Anatomical Study of Primary Bud Necrosis in Vitis vinifera L. cv. Askari in Winter Dormant Bud

Primary bud necrosis in grapevine is a physiological disorder observed in the compound buds. This study was conducted to investigate the anatomical changes in cv. Askari grapevine in winter dormant buds. Bud samples were taken from Askari grapevine at Sisakht vineyards, south-western of Iran. Compound buds were dissected and assessed under a binocular microscope at 10-40x magnification and a digital microscope (Dinolite-AM413T) was used for taking photos. The results showed that the bud necrosis incidence was observed in primary buds more than in the secondary buds. Anatomical observations showed that PBN disorder occurred in central buds as brown small spot and gradually developed in the whole bud and bud necrotic remained on canes and did not abscission. On the results of present study, dissecting buds in autumn can raise awareness of PBN and fruitfulness of bud in the following spring, hence, growers should determine the level of bud necrosis prior to winter pruning so that pruning techniques might be adjusted to account for the bud damage.