Phenotypic diversity and Principal component analysis to associate physiological traits contributing to grain yield under moisture stress in durum wheat germplasm

Drought stress is a major abiotic constraint affecting the productivity of durum wheat ( Triticum turgidum subsp. durum ), particularly in arid and semi-arid regions. Our study evaluated 225 durum wheat germplasm lines (GDP), with five standard checks under contrasting moisture regimes to dissect physiological, morphological, and seedling traits associated with drought tolerance. The results showed significant variability for key traits, including chlorophyll content (SPAD), membrane stability index (MSI), canopy temperature (CT), root-to-shoot ratio (RSR), and grain yield. Drought stress led to pronounced reductions in grain yield (26.8%), seedling vigor (up to 57.3%), and membrane stability (24.8%), while increasing canopy temperature and RSR. Correlation analysis revealed strong positive associations between grain yield and SPAD, MSI, and seedling vigor under stress, while PCA identified these traits as major contributors to drought adaptation. Hierarchical clustering and principal component analysis enabled the identification of divergent genotypic groups and high-performing lines, notably UASDWG_246, UASDWG_216 and UASDWG_299, which consistently exhibited superior performance across both seedling and reproductive stages. These results highlight the value of integrating multistage phenotyping and multivariate analyses for improving drought resilience in durum wheat breeding programs.