Irrigation pratices to improve varietal thiols concentration in white wines from cv. Colombard and Gros Manseng in Gascony, a vineyard under oceanic climate

Abstract

This work fits into adaptive technique for local viticulture in climate changing context. The purpose is to sustain the aromatic typicality of the wine, as aroma expression of white wines is here the main issue to market access. Gascony vineyard, in the south- western France, undergoes oceanic climate that occurs regular but heterogeneous rainfalls in summer. The aim of this experiment is to use irrigation practice as a tool to manage the vine water status for improving varietal thiols content in Colombard and Gros Manseng wines. Two plots have been studied between 2010 and 2014. Irrigation was led by drip system. Vine water status was rated by modelling soil water content, by measuring stem water potential and by analyzing carbon isotope in sugar at harvest. Two different strategies of deficit irrigation were tested each year during pre and post veraison periods. Grapes have been processed into wine at pilot scale on reductive condition to maximize their varietal thiols expression. The results showed, during the studied vintages, variability in rainfall conditions. Moreover, the two varieties had different behavior in relation with water availability. As expected, irrigated grapevines produced more sugar by hectare. Varietal thiols content in wines had not been systematically improved but had showed some interesting gain under specific conditions. Water status is one of the main co-factor in viticulture to contribute to varietal thiols in wines. This work allows to refine irrigation strategy for efficient use of the water resource.