Abstract
The usefulness of scaly rhododendrons in hybridizing with Kurume azalea (cultivar group of Rhododendron × obtusum) cultivars was examined in order to expand the variations of the Kurume azalea group. One R. keiskei and one R. mucronalutum var. ciliatum were used as pollen parents for pollination of eight Kurume azalea cultivars. The degree of post-mating barriers and the characteristics of hybrid seedlings were compared with those of previous crossings using R. japonicum f. flavum as a pollen parent. Hybrid albinism was remarkable for pollination with pollen of R. keiskei. Both the lack of seed germination and hybrid albinism were remarkable following pollination with pollen of R. mucronalutum var. ciliatum. We considered that these crossings had stronger post-mating barriers than crossings using R. japonicum f. flavum as a pollen parent. Of the 16 cross combinations we examined, only Kurume azalea ‘Gofuku’ × R. keiskei produced 12 healthy hybrid seedlings, and five of these flowered five years after pollination. The flower size of seedlings was equivalent to that of Kurume azalea cultivars. The leaves of the seedlings were coriaceous with better gloss that shown by either of parents. These useful traits did not appear in the hybrid seedlings obtained from crossings using R. japonicum f. flavum as a pollen parent. PCR-SSCP analysis demonstrated that ptDNA of the four hybrid seedlings examined was inherited paternally.
