Advancing Regional Adaptation and Nitrogen Stress Resilience Through Integrative Phenotyping of Watkins Wheat Landraces via Source–Sink Dynamics

Historical landrace collections, such as the Watkins Wheat Collection, harbor immense genetic diversity that holds the potential to transform our understanding of crop resilience and adaptation. This study employs a novel integrative phenotyping approach to dissect regional adaptation and nitrogen stress resilience in Watkins wheat landraces under contrasting nitrogen regimes. By leveraging a multidimensional framework, including stress indices, geographic analyses, and multivariate clustering, this work identifies 48 landraces with contrasting responses to nitrogen limitation. High-performing genotypes, such as WATDE0013 and WATDE0020, exhibited superior biomass partitioning under stress, reflecting historical adaptation to low-input agroecosystems spanning Europe, Asia, and North Africa. These findings emphasize the value of phenotypic plasticity in nitrogen use efficiency (NUE) improvement. In contrast, low-performing accessions, such as WATDE1055, highlighted vulnerabilities to nitrogen limitation, illustrating the importance of comprehensive phenotypic screening for gene-bank prioritization. Regional adaptation patterns, elucidated through geographic analyses, uncovered stress-resilient genotypes clustered in historically marginal agricultural regions, revealing adaptive traits shaped by environmental selection pressures. Principal component analysis (PCA) and hierarchical clustering delineated five distinct phenotypic groups, enhancing our understanding of evolutionary trajectories within this collection. This integrative approach transcends traditional phenotyping methods by linking phenotype, genotype, and geographic context to uncover nuanced adaptive traits. By bridging gene bank conservation with a systems-level understanding of crop evolution, this study provides actionable insights and a robust framework for breeding climate-resilient wheat varieties. These findings underscore the critical role of preserving genetic diversity in landraces to address global challenges in nitrogen stress and climate resilience.