring the need for drought-tolerant varieties. This study evaluated 20 Nepalese wheat genotypes under irrigated and drought conditions to identify key yield-attributing traits and promising parental lines for climate-resilient breeding. Drought stress significantly (p < 0.01) reduced all observed yield-attributing traits, resulting in an 86.49% reduction in mean grain yield. High to moderate heritability and genetic advance estimates for days to booting (DTB), days to heading (DTH), spike length (SL), net spike per meter square (NSPMS), number of spikelets per spike (NSPS), and thousand grain weight (TGW) indicated their strong potential for genetic improvement. Under drought conditions, grain yield showed significant positive correlations (p < 0.05) with plant height (Ph) (r = 0.4711), SL (r = 0.3746), NSPS (r = 0.3697), NGPS (r = 0.4749), net spike weight (NSW) (r = 0.5477), and TGW (r = 0.3801). This implies that genotypes having taller height with longer spikes, higher spikelet and grain number, and heavier grains tend to sustain higher yield under drought stress. In line with these trait–yield relationships, cluster heat map analysis identified G10 (NL 1488), G9 (NL 1492), G17 (RR21), G11 (NL 1447), G1 (BL 5106), and G4 (Bhrikuti) as promising parental lines. Overall, the study establishes a clear trait-based selection framework for improving drought resilience in wheat and provides a strong empirical basis for integrating field phenotyping with molecular breeding approaches.