Integrated Evaluation of Agronomic and Phytochemical Traits in Red Clover (Trifolium pratense L.) for Dual-Purpose Breeding

Red clover (Trifolium pratense L.) is an important forage legume that is also a valuable source of bioactive compounds with potential health-promoting properties. This study evaluated the variability among diploid (2n) and tetraploid (4n) red clover cultivars in forage productivity, quality-related parameters, polyphenol and flavonoid content, and antioxidant activity, in order to identify promising ideotypes for dual-purpose breeding. A total of 90 cultivars were assessed under field conditions; green matter yield, dry matter yield, crude protein content, and protein yield were analyzed together with total polyphenols, total flavonoids, and antioxidant activity. Spearman correlation and principal component analysis (PCA) were used to relate the traits and identify cultivars with contrasting characteristics. Cultivar differentiation was pronounced within each ploidy group, whereas diploid and tetraploid cultivars overlapped substantially in the multivariate space, indicating that ploidy alone is not a reliable predictor of forage or medicinal value. At the group level, tetraploids tended toward higher biomass, protein-related traits, and total polyphenol concentration, while total flavonoids and antioxidant activity were broadly comparable between groups. Forage- and medicinal-related traits were only weakly correlated and thus behaved as largely independent selection targets—which is precisely why integrated multi-trait evaluation is required to identify cultivars combining both. Several cultivars did combine favorable agronomic and phytochemical characteristics, supporting within-group selection of red clover germplasm with dual forage and medicinal potential for sustainable agricultural systems.