Effects of Timing of Manual and Mechanical Early Defoliation on the Aroma of Vitis vinifera L. Tempranillo Wine

Abstract

Early leaf removal is an innovative cultural practice for yield management in grapevines. The effects of timing (prebloom and fruit set) and method (manual or mechanical) of defoliation on yield components, Botrytis incidence, and wine sensory attributes of Vitis vinifera L. cv. Tempranillo VSP-trained grapevines were examined over two consecutive seasons, 2007 and 2008. Yield per vine was severely reduced (15 to 50%) by manual and mechanical leaf removal at prebloom in the two years and smaller clusters with fewer berries were obtained. At fruit set, only mechanical defoliation was effective at modifying cluster weight, berry number, and yield per vine. Botrytis rot incidence was significantly reduced by early leaf removal in 2008, when an overall higher infection rate was linked to unusually high rainfall. Total leaf area was generally unaffected by early leaf removal. Prebloom defoliation exhibited full recovery of leaf:fruit ratios compared with nondefoliated vines, regardless of defoliation method. Descriptive analysis of the aroma attributes of the wines revealed lowered intensity of fruity, floral, and licorice in the defoliated samples in 2007. Intensity scores for these descriptors were positively correlated to yield and negatively correlated to total leaf area:yield ratio. When Botrytis rot was widespread, the extent of infection was negatively correlated to certain fruity and floral aromas and positively correlated to dried fruit character. Several factors linked to early defoliation, such as yield, Botrytis, and cluster exposure significantly contributed to final wine aroma properties. Principal component analysis illustrated the separation of wines from defoliated and nondefoliated treatments by aroma profile.