CHARACTERISTICS OF INTERSPECIFIC HYBRIDS BETWEEN ACTINIDIA CHINENSIS KIWIFRUIT AND A. RUFA NATIVE TO JAPAN

Actinidia rufa, native to south western region of Japan, adapts well to warm climates, and has high cross compatibility with diploid A. chinensis kiwifruit. For the purpose of breeding new kiwi-berries adapted to warm conditions, the characteristics of the progenies from interspecific hybridization of A. rufa x A. chinensis (312 plants) and A. chinensis x A. rufa (334 plants) were evaluated. The leaf morphology of the interspecific hybrids was intermediate between the parental species. The flowers of the hybrids were generally larger than those of A. rufa. The fruit of the hybrids have hairless brown skin similar to that of A. rufa, but the green color of the flesh was lighter. The fruit weight ranged from 11.7 to 58.4 g. Phenologically, the interspecific hybrids flowered in early May halfway between A. chinensis in late April and A. rufa in late May. The fruit matured in late October, half a month later than those of A. chinensis and one month earlier than those of A. rufa. The fruit of interspecific hybrids contained total soluble solids (TSS) ranging from 13.5 to 22.0% and titratable acids (TA) from 1.0 to 2.6%. In the interspecific hybrids, total ascorbic acid in the juice ranged from 20 to 70 mg per 100 g FW, higher than in A. rufa fruit which contain about 15 mg. The content of chlorophyll in the fruit flesh was lower in the interspecific hybrids than in A. rufa. Protease activity was detected in the flesh but it was generally low. These results suggest the potential of the interspecific hybrids as the material from which superior clones can be selected.