Article ID: SZD-045
Evergreen azalea cultivars are used as ornamental shrubs and pot plants not only in Japan, but also in Western countries. These cultivars were developed from wild species native to Japan, and through selection and crossing, cultivar groups such as the Ryūkyū-tsutsuji, Hirado-tsutsuji, Edo-kirishima, Satsuki and pot azalea have been developed. In this study, we focused on the genetic contribution of wild species to the development of evergreen cultivars and used microsatellite loci to examine the genetic involvement of wild species, particularly Rhododendron ripense. The utilization of seven microsatellite loci enabled cultivar identification and an estimation of bud mutation lines. The results of STRUCTURE analysis revealed that the R. ripense cluster was predominant in large-flowered cultivars such as Kishi-tsutsuji, Ryūkyū-tsutsuji, and Ōkirishima. The involvement of the R. ripense cluster was also observed in pot azalea developed in Western countries. Additionally, the genetic involvement of R. scabrum was confirmed in many cultivars of Ōkirishima and Hirado-tsutsuji. Regarding small-flowered cultivars, the Yama-tsutsuji and Kurume-tsutsuji cultivar groups were dominated by the R. kaempferi cluster, while the Satsuki cultivar group was dominated by the cluster containing R. indicum, R. eriocarpum, and others. These results enable us to reevaluate the classification of azalea cultivars by conducting a more detailed study of cultivar groups composed of the same clusters.
