Studies on the seasonal depth of rest, chilling requirement, and the effective methods for rest breaking of several grape cultivars have been carried out from 1983 to 1985. A summary of these studies is as follows.
Under natural environments, `Schuyler´, `Delaware´ and `Muscat Bailey A´ grapes developed a rapid progress of rest from early September and went into deep rest during the period between early October and early November, followed by a gradual recovery from the rest. `Golden Muscat´ and `Golden Queen´ gripes developed a gradual progress of rest from early September and went into deep rest during the period between early Novembar and early December for `Golden Muscat´ cultivar, and the deep rest was during the period between late December and late January for Golden Queen cultivar, followed by relatively rapid recovery from the rest by February of the following year for both cultivars. Relationship between ripening seasons of cultivars and length of chilling requirement was not consistent.
The best method for the rest breaking was hot air treatment with 45℃ for 6 hours. Low temperature (0℃) treatment for 2 to 3 months showed effective rest breaking. The chemical treatments of 2% thiourea, supernatant of 20% calcium cyanamide and 10ppm ethephon gave fairly good results for rest breaking, whereas gibbrellic acid(GA₃) prolonged the rest period.
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