Chemical Mechanism of Flower Color Microvariation in Paeonia with Yellow Flowers

Paeonia species are important ornamental plants, including three types: tree peony, herbaceous peony, and Itoh hybrid peony. Paeonia with yellow color is desired and becoming popular. However, the chemical mechanism of the formation of yellow flowers in Paeonia is still unclear. In this study, 14 representative samples were selected: four samples of three species of Paeonia, four herbaceous peony cultivars, three lutea hybrid tree peony cultivars, and three Itoh hybrid peony cultivars. The petal extracts of the samples were determined by HPLC-DAD and HPLCQ-TOF-MS/MS. In total, 29 flavonoids were isolated and identified, including 28 flavonol glycosides and one chalcone derivative. There were significant differences in the composition and content of flavonoids in petals of different cultivars (species). The total content of flavonoids was between 19.430 and 143.043 mg.g(-1) DW. Flavonol glycosides were detected in all samples. Chalconaringenin 2'-O-glucoside was detected from one herbaceous peony cultivar 'Golden Wheel' lutea hybrid tree peony cultivars, and Itoh peony cultivars. The content of chalconaringenin 2'-O-glucoside in the samples was more than 43% of total flavonoids. The pigment type and content of lutea hybrid tree peonies and Itoh hybrid peonies are similar. Total flavonoids, especially quercetin 3-O-galloylglucoside and chalconaringenin 2'-O-glucoside contribute greatly to the formation of yellow flowers of Paeonia. The results of this study provide a comprehensive understanding of the chemical mechanism for yellow flower coloration of Paeonia, and lay the foundation for yellow flower breeding of Paeonia