Daminozide reduces red color intensity in herbaceous peony (Paeonia lactiflora Pall.) flowers by inhibiting the expression of flavonoid biosynthetic genes.

Daminozide is a plant growth retardant that inhibits 2-oxoglutarate-dependent dioxygenase activity in the gibberellin biosynthesis pathway, but few studies have focused on its effect on the flavonoid biosynthesis pathway involved in flower color. In the present study, the effect of daminozide on the regulation of flower color was investigated. An herbaceous peony (Paeonia lactiflora Pall.) cultivar 'Fenzhu Pan' was used as the material and treated with daminozide. Color parameters of petals were measured; flavonoid composition and content as well as flavonoid biosynthetic gene expression were monitored. The results showed that daminozide treatment caused less red coloration in herbaceous peony. The content of total anthocyanins was decreased by 23%, and the content of total anthoxanthins was increased by 8%; thus, it appeared that less red coloration in daminozide-treated flowers was associated with restricted anthocyanin accumulation. Furthermore, the gene expression patterns of flavonoid 3'-hydroxylase, dihydroflavonol 4-reductase and anthocyanidin synthase were lower after daminozide treatment, which could decrease anthocyanin accumulation and lead to less red coloration in flowers. These findings would improve our understanding of daminozide regulation of flower color in herbaceous peony.