Breeding for Heat Resistant and Perpetual Flowering Azaleas

(1) Introduction of heat resistance into deciduous azaleas and Kurume azaleas : Survived seedlings of F_1 hybrid from the crosses among deciduous azaleas and those from the cross of Rhododendron eriocarpum×Kurume azaleas grown under high temperature and high humid condition in Kagoshima region showed a heat and humid tolerant characteristics. (2) Introduction of perpetual flowering into Hirado azaleas : Most of the F_1 hybrids from the cross of R. oldhamii×Hirado azaleas flowered in early autumn to late winter season. Perpetual flowering property found in R. oldhamii was introduced into Hirado azaleas. (3) Introduction of evergreen leaves into deciduous azaleas : All F_1 hybrids from the crosses using R. tashiroi as a seed/pollen parent had evergreen leaves. Evergreen-property found in R. tashiroi was introduced into the seedlings of F_1 hybrid. (4) Introduction of flowers with double (hose-in-hose) petals into R. eriocarpum×Kurume azalea hybrids : Nearly 50% of F_1 hybrids from the crosses using Kurume azaleas as a pollen parent had flowers with hose-in-hose petals. It suggests that genes controlling hose-in-hose trait in Kurume azaleas are genetically dominant and genotypes of Kurume azalea are heterozygous. (5) Improvement of flower colors in deciduous azaleas, Kurume azaleas and Hirado azaleas : F_1 hybrids from the crosses among deciduous azaleas and those from the cross of Rhododendron eriocarpum×Kurume azaleas had a dominant light purplish-red flower color. F_1 hybrids from the cross of R. oldhamii×Hirado azaleas had a dominant light purplish-red flower color, recessive salmon flower color and intermediate color between parent plants. It suggests that the gene controlling delphinidin production is not genetically dominant and Hirado azalea has heterozygous genotype on the pigmentation of delphinidin.