High quality wine grapes are mostly produced in dry and cool regions of the world. In Western Japan, a long rainy season from early summer until berry ripening causes excessive shoot growth. This high vigor leads to severe competition for photosynthates between shoots and clus- ters with negative affects on berry ripening. Thus, wines tend to have a flat taste.
Planting grapevines in isolated soil beds under a plas- tic-film cover can control vigor by root-zone restriction; this improved berry quality significantly (IMAI et al. 1991). Under such conditions, the level of soil moisture can be easily manipulated. A number of reports indicate that water deficit stress during the late stage of berry development improves berry and/or wine quality mainly by decreasing berry size
(MATTHEWS and ANDERSON 1988, PONI et al. 1993). On the other hand, early water deficit stress may cause severe inhi- bition of berry growth and maturation as a result of the de- cline of photosynthesis (DÜRING 1998).
In this study, we compared the effects of early and late water deficit stress on ripening of Chardonnay berries in relation to changes in the levels of leaf and berry ABA, which is reported to control berry ripening (COOMBE and HALE 1973; DÜRING and ALLEWELDT 1980).