Revealing Genetic Diversity and Drought Tolerance in Durum Wheat through Agro-Physiological and Molecular Approaches

Under changing climate conditions, evaluating both genetic and environmental factors is essential for crop improvement. Limitations of conventional breeding have increased the use of molecular markers to obtain precise genotypic information and improve selection efficiency. This study evaluated drought tolerance in 15 durum wheat genotypes across two cropping seasons under rainfed and irrigated conditions. A randomized complete block design with four replications was used to assess agro-physiological traits, quality parameters, drought tolerance indices, and molecular diversity using iPBS and SCoT markers. Significant genotypic variation was observed for grain yield, 1000-kernel weight, hectoliter weight, protein and starch content, and color traits under both conditions. Ovidio had the highest grain yield and starch content, while Seckin 21 showed the highest 1000-kernel weight. Drought tolerance indices identified NZFM-41 and Maestrale as the most drought-resilient, and Ovidio as highly adaptable with stable yield. 12 indices (SSI, TOL, MP, GMP, STI, YI, YSI, HM, SDI, DI, RDI, SSPI) were calculated from yields under stress (Ys) and nonstress (Yp) conditions. Molecular analysis with 14 iPBS and 10 SCoT primers showed greater polymorphism and allelic diversity for iPBS (PIC = 0.287, Nei's distance = 0.5348) than SCoT (PIC = 0.191, Nei's distance = 0.2700). Clustering and population structure revealed two subpopulations, with iPBS providing higher resolution (FST = 0.3443). MP, GMP, STI, YI, HM, and DI were the most reliable indices for identifying drought-tolerant genotypes. In conclusion, iPBS markers exhibited higher discriminatory power than SCoT for assessing genetic diversity, while specific indices (MP, GMP, and STI) proved most effective for identifying drought-tolerant durum wheat genotypes, with NZFM-41 and Maestrale emerging as promising genetic resources for breeding programs aimed at enhancing climate resilience.