Hyun Hee Han

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

‘Sinano Sweet’ apple trees were defoliated at intervals of a month from May to October to simulate damage occured by hail and typhoon in Korea, accordingly fruit yield, reserve accumulations and return bloom were investigated. As the more severe defoliation degree was and earlier defoliation time was, fruit weight and fruit yields were more decreased. Fruit weight and yields of 30% defoliated trees, regardless of the defoliation time, showed no significant difference with those of control. Because carbohydrate contents of the 2-year old branches defoliated before August were even lower than those of branches defoliated after September, it was considered that defoliation time is more effective on the carbohydrate content than defoliation degree. Among the trees defoliated before August, 50% defoliated trees at August contained the lowest carbohydrate by 50% of control. Time and degree of defoliation had an effect on the number of flower buds following year. The number of return bloom in trees defoliated from May to July was decreased by delay of defoliation time and was the lowest in trees defoliated at July. On the other hand, it was not have a significant different between control and trees defoliated since August. Relationship between the number of return bloom and carbohydrate reserves showed positive correlation. As a result, it is considered that fruit thinning, when defoliation occurred in the growing season, needs for strengthening the sink function of remained individual fruit effect on fruit enlargement and for increaseing the carbohydrate reserve effect on return bloom. Additional key words : carbohydrate content, return bloom