The white grape variety is cultivated in Japan; however, the origin and parentage (parentage) is unknown. Synonyms are Kochiou, Konshu, Koshiou, Koshiourebe and Koushuu. It is named after the former province of Kōshū, which roughly coincides with the present Yamanashi Prefecture. According to one hypothesis, it reached China from Europe via the Silk Road as early as the 8th century and was introduced to Japan by Buddhist monks. According to a second hypothesis, it was discovered by an Amemiyas Kageyu around 1186 in the south of the Kofu Valley at the foot of Mount Fujiyama. According to DNA analyses carried out in 2006, it is a species of Vitis vinifera, which makes the hypotheses unlikely. It is closely related to the Koshu Sanjaku variety. Koshu was a crossing partner of the new varieties Koshu Sémillon and Komahikari.
The late-maturing vine is susceptible to both powdery mildews, but resistant to botrytis. It is cultivated in the traditional Tanazukuri pergola system and is ideally suited to the climatic conditions in Japan. The rose-coloured, thick-skinned berries produce fresh, low-alcohol and rather low-extract, neutral-tasting white wines that serve as blends for red and white wines. Above all, however, it is used as table grape and also for the distillation of spirits. It is mainly grown in Yamanashi Prefecture on the main island of Honshu. In 2016, 690 hectares of vineyards were reported with a strong upward trend (Kym Anderson statistics).
Picture left: By Sophie Jacquin - Own work, CC BY-SA 3.0, Link
Image right: By genta_hgr - Grape, CC BY 2.0, Link
Source: Wine Grapes / J. Robinson, J. Harding, J. Vouillamoz / Penguin Books Ltd. 2012
