Amphidiploid production of hybrid between black raspberry and Rubus parvifolius L., a wild Asian species, using colchicine treatment

The fruit of the black raspberry (Rubus occidentalis L.) contains numerous bioactive components such as poly-phenols, and the development of novel black raspberries with numerous functional components is eagerly desired. Rubus wild species in Asia, including Rubus parvifolius L., have been attracting a great deal of attention as sources of new traits in breeding raspberry and blackberry. In this study, we developed interspecific hybrids (BCP1 and BCP2) between black raspberry JP1 (Japanese accession 1) and the Asian Rubus parvifolius L. wild raspberry, and we confirmed interspecificity using simple-sequence repeat (SSR) markers. We then developed an amphidiploid using colchicine treatment and confirmed and evaluated it. Our results confirmed the interspecific hybridity of BCP1 and BCP2 using 4 SSR markers. In the colchicine treatment of BCP2, tetraploids were obtained after exposure to 0.1% colchicine for 2 days (7.7%) and 4 days (5.9%). The tetraploid of BCP2 showed vigorous growth, flowering, and fruiting in a warm region of Japan, and the flower diameters of BCP2 (4x) were significantly larger than those of BCP2 (2x). Also, the fruit color was confirmed to be black, the same as the fruit of JP1. We believe our research will support the development of black raspberry breeding and may contribute to ploidy breeding between black raspberries and wild Asian species as a new genetic resource for environmental adaptability.