A Study of the Disease Occurrence Date, Severity and Anatomical Changes due to Bud Necrosis in Different Stages of Growth and Development of Grapevines (Vitis vinifera L. cv. Askari)

Primary bud necrosis is a physiological disorder that adversely affects the performance and yield in the vineyards. The present study was conducted to determine the time and intensity of bud necrosis incidence as well as the related anatomical changes in the developing buds of grapevine cv. Askari. A factorial experiment in a randomized complete block design of 4 replications was carried out for the purpose. A first factor taken into account was comprised of two levels of fruit removal treatments (with and whithout fruit), while the second factor being comprised of 10 levels of sampling dates, starting from 40 to 130 Days After Bud break (DAB), with 10 days intervals. A digital microscope was used to determine the percentage of necrotic buds as well as the healthy ones. The results revealed that the effects of fruit removal and sampling date as well as their interactions were significant on percent bud death at a 1% level. Both fruiting and de-fruited vines, bore the lowest bud necrosis at 40 and 50 DAB while the highest percentage of bud necrosis occurred at 130 DAB. The outward appearances of a healthy and a necrotic bud seemed the same and the first symptom of the necrosis disorder commenced at the 60 DAB. Anatomical observations of bud tissue revealed the incidence of bud necrosis within the central bud as a brown spot appearing and gradually expanding. Compound bud, carrying the initial necrotic bud remains on the vine and does not fall off the shoots.