Petal Color Is Associated with Leaf Flavonoid Accumulation in a Labile Bicolor Flowering Dahlia (<i>Dahlia variabilis</i>) ‘Yuino’

Abstract

Bicolor flowering dahlias generally produce inflorescences with bicolor petals characterized by a colored basal part and a white tip; however, they frequently produce single-colored petals. This petal color lability prevents uniform production of cut or pot flowers of bicolor dahlias and reduces the economic value of bicolor cultivars. In this study, to reveal the underlying mechanism and control color lability, the pattern of occurrence of singlecolored petals was characterized in a red-white bicolor flowering cultivar 'Yuino'. 'Yuino' produced inflorescences with bicolor petals, red petals, and both red and bicolor petals. Red petals occurred almost always at the outer whorls or sectorally in a mixed inflorescence, similar to a chimera or a lateral mutant. The occurrence of red petals was higher in field experiments during May to December than in greenhouse experiments during October to next July. We identified the "R-line" plant, which produced red petals with high frequency during the winter to spring cultivation; this characteristic to produce red petals with high frequency was retained through vegetative propagation. There were strong relationships between inflorescence color and leaf phenotype; red petal-producing plants accumulated flavonoids in leaves, whereas only bicolor petal-producing plants tended not to accumulate flavonoid in leaves. This suggests that petal color of 'Yuino' is associated with flavonoid synthetic potential in shoot. Therefore, a phenotypic difference is observed not only in petal colors but also at the whole plant level.

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

“…In our previous report (Ohno et al, 2016), 'Yuino' leaves were classified into two types: flavonoid-rich leaves and flavonoid-poor leaves, and a relationship between petal colors and leaf flavonoid accumulation was evident, namely red petal-producing individuals accumulated flavonoids in leaves, whereas only bicolor petal-producing individuals tended not to accumulate them in leaves. At that time, the flavonoids in the leaves of 'Yuino' were presumed to be chalcone-like compounds using photodiode array analysis.…”

“…The freeze-dried leaves of 'Yuino' R-line (Ohno et al, 2016) (80 g) were immersed in methanol-water (1:1, v/v) (5 L) at room temperature for 1 day and extracted. A-L shown in Figure 1A were isolated and purified by paper chromatography (PC) and a Sephadex TM LH-20 (GE Healthcare Japan, Tokyo, Japan) column (35 × 300 mm) chromatography (CC).…”

“…The cuttings of 'Yuino' were grown in the experimental field or greenhouse at Kyoto University (Kyoto, Japan). For NMR analysis, the leaves of the 'Yuino' R-line, which tend to produce red petals and to accumulate flavonoids in leaves with high frequency, retaining this characteristic through vegetative propagation (Ohno et al, 2016), were used.…”

Post-transcriptional silencing of chalcone synthase is involved in phenotypic lability in petals and leaves of bicolor dahlia (Dahlia variabilis) ‘Yuino’

“…Bicolor dahlias can bloom inflorescences with only bicolor petals, only single-colored petals, or a mixture of the two. In a mixed inflorescence, the single-colored petals are located in the outer whorls or sectorally in many cases (Ohno et al 2016), making it unlikely that this phenomenon can be explained by a mutation in particular genes. This petal color lability in bicolor dahlias attracted much research in the 1930s (Lawrence 1931;Tammes and Groeneveld-Huisman 1939) and yet the mechanism(s) underlying it remain unknown.…”

“…1). Based on the observation that these red petals occur sectorally in an inflorescence (Ohno et al 2016), it was assumed that whatever phenomenon controls their production occurs meristematically. There were two types of leaves, one was flavonoid-rich leaves and the other was flavonoid-poor leaves.…”