A new approach in the adaptation of varieties to global warming: varietal differences in sugar content at veraison

Abstract

In warm climatic conditions, the red sugar concentrations of red varieties reach more than sufficient levels for obtaining high quality wines, but this is often not the case with colour. This relative stability of sugars compared to the sensitivity of anthocyanins to temperature is due to the different temperature ranges for optimal activity of the enzymes producing sugars (18 to 33º C) and pigments (17 to 26º C). Temperatures above 30º C can inhibit the formation of anthocyanins. This trend toward increasing temperature due to climate warming, emphasizes the decoupling between anthocyanins and sugars and produce very alcoholic wines.

With the aim to search genotypes existing and more apt to produce low-alcohol wines, we studied some minor varieties of the DOCa Rioja. We investigated the possible decoupling between anthocyanins and sugars in different minor grape varieties. We analysed the sugar content at the onset of ripening under the same cultivation conditions.

There were significant differences between minor varieties of DOCa Rioja with respect to the concentration of sugar at the beginning of veraison. Varieties with lower sugar concentration are Alicante Bouschet (Garnacha Tintorera), Moristel and Trepat. Such varieties would be best adapted to the climate warming trend. It should also be noted that there was no relationship between the concentration of sugar at the beginning of veraison and the date at which veraison occured.