Apricot flower bud development and abscission related to chilling, irrigation and type of shoots

12 pages, 2 tables, 3 figures.Flower bud drop dramatically affects productivity in some apricot cultivars. The influence of different chilling and irrigation conditions on flower bud development and drop of the apricot cv. ‘Guillermo’ was studied. Flower buds from trees grown in three places, with different winter conditions, were collected periodically to compare their developmental stage. Slight differences in the developmental pattern were observed between the two coldest places. Just before bloom, flower buds from the warmest place were found to be more delayed. Also, flower bud development was compared in three irrigation treatments. The lack of autumn irrigation induced a slow development, but when irrigation was reinstated, the flower bud development was hastened. The suppression of irrigation in winter did not have an apparent effect on flower bud development compared with the more irrigated treatment. In flower buds of short shoots no important abnormalities were found, but they were in the analysed flower buds of long shoots. In ‘Guillermo’ cultivar a serious drop was recorded in every location or treatment. However, no correlation was found between accumulation of chill unit or irrigation treatments and flower bud drop or fructification. In long shoots, the heavy flower bud drops (more than 90%), together with the high number of malformed flower buds, indicate that they do not produce an acceptable fruit set in this apricot cultivar.This work has been supported partially by a grant from the ‘‘Fundación Séneca’’ (Murcia, Spain).Peer reviewe