Variation in Forage Yield-Related Traits in a Broad Range of Sainfoin Accessions

Sainfoin (Onobrychis spp.) is a perennial legume forage crop valued for its adaptation to dry environments, nitrogen fixation capacity, and ecosystem service benefits. Despite its agronomic importance, broad comparative evaluations of cultivated sainfoin germplasm across environments remain limited. In this study, a diverse global panel of cultivated sainfoin germplasm representing O. arenaria, O. transcaucasica and O. viciifolia was evaluated in replicated field trials in Tekirdağ, Türkiye and Salina, Kansas, USA. Significant environmental, species, and accession effects were detected for numerous agronomic and forage-related traits, indicating substantial phenotypic diversity and strong environmental responsiveness across the evaluated germplasm. Several vegetative and forage-related traits, including stem length, forage dry matter, and canopy height, exhibited moderate to relatively high entry-mean repeatability across environments. Correlation analyses revealed strong positive associations between stem morphology traits and forage biomass production, suggesting that vegetative architecture traits may serve as useful indirect selection criteria for forage improvement. Principal Component Analysis revealed substantial phenotypic overlap among cultivated sainfoin taxa, indicating that the evaluated agronomic traits alone did not clearly separate species groups. Several plant introduction accessions performed comparably to or exceeded commercial cultivars for forage-related traits, highlighting the value of broad germplasm collections for sainfoin improvement. Collectively, these findings demonstrate that cultivated sainfoin germplasm contains substantial breeding-relevant diversity and support continued multi-environment evaluation and regionally adapted breeding strategies for perennial forage improvement.