Elucidation of the mechanism of occurrence of chilling requirement induction stage of dormancy

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Artificial regulation of breaking dormancy and genetic control of chilling requirement were investigated at induction stage of chilling requirement in Peach. 1)Lateral buds of basal position in shoot in high-chill cultivars entered into dormancy early July, and get into deep dormancy in September. Ca-cyanamide treatment enhanced bud break even at induction stage of dormancy. Temperature nor supplemental lighting affected the timing of induction of dormancy. 2)Low-chill cultivars could burst at high percentage and flowered normally even after only 350 chilling hour. In these cultivars, the immediate increase of sensitivity to temperature for bud burst is a possible reason of early bud burst and flowering. 3)Bud break and flowering largely depended on the chilling requirement of scion cultivar. The chilling requirement of rootstock affected the time and rate of bursting of leaf buds, but not flower buds. 4)High temperature adversely affected the development of embryo sac. 5)Cyanamide and Ca-cyanamide were more effective than Aryl-disulfate in breaking dormancy. However, the efficacy reduced at deep dormant stage. 6)The mRNA extracted from the leaf and flower buds at dormant and post dormant stages, was analyzed subtraction method. Several genes having different amount of transcription between dormant and post dormant stages were observed, and the gene related to the regulation of the cell cycle was included. 7)Crossed seedlings between high-chill 'Hakuho' and low-chill cultivars showed less chilling than 'Hakuho'.