Influence of harvest date and water deficit on grape aroma potential and wine quality of Vitis vinifera L. cv. White Grenache

Abstract

Vitis vinifera L. cv. Garnacha blanca (White Grenache) is the dominant grape variety in the D.O. Terra Alta (Tarragona, Spain), where it has been irrigated during recent years. However, there are no studies about the most suitable irrigation schedule and the consequences of advancing or delaying the vintage on White Grenache grape and its wine aromatic profile. The aim of this work, presenting 2014 season results of research initiated in 2012, was to evaluate effects of these two variables on grape quality, focusing on grape bound aromatic precursors (mainly terpenes, norisoprenoids, C₆ compounds, higher alcohols and esters), analyzed by GC-MS. Three levels of water deficit were induced using different irrigation rates, from a no deficit treatment (ND) to rainfed (R), plus an intermediate treatment (MD), all of them replicated four times in the vineyard; deficit thresholds for each treatment were set weekly based on pre-dawn water potential measurements (Ψpd). Secondly, grapes from each irrigation treatment were harvested and analyzed at three different times: normal “typical” harvest time (TH), advanced harvest (AH, 10 days before) and delayed harvest (DH, 10 days after) There were differences between irrigation treatments in all the vine physiology variables. There were also important differences in yield, due to berry weight. In general, aromatic precursor concentrations were higher at the delayed harvest, and aromatic potential increased with time. Although water deficit treatments had no influence on aromatic precursors (except benzeneacetaldehyde), there was a tendency of higher aromatic concentration per berry in the less stressed vines, and wines from ND treatment were rated as the most aromatic (but vegetal) ones by panelists.