Genetic and phenotypic characterization of seedling drought tolerance in wheat with integrated analysis of trait variation and QTL mapping.

Wheat (Triticum aestivum L.) is a staple cereal crop highly vulnerable to drought stress, particularly during early seedling establishment, which limits productivity and yield stability. This study evaluated a recombinant inbred line population under well-watered and drought environments to dissect the morphological, physiological, and genetic bases of seedling drought tolerance. Drought stress severely reduced shoot and leaf biomass, while paradoxically enhancing root growth, suggesting adaptive resource reallocation to improve water foraging. Genetic variance analyses uncovered increased heritable variation for root traits under stress, alongside significant genotype-by-environment interactions, indicative of distinct adaptive responses. Multivariate analyses revealed an integrated stress-response network linking stay-gFreen phenotypes and biomass maintenance. Importantly, QTL mapping identified twelve drought-specific loci most notably on chromosomes 2A, 3B, 5A, and 6A as well as eight loci unique to non-stress conditions, underscoring environment-dependent genetic architectures. Major QTLs affecting seedling length, root length, and leaf senescence offer promising targets for marker-assisted breeding. Collectively, these results illuminate the complex, multigenic control of early-stage drought tolerance in wheat, providing a robust foundation for developing cultivars with improved resilience in water-limited environments and strengthening climate-smart breeding pipelines.