Characteristics of Dorsal Leaf Surface, Implicating the Relationship between Ryukyu Azalea[Rhododendron mucronatum (Blume) G. Don]and Kurume Azalea[R. obtusum (Lindley) Planch.]

Abstract

To verify the presence of Ryukyu azalea (Rhododendron mucronatum) genes in Kurume azalea (R. obtusum), dorsal leaf surfaces were examined on 58 progenies of Kurume azalea 'Susogonoito'× R. macrosepalum, 58 cultivars of Kurume azalea, 8 cultivars of Ryukyu azalea, 5 cultivars of Mochi azalea, and 4 cultivars of Ookirishima azalea. The epidermal cells, cuticular topography and stomata, and the existence of vein trichomes were examined and described. In progenies between Kurume azalea 'Susogonoito'× R. macrosepalum, 87.9% exhibited more than one, among 3 epidermal characters, which were similar to R. macrosepalum. Vein trichomes, which occur on R. macrosepalum, appeared on all progenies. Twenty-three of 58 cultivars of Kurume azalea had more than one, among 4 dorsal leaf surface characters, which were similar to R. macrosepalum and R. mucronatum var. ripense. Seventeen cultivars of Ryukyu azalea, Mochi azalea and Ookirishima azalea possessed dorsal surface characters which were similar to those members of R. macrosepalum and R. mucronatum var. ripense. These results suggest that R. macrosepalum and/or R. mucronatum var. ripense which are species of Ryukyu azalea, may be related to the Kurume azalea.