Utilizing the endangered yellow species <i>Delphinium luteum</i> to create novel flower colours via interspecific hybridization

Abstract Delphinium luteum is an endangered species characterized by unique yellow flowers. Although its utilization in breeding has historically been limited, it possesses valuable genetic traits. In this study, we performed interspecific hybridization between the orange-red flowered D. nudicaule and D. luteum to create novel flower colours and analyze pigment inheritance. The crossing of genetically fixed hybrid lines resulted in progenies segregating for red-purple, red, orange and yellow flowers. Notably, red-purple flowers, a novel trait absent in both parents, were produced. LC-MS/MS analysis revealed that these red-purple flowers accumulated complex anthocyanins derived from pelargonidin, cyanidin and delphinidin, whereas D. nudicaule contained only pelargonidin-based anthocyanins. This suggests that D. luteum complemented the flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylase genes that are non-functional in D. nudicaule . Conversely, yellow progenies accumulated no anthocyanins, suggesting a pigmentation phenotype similar to D. luteum . These results demonstrate that D. luteum is a promising genetic resource for introducing novel flower colours and expanding the phenotypic diversity of Delphinium through traditional breeding.