Early defoliation is a novel cultural practice for crop management in grapevines. The effects of timing (prebloom or fruit set) and method (manual or mechanical) of early defoliation on yield and grape and wine composition of Vitis vinifera L. cv. Graciano and Carignan grapevines were investigated. Leaf removal induced a substantial increase in both cluster exposure and canopy porosity. Yield was significantly reduced by defoliation in both varieties. Yield per shoot was reduced between 30 and 70% by manual and mechanical leaf removal prebloom. In both varieties, postflowering leaf removal was ineffective at modifying fruit set, number of berries per cluster, or yield per shoot. Botrytis incidence was also reduced by leaf removal. Prebloom defoliation allowed full recovery of the leaf:fruit ratios to that seen in nondefoliated vines. Grape soluble solids and wine alcohol concentration were not affected by defoliation. Malic acid decreased with leaf removal at fruit set. Genotype-environment interactions on berry acidity variables such as titratable acidity and tartaric acid concentrations were found. Early leaf removal substantially increased anthocyanin and phenol concentration in grapes and wine of both varieties. In Carignan, early leaf removal resulted in heavier berries, which nevertheless had enhanced grape and wine color. These results support the hypothesis that in early-defoliated vines, the relative growth of various berry organs is affected independently from absolute berry mass. Mechanical early defoliation has the potential to be a cost-effective technique to control yield and to improve grape and wine composition.
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