Japanese azalea germplasm; the living horticulture properties
Evergreen azalea is one of the major ornamental shrubs and pot plants of Japanese origin. The Japanese endemic species classified in the genus Rhododendron (Ericaceae), the subgenus Tsutsusi, section Tsutsusi such as R. kaempferi, R. indicum, R. macrosepalum, R. ripense and R. scabrum, have a high ornamental value in nature. Based on the genetic diversity of these wild azaleas, hundreds of cultivars have been selected from natural populations and bred in gardens intensively since the Edo era (1603-1867). In the first monograph of azalea titled Kinshū-makura (Brocade pillow) published in 1692, 335 azalea cultivars including the mutations of flower shapes or colors were already presented at that time. Since then, varietal Japanese cultivar groups have been developed and several cultivars have been introduced to Western countries as new Oriental ornamentals and used as breeding materials of potted and garden azalea. We have been conducting a wide range of azalea research from the evaluation of genetic resources to practical and molecular breeding. The research project has obtained several outcomes about the flower shape mutations with the related MADS-box genes, the flower color pigments with the related biosynthetic genes, the genetic contribution of wild species to cultivar development and the breeding programs combined with the traditional cultivars and molecular markers. The endemic species and the traditional cultivars developed from them are valuable as genetic resources of the accumulated mutational genes and also as living horticultural properties. I am hoping that our research project will bring light to azalea germplasm and Japanese traditional horticulture.
Kobayashi, N. (2020). Japanese azalea germplasm; the living horticulture properties. Acta Hortic. 1291, 163-168
cultivar development, endemic species, genetic diversity, Rhododendron, traditional horticulture