Combined effects of early defoliation and deficit irrigation on yield components and chemical composition of grapevines 'Albariño′ grown in Galicia (NW Spain)

The combined effects of early defoliation and deficit irrigation on 'Albariño′ yield components and must chemical composition was assessed in a vineyard located in North-West of Spain during the 2016–2018 seasons. Early defoliation (ED), first six basal leaves pre-flowering, was applied to vines under three water regimes (T0—rainfed; T1—irrigated at 30% ETo from veraison to harvest; and T2—irrigated at 30% ETo from pea-size to harvest), and undefoliated controls (C) were established for each water regime. 'Albariño′ musts from each experimental treatment were analyzed to determine their chemical and volatile compositions. A reduction in bunch weight was detected in early defoliation treatments; however, higher yields were measured under T0 and T1 due to the weather conditions, with significant rainfall in spring. A seasonal effect greater than that of the treatment on the must chemical composition was observed. Early defoliation (ED) did not exhibit a significant effect on any must quality parameter. Total volatiles showed a higher concentration in the wettest season (2016) due to the highest concentrations of C13-norisoprenoids, esters, and acetates, with a general trend to an increase in their concentrations when ED was applied in T1 and T2. An adequate balance between grape yield and must quality was observed for T1-ED, which may represent a suitable management strategy for grape growers in this temperate climate region. Early defoliation reduces yield, mainly due to a lower bunch weight. Different irrigation strategies affect the quality parameters of the must, while early defoliation tends to increase volatile compounds.