The use of elicitors in the vineyard to mitigate the effects of climate change on wine quality

Abstract

The wine sector is being directly affected by climate change. Temperatures above 30ºC can cause a lag between the ripening of the berry pulp (a rapid increase in sugar content) and the skin, due to the longer period required for the skin maturity (1,2). This leads to unbalanced wines, with high alcohol content and lacking in phenolic maturity (3). Many studies have been carried out searching for mechanisms to increase the content of polyphenols and to synchronize the two types of maturity. One option could be the use of elicitors, whose mechanism of action triggers biosynthetic pathways for defense compounds, including phenolic compounds (4). The objective of this study was to determine if the application of three different elicitors to Monastrell grapes during the maturation period could accelerate the synthesis of phenolic compounds and allow the obtention of wines with high phenolic concentration and moderate alcohol content. The elicitors used have been: LalVigneTM Mature, a compound made up of 100% specific fractions of Saccharomyces cerevisiae derivatives; Harpin αβ, a protein of bacterial origin; BION® 50 WG, a chemical inducer composed of the active material acibenzolar-S-methyl. This study has been carried out in 2019, in two different vineyards, one conducted with a trellis system and drip watered and the other one in a non-irrigated globet system. The treatment consisted in two applications at two different moments, at veraison and 14 days later. The grapes were harvested with 22ºBrix and also a control batch was harveted at 26ºBrix. Once the wines were bottled, the physicochemical and chromatic parameters by spectrophotometry were analyzed. The control wine from the trellised vineyard had an alcohol content of 13.81%, and the wines made with grapes treated with elicitors a presented 12.5%, 12.40% and 12.90% when Lavigne, Harpin and Bion were applied, respectly. The alcohol content of the wines made from the grapes from the non-irrigated vineyard was 14.37% for the control wine and 12.46, 13.18 and 12.85% for those made from grapes treated with Lavigne, Harpin and Bion, respectively. In both vineyards, the wines made from the grapes treated with the different elicitors have a lower pH and higher acidity than their respective control wine, mainly in the non-irrigated vineyard. Regarding the wine chromatic parameters and for the wines from elicitor-treated grapes from both vineyards, they presented higher tannin content and similar values of total phenols and color intensity than their control wines, not forgetting that the alcohol content of the former wines was one to two alcohol degrees lower than control wines. Therefore, the use of elicitors can be a promising treatment to speed up the accumulation of phenolics in the grapes so they can be harvested with a lower sugar content and obtain wines with less alcohol content and with an unaffected chromatic parameters.