Identification of Flavonoids in Leaves of a Labile Bicolor Flowering Dahlia (Dahlia variabilis) ‘Yuino’

Abstract

Bicolor flowering dahlias are a group of cultivars that produce inflorescences with bicolored petals characterized by a colored basal part and a white tip. However, they frequently produce single-colored petals, even if they are vegetatively propagated. In a previous study, strong relationships between inflorescence color and leaf phenotype were observed in a red–white bicolor flowering dahlia ‘Yuino’; red petal-producing individuals accumulate flavonoids in leaves, whereas only bicolor petal-producing individuals tend not to accumulate them in leaves. Flavonoids in leaves are assumed to be chalcones. In this study, we investigated flavonoids in the leaves of ‘Yuino’ by nuclear magnetic resonance analysis and identified six caffeoyl esters, four flavonol derivatives, and three novel butein derivatives in the flavonoid-rich leaves of ‘Yuino’. The three novel compounds were butein 4',4-O-di-[2-O-(β-glucopyranosyl)-β-glucopyranoside], butein 4'-O-[2-O-(β-glucopyranosyl)-β-glucopyranoside]-4-O-β-glucopyranoside, and butein 4'-[6-O-(3-hydroxy-3-methylglutaryl)-β-glucopyranoside]-4-O-β-glucopyranoside. On the other hand, only caffeoyl esters were detected in flavonoid-poor leaves. These data demonstrated that flavonoid-rich leaves accumulated the flavonoids of butein and flavonol derivatives. The common enzyme for the biosynthesis of butein and flavonol derivatives is chalcone synthase; thus, the importance of chalcone synthase for phenotypic lability in ‘Yuino’ was confirmed.