effect of friutfulness and soluble suger and starch changes in stem, bud and leaf on primary bud necrosis in grapevine

primary bud necrosis (pbn) in grapevine is a physiological disorder that leads to death of fruitful buds and yield loss. the aim of this study was to determine the changes in soluble sugars and starch and their relationship to the incidence of the primary bud necrosis in askari grapevine. experiment was conducted in a vineyard that the vines were 15 years old, with a head system, vines spaced 2.5×3 m, as factorial in randomized completely block design with three replications during 2008. the first factor including to fruiting and de-fruited, the second factor 3 level of organ types (bud, leaf and stem) and the third factor with 10 level of sampling date (40 to 130 days after bud break (dab)).the results showed that the first symptom of pbn disorder began at the 60 dab and continued to end of growing season. also the concentration of soluble sugars increased in the early season and then it decreased, but the amount of starch in all organs, especially in bud increased. the concentration of soluble sugars and starch in fruited vine was more than the de-fruited vine. in both fruiting and de-fruited vines, when season ahead, the amount of storage starch was increased in all organs. a negative correlation of soluble sugar and starch with pbn percentage in the fruiting and de-fruited vines were observed. in other word, the role of soluble sugars and starch stored in the bud, on the incidence of pbn in askari grapevine was confirmed.