Impact of Prebloom and Fruit-set Basal Leaf Removal on the Flavonol and Anthocyanin Composition of Tempranillo Grapes

The influence of timing and method of basal defoliation on the profile and content of anthocyanins and flavonols in Tempranillo grapes was investigated. Basal leaf removal was manually and mechanically performed at two phenological stages (pre-bloom and fruit-set). Phenolic composition was determined in grape extracts by HPLC-UV-Vis and 13 compounds, belonging to the groups of anthocyanins and flavonols, were identified and quantified. Regardless of the timing and method of defoliation, basal leaf removal led to more ripened fruit in terms of higher soluble solids and reduced acidity, and favored the accumulation of flavonols and anthocyanins, which was related to the increase in the total leaf area per yield observed in defoliated vines. For anthocyanins a significant relationship between the larger relative skin mass observed in berries of defoliated vines and their anthocyanin concentration was also found. In general, the enhancement in flavonols and anthocyanins observed in berries from basal defoliated vines tended to be larger when defoliation was conducted mechanically; yet overall no evident differences between pre-bloom and fruit-set treatments were found.