This study was conducted to determine the correlation between the natural incidence of primary bud necrosis (PBN) with cane diameter, node position and sampling date. Compound buds at nodes 1 to 20 from mature canes with diameters of >10 mm and < 10 mm were dissected and assessed for the presence of PBN. Results indicated that the effect of cane diameter, node position and date of sampling as well as interaction of diameter×node, diameter × date and node×date on the incidence of PBN were significant. However, the highest percentage of PBN (19.3%) was observed on thicker canes and the lowest (7.74%) was observed on thinner canes. From the viewpoint of bud position, nodes from 1 to 5 and from 16 to 20 on canes had the highest (39.57%) and lowest (0.2%) PBN, respectively. Also, the highest of PBN% was observed in February (18.09%) and March (18.78%). The interaction showed that there was a positive correlation between thickness of cane and nodes proximal position on percent of PBN. When sampling date was delayed, the incidence of PBN was greater in proximal nodes than distal ones. Results of the present study showed that PBN is an important factor responsible for low fruitfulness in vineyards under consideration.
