Interspecific Hybridization Using Miyama Matatabi (Actinidia kolomikta), a Japanese Indigenous Wild Kiwifruit Relative

抄録

Actinidia kolomikta (Maxim. & Rupr.) Maxim., a wild kiwifruit relative native to East Asia, has several desirable characteristics, such as strong cold tolerance, precocity, and high levels of vitamin C, and has therefore attracted horticultural interest. In this study, the interspecific cross compatibility of the diploid Actinidia kolomikta with one cultivated species [A. deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson], three native Actinidia species [A. arguta (Siebold & Zucc.) Planch. ex Miq., A. polygama (Siebold & Zucc.) Maxim., and A. rufa (Siebold & Zucc.) Planch. ex Miq.], and one endemic variety [A. arguta (Siebold & Zucc.) Planch. ex Miq. var. hypoleuca (Nakai) Kitam.], was evaluated to see if interspecific hybridization using A. kolomikta could improve edible Actinidia crop breeding programs. There was no fruit setting two weeks after anthesis in the tested cross combinations when A. kolomikta was the male parent. In contrast, all five crosses using A. kolomikta as the female parent produced 100% fruit setting two months after pollination. The crosses with different ploidy levels such as combinations between diploid A. kolomikta and hexaploid A. deliciosa, or diploid A. kolomikta and tetraploid A. arguta, produced a few viable seeds. In contrast, the crosses with diploid species such as A. arguta var. hypoleuca, A. polygama, and A. rufa, produced many viable seeds and seedlings. From these results, the cross compatibilities of A. kolomikta with the other tested species were categorized as follows: no fruit setting (A. arguta × A. kolomikta and A. polygama × A. kolomikta); fruit setting with few viable seeds (A. kolomikta × A. arguta and A. kolomikta × A. deliciosa); and normal fruit setting with viable seeds (A. kolomikta × A. arguta var. hypoleuca, A. kolomikta × A. polygama, and A. kolomikta × A. rufa). These results could be a basis for future edible Actinidia crop breeding programs using A. kolomikta and interspecific hybridization.