ヤマブドウ研究― 樹及び果実の特性 ―

Vitis coignetiae Pulliat is one of the naturally growing grape vines in the Japanese Islands, of which the fruit has been utilized as a healthy juice and wine. In Hiruzen Highlands, the vines have been cultivated for wine making since the 1980's. We have studied the physiology of berry set and berry maturation of the vines to improve the fruit production and fruit quality for last 14 seasons. V. coignetiae vines are dioecious and need insect pollination, mainly by two species of Diptera, Eristalis tenax and Eristalis cerealis, and one species of Hymenoptera, Ceratina japonica, indicating that mix planting with male vines and reservation of such insects are recommended. Once pollen grains have pollinated onto the stigma, most of them grow a pollen tube to penetrate into ovule tissue and finally reach the embryo sac to complete ovule fertilization. There are several types of coignetiae vines in Hiruzen vineyards that have different genetic backgrounds. RAPD analysis of 15 vines revealed that they can be divided into three groups and two individuals. Coignetiae vines have been found to have a lower tolerance for water logging than other cultivars, whereas they have moderate drought tolerance. Furthermore, coignetiae vines are not very disease tolerant, especially toward downy mildew, indicating that growers must take sufficient care over drainage and fungus control. V. coignetiae vines accumulate high levels of sugar and acid into the flesh and anthocyanins in the berry skin when they reach the full ripe stage, which is mid and late October in Hiruzen. Tartaric acid, the main acid constituent in coignetiae berries, is contained at levels as high as 1.0%. Amino acid concentration in the juice is much lower in most coignetiae vines than other wine grapes, although a special coignetiae vine with berries with high amino acid content has been found. V. coignetiae berries have been proved to have several functional properties such as high free radical scavenging activity and anti-photodecomposition of anthocyanin pigments. As commercial products of coignetiae berries, beautiful wines, pure juice, and wine vinegar with a rich and fruity taste are produced.