TETRAPLOID TABLE GRAPE BREEDING IN JAPAN
A table grape breeding program has been ongoing at the National Institute of Fruit Tree Science (NIFTS) since 1968. Its main objective is to release new excellent cultivars that well adapted to Japanese climatic conditions. In addition, large berry size, high eating quality (particularly firm and crisp flesh), and no berry cracking are the principal considerations. Furthermore, new cultivars should be converted to be seedless easily with gibberellic acid (GA) treatment because seedless berries are a desirable commodity for consumers. For the improvement of berry size, tetraploid cultivars/selections are used as cross parents and five tetraploid cultivars for table use have been released by NIFTS as of 2009. Aki Queen is a result of the selfing of Kyoho and its fruit ripens slightly earlier than that of Kyoho. Its berries are rendered seedless and weigh 13 g on treatment with GA twice, and are bright red in color. Sunny Rouge is a result of a cross between Pione and Red Pearl and its fruit ripens earlier than that of Kyoho and later than that of Delaware. Its berries are rendered seedless and weigh 6 g on treatment with GA twice, and are red-brown to violet red in color. In the GA non-treated condition, the bunch is not well filled due to berry shattering. Dark Ridge is a result of a cross between Kyoho and 301-1 (Kyoho × Niabell) and its ripening time is the same as that of Kyoho. Its berries are more evenly-black colored than those of Kyoho even in warm regions in Japan, and weigh 12 g in the GA non-treated condition. Honey Venus is a result of a cross between Benizuiho and Olympia and its ripening time is the same as that of Kyoho. Its flavor seems to be a mixed one of muscat and foxy. Its berries weigh 10 g in the GA non-treated condition. Recently, seedless berries of Honey Venus have begun to be produced in several regions in Japan. The flesh of these cultivars is firmer and crispier than that of Kyoho and the berries of these cultivars except Sunny Rouge are larger than 10 g. At present, ways to enhance resistance to fungal pathogens are under investigation.
Mitani, N., Ban, Y., Sato, A. and Kono, A. (2014). TETRAPLOID TABLE GRAPE BREEDING IN JAPAN. Acta Hortic. 1046, 225-230
Vitis, berry weight, eating quality, berry texture, ploidy level