The putative parents of the Hirado azalea (Rhododendron × pulchrum) are R. scabrum, R. ripense, R. × mucronatum, and other related cultivars. Hirado azalea shows a wide range of flower color variation, but the genetic basis for this color variation is not well understood. In this study, we investigated the anthocyanin pathway gene, flavonoid 3', 5' hydroxylase (F3'5'H), by genomic DNA analysis, cDNA sequence analysis, and deduced amino acid sequences to assess the genetic relationships between these taxa, as well as investigating the genetic basis of color variation in this group. In R. scabrum and red and pink flowered Hirado azalea cultivars, in which delphinidin (Dp) derivatives are absent, only the exon 2 region was amplified using specific primers in a coding region (CDS) of the F3'5'H gene, except for exon 1, suggesting that the DNA structure of exon 1 is defective in these plants that lack Dp derivatives. On the other hand, R. ripense, R. macrosepalum, and R. yedoense var. poukhanense and R. × mucronatum ‘Shiro-ryūkyū’, with Dp derivatives have normal F3'5'H DNA gene structure. The lengths of the F3'5'H cDNA nucleotide sequences of these wild species were 1533 bp (510 AA), whereas in R. × mucronatum ‘Shiro-ryūkyū’, two different sequence lengths were observed—1533 and 1551 bp (510 and 516 AA). R. ripense, R. × mucronatum ‘Shiro-ryūkyū’, and four purple and white flowered Hirado azalea cultivars were grouped in the same cluster in the F3'5'H gene phylogeny. Among the four Hirado azalea cultivars, the lengths of F3'5'H in CDS were 1551 bp, which included a 5 bp insertion adjacent to the stop codon in ‘Ademurasaki’ and ‘Hakuhō’. However, ‘Hirado-no-homare’ and ‘Shirokujyaku’ lacked this insertion and had 1533 bp CDS. When PCR was performed to distinguish the 5 bp insertion, the amplified product was found in some R. ripense individuals and R. × mucronatum ‘Shiro-ryūkyū’, but not in R. scabrum or R. macrosepalum. These results suggest that the wide range of flower color in Hirado azalea cultivars is caused by variation in the F3'5'H genotype derived from hybridization between R. scabrum and either R. ripense or R. × mucronatum ‘Shiro-ryūkyū’.

的平户杜鹃花（的推定父母杜鹃× pulchrum）是R. scabrum，R. ripense，R. × mucronatum，以及其他相关的栽培品种。平户杜鹃花显示出广泛的花朵颜色变化，但是这种颜色变化的遗传基础尚不十分清楚。在这项研究中，我们通过基因组DNA分析，cDNA序列分析和推导的氨基酸序列，研究了花色苷途径基因黄酮3'，5'羟化酶（F3'5'H），以评估这些类群之间的遗传关系。以及调查该组中颜色变化的遗传基础。在R. scabrum中以及没有粉色和粉红色花朵的平户杜鹃花品种，其中不存在delphinidin（Dp）衍生物，仅使用第3外显子1的F3'5'H基因编码区（CDS）中的特异引物扩增了第2外显子区域。提示在缺少Dp衍生物的这些植物中外显子1的DNA结构存在缺陷。在另一方面，R. ripense，R. macrosepalum和R. yedoense变种。具有Dp衍生物的poukhanense和R. × mucronatum'Shiro -ryūkyū'具有正常的F3'5'H DNA基因结构。这些野生物种的F3'5'H cDNA核苷酸序列的长度为1533 bp（510 AA），而在R. × mucronatum中“Shiro-ryūkyū”，观察到两个不同的序列长度-1533和1551 bp（510和516 AA）。R. ripense，R。 × mucronatum'Shiro -ryūkyū'和四个紫色和白色的平户杜鹃花品种在F3'5'H基因系统发育中分组在同一簇中。在四个平户杜鹃花品种中，CDS中F3'5'H的长度为1551 bp，其中包括在'Ademurasaki'和'Hakuhō'中与终止密码子相邻的5 bp插入。然而，“ Hirado-no-homare”和“ Shirokujyaku”缺少该插入，并且具有1533bp的CDS。当进行PCR区分5 bp插入时，在一些R. ripense个体和R. × mucronatum中发现了扩增产物。'Shiro-ryūkyū'，但不在R. scabrum或R. macrosepalum中。这些结果表明，平花杜鹃花品种的花色范围宽广是由于R. scabrum和R. ripense或R. × mucronatum'Shiro -ryūkyū'杂交产生的F3'5'H基因型的变异引起的。