Studies on the breeding of yellow-flowered evergreen azaleas through three way crossings.

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Until now, a lot of crossings between Rhododendron japonicum and several evergreen azaleas were done for the obtainment of yellow-flowered evergreen azaleas. But almost all seedlings were albino and have never grown at anthesis.In 1996, we tried single and three way crossings between R.japonicum and evergreen azaleas and investigated the rate of capsule set, number of ovules, leaf color and the hybridity of the seedlings. The green seedlings were obtained in the three way crossings whereas those were not in the single crossings.In 1997, we investigated the relationship between leaf color and ptDNA by PCR-RFLP and discussed about the factor of the appearance of albino seedlings.The ptDNA of albino seedlings obtained from the crossings between Fl of evergreen azaleas and R.japonicum were originated in seed parents (maternal inheritance) whereas the ptDNA of the green seedlings were originated from pollen parents (paternal inheritance). In general, ptDNA of azaleas were usually inherited from seed parents.From these results, it was suggested that the appearance of albino seedlings related with the inheritance of ptDNA in the interspecific crossings in azaleas. In addition. the appearance of albino seedlings seem to be originated in the incompatibility between ptDNA and nuclear DNA.