Irrigation and Leaf Removal Effects on Polyphenolic Content of Grapes and Wines Produced from cv. 'Agiorgitiko' (Vitis vinifera L.)

Vitis vinifera L. cv. 'Agiorgitiko' is one of the most important red grape varieties of Greece, cultivated almost exclusively in the region of Nemea in north-eastern Peloponnese. This work aimed to study the influence of some commonly applied viticultural practices on the polyphenolic composition of 'Agiorgitiko'. Leaf removal at veraison, irrigation, and a combination of both, were applied and the phenolic content of the grapes and of the produced wines was compared. The results showed that leaf removal decreased berry size, enhanced total anthocyanin, total phenol and malvidin 3-O-monoglucoside accumulation in skins and increased the amount of extractable anthocyanins in the juice. The combination of irrigation and leaf removal caused a significant increase in total phenols in the skin and in the amount of extractable anthocyanins in juice. As far as the produced wines were concerned, color intensity, tannin content and total polyphenols were increased due to leaf removal. Both irrigation and leaf removal resulted in wines with the highest concentration of malvidin 3-O-monoglucoside, although neither practice resulted in any significant difference in anthocyanin concentration of the wines. Vines where only irrigation was applied produced berries with reduced extractable anthocyanins, increased seed total phenols and lower wine total tannins. The study showed that increasing cluster sun exposure of 'Agiorgitiko' vines may be, overall, beneficial to the quality of the produced wine.