Analyses of Pigment Compositions and Anthocyanin Biosynthesis Gene Expression in Hirado Azalea Cultivars

抄録

The Hirado azalea is a large flowering plant and Rhododendron scabrum, R. ripense, R. × mucronatum, and other related cultivars are considered to be its parents. In this study, we investigated the correlation of Hirado azalea cultivars with wild species and old cultivars by analyzing anthocyanidin composition patterns and the expression of anthocyanin biosynthesis genes. Hirado azalea cultivars were divided into four groups according to their pigment compositions. Hirado azalea cultivars with only cyanidin derivatives had red colored flowers similar to those of R. scabrum. Hirado azalea cultivars with both cyanidin and delphinidin derivatives as well as flavonol produced similar flower colors to those of R. ripense and R. macrosepalum. Hirado azalea cultivars with only flavonol had white colored flowers similar to those of R. mucronatum ‘Shiro-ryūkyū’. Hirado azalea cultivars with cyanidin derivatives and flavonol exhibited a wider range of flower colors compared to their parents. All samples expressed F3'H, DFR, and ANS genes, as determined by real-time quantitative RT-PCR. However, the F3'5'H gene was expressed only in samples containing delphinidin derivatives. Moreover, ‘Shiro-ryūkyū’ also expressed all four genes, as did cultivars with colored flowers, even though its flowers are white. These results suggested that the hybridization of Hirado azalea using R. scabrum as the base may produce a wide range of flower colors besides red owing to the presence of the F3'5'H gene from R. ripense, R. macrosepalum, and ‘Shiro-ryūkyū’.