Abstract
In order to develop new cultivars adaptable to Japan with high quality and functionality, we attempted to produce interspecific hybrids between Vaccinium uliginosum L. (2n = 6x = 72) of the genus Vaccinium, a wild species native to Japan, and some highbush blueberry cultivars (2n = 4x = 48) of the genus Cyanococcus, using reciprocal crossing. Fertile seeds were obtained from 8 of 9 cross combinations, and 13 seedlings were obtained from 5 cross combinations when V. uliginosum were used as a seed parent, but only 7 seedlings from 2 of 9 cross combinations as pollen parent. It was revealed that seeds were easier to obtain when V. uliginosum was used as a seed parent compared with pollen parent, and unilateral cross incompatibility occurred in the reciprocal cross. These seeds germinated in vitro after pretreatment with gibberellin or in a seed bed after stratification. Four resultant seedlings (KB4: KB-2, 7, 9, 10) from the cross of V. uliginosum and ‘Bluecrop’ were grafted on rootstock and evaluated regarding their hybridity, ploidy level, morphological characteristics of the flower and fruit, and fruit quality. RAPD analysis showed that KB4 was a hybrid between Vaccinium and Cyanococcus. The hybrids were also confirmed to be pentaploid by flow cytometry and observation of the chromosome number in shoot tip cells; however, they produced fertile pollen and set fruits in an open field without artificial pollination. Fruit of all hybrids also had a peduncle with a pair of leaflets differing from one of their parents. Although the contents of anthocyanin and polyphenol and antioxidant capacity of fruit were different among their hybrids, those values of KB-2 were significantly higher than in ‘Bluecrop’. In the future, these hybrids may be useful as breeding material to establish new cultivars with high quality and functionality.
