response of askari grapes (vitis vinifera l.) bud to winter cold injury

due to physiological disorder, primary bud necrosis (pbn) in grapevine is a great problem in vineyards, resulting in reduced yield. primary bud necrosis (pbn) is physiological disorder resulting in the death of the primary bud. the present study conducted through a light on this critical problem in a vineyard of cisakht region. a factorial experiment with three levels of cold temperature (-10, -15, -20, -25 and 30 celsius degree) and cold duration with the three levels (12, 24, 48 h) in a completely randomized design in three replications in 2007 was performed. therefore, after preparing the cutting and transfer to lab, cold hardiness was tested by exposing single node cuttings in different cold temperature and duration treatments. indicators such as percent of primary bud necrosis, the percentage of secondary bud necrosis and electrolyte leakage were evaluated. the results indicated that up to -10 o c, buds were not affected. at -15 o c, primary bud necrosis (pbn) started to show necrotic symptom without affecting in secondary bud, but at -20 and -30 o c, the sever bud necrosis and higher ion leakage were seen in both primary and in secondary buds. also, the percentage of primary bud necrosis was higher than the secondary bud necrosis. there was a correlation between freezing temperature and incidence of primary bud necrosis and secondary bud necrosis in askari grapes.