Abstract
The intensity of bud dormancy, water content, and the endogenous levels of ABA-like substances in shoots of several wild grape species native to different regions of Japan were compared with those of Vitis labruscana Bailey, cultivar 'Muscat Bailey A', from September to December.
The onset of endodormancy (rest) in V. coignetiae Pulliat and V. amurensis Rupr., which are wild species of the more northern origin, was earlier than that in other wild species. Furthermore, the water content decreased during a period of bud dormancy, whereas, the levels of ABA-like substances increased sharply in October for these two wild species. In V. shiragai Makino and the cultivar 'Muscat Bailey A', the period of the deepest dormancy occurred in November. The water content of their shoots decreased gradually and the levels of ABA-like substances increased as the intensity of bud dor-mancy deepened. The period of the deepest dormancy of V. kiusiana Momiyama and V. sp. (tentative name Shiohitashibudo) was not well-defined, because these wild species ex-hibited low percentages of bud burst during the study period. Changes in shoot water content of these two species paralleled the changes in percentage of bud burst. However, the level of ABA-like substances in these wild species peaked in November. The period of the deepest dormancy in V. ficifolia Bunge var. ganebu Hatusima, which is of subtropical origin, occurred in November, but its intensity was lighter than that of other wild spe-cies. Its shoots also had higher water content and low ABA-like substances.
The results show that the onset and intensity of bud dormancy differed among the wild grape species and, generally, low shoot water content and high level of ABA-like subst-ances coincided with the time of deepest dormancy.
