Impact of leaf removal after berry set on fruit composition and bunch rot in 'Sauvignon blanc'

Abstract

Leaf removal is a viticultural practice applied to improve cluster microclimate and grape composition. This practice can reduce the incidence of bunch rot but could also promote the degradation of berry methoxypyrazines, key components for the aromatic profile of 'Sauvignon blanc' wines. The influence of cluster-zone leaf removal, applied after berry set, was evaluated on 'Sauvignon blanc' grapevines grown in the Isonzo DOC region (Italy). In 2010 and 2011, yield components and fruit chemical composition were recorded from vines in which the five basal leaves of each single shoot were manually removed at the groat-sized phenological stage, and compared to untreated vines. Our results indicated that leaf removal did not influence yield or fruit composition at harvest, but significantly decreased the incidence and severity of Botrytis bunch rot, while reducing the severity of sunburn damage to the fruit. Increased sunlight cluster exposure decreased 2-methoxy-3-isobutylpyrazine (IBMP) and 3-isopropyl-2-methoxypyrazine (IPMP) concentrations in early stages of berry development, whereas at harvest no significant differences between treatments (defoliated and non-defoliated) were observed. We conclude that leaf removal performed after berry set is a pivotal viticultural management practice to cope with harvest bunch rot complex without negatively affecting fruit composition at harvest.