Flavonoid Biosynthesis in Dahlia (<i>Dahlia variabilis</i>) Flowers

Dahlia (Dahlia variabilis) is a popular ornamental plant belonging to the Asteraceae family grown in many countries because of its wide variation in flower shape, size and color. Among its diverse attractive traits, flower color is one of the most important ornamental traits in dahlia. The pigments in dahlia flowers are flavonoids (anthocyanins, flavones, and 6′-deoxychalcones), and the presence and amount of these pigments determines the color of the flower. In this review, the history of research on dahlia flower color, biosynthesis of floral pigments focusing on anthocyanin biosynthesis, 6′-deoxychalcone biosynthesis and bicolor pattern formation, as well as unstable pigmentation in bicolor cultivars, are summarized. Finally, for future dahlia breeding, candidate genes determining flower colors are proposed.