Irrigation and rootstock effects on the phenolic composition of Vitis vinifera L

Phenolic compounds of the skin and seeds are the principal sources of wine color and structural properties. Under semi-arid conditions, irrigation management is the most determining factor of grape and wine quality while rootstocks affect numerous physiological and vegetative parameters of the scion. In the present study, compositional changes of skin and seed phenolic compounds were studied in a factorial experiment, in field-grown grapevines of cv. Cabernet-Sauvignon (Vitis vinifera L.) grafted onto 1103P and SO4 rootstocks and subjected to three irrigation levels (FI 100% of evapotranspiration, DI 50% of evapotranspiration and NI-not irrigated). The experiment was conducted in a ten-year-old commercial vineyard of central Greece over two years (2005-2006). Limited water supply decreased berry size but did not affect the skin-to-pulp weight ratio. Water limitation did not affect skin anthocyanin concentration at harvest. Irrigation regime (mainly post-veraison) and rootstock genotype affected total flavan-3-ol monomers in seed tissue, mainly as a result of variations in catechin amount. The lower seed phenolic concentration was found in non-irrigated and SO4-grafted vines and was probably related to the modification of cluster exposure due to restricted scion vigor.