Effects of Partial Defoliation on the Skin Polyphenolic Content of Syrah Grapes (Vitis Vinifera l.) Grown in Skopje Vineyard Area

Influence of partial defoliation on skin polyphenol content was studied for Syrah grapevine variety, grown in Skopje vineyard area. Partial defoliation (50%) only from east side of the row, from different developmental stages, beginning from 15 days after blooming (S1), than 30 days after blooming (S2), 15 days before veraison (S3) and 30 days after veraison (S4), was applied. Concentrations of total phenols, total anthocyanins and total flavan-3-ols in the skins, during berry ripening, were assessed by spectrophotometry. According to the results, defoliation applied 30 days after blooming (S2) allowed achieving highest content of total anthocyanins, total phenols and total flavan-3-ols in the berry skin, while defoliation made 15 days after blooming leaded to lower content of polyphenols compared to S2 and control vine. Variants S3 and S4 had the lowest content of total anthocyanins, total phenols and total flavan-3-ols, Thus, the best period for defoliation of the Syrah grapevine variety was 15 to 30 days after blooming, in order to increase polyphenolic skin content