Fertility assessment in Vitis vinifera L., cv. Alvarinho

La composition fine des raisins de Grenache noir est mal connue. Il est généralement admis une certaine variabilité de comportement de ce cépage qui se manifeste principalement sur la couleur des vins. De nombreux facteurs peuvent être à l’origine de cette variabilité : matériel végétal, pratiques culturales, types de vinification et terroir. Un travail de recherche concernant ce cépage a été engagé dans la Vallée du Rhône.

Wine aroma is a crucial quality criterion. A multitude of volatile compounds have been identified and correlated to the aroma attributes perceived in wine.

Varietal flavor is commonly known as the aromatic character of a wine in which the aroma of a particular grape variety predominates. However, not all varieties present particularly pronounced aromas. Therefore, different methods are constantly sought to enhance the aroma of wines with neutral aromatic characteristics, such as the use of glycosidases (1), certain yeast strains (2) or maceration with different agricultural products. In this work, aiming to improve the sensory profile together with the diversification of this product, white wines, derived from a neutral grape variety, were elaborated with the addition of mango peel by-products.

The advance in maturation of wine grapes is an important climate change risk related effect that could affect warm regions like Portuguese Douro Wine Region. Indeed, the climate analysis over the past years registered a decrease in the precipitation, significant higher average temperatures, and a more frequent occurrence of extreme weather events, including heat waves. In these conditions the length from anthesis until maturation is shortened and the uncoupling of technical and phenolic maturity results in berries with higher sugar concentration (and lower acidity), but lower anthocyanins, tannins, and total phenolic concentration, which produce unbalanced wines.
In this work, an innovative strategy of crop forcing, based on forcing vine regrowth after a second pruning of green shoots, was tested, aimed at delaying ripening until the temperature becomes lower and, therefore, preventing acidity loss and increasing anthocyanin-to-sugar ratio. The experiments were conducted in 2019 and 2020 in a commercial vineyard of ‘Touriga Nacional’ located in the Douro Region. Crop forcing was conducted 15 (CF1) to 30 (CF2) days after fruit set. Vines pruned with conventional methods were used as control (CF0). Results confirmed that fruit ripening was shifted from the hot season (August/September), until a cooler period (October through early-November). At harvest, grapevine berries from CF1 and CF2 presented lower pH and higher acidity, than control, with no significant differences in colour intensity and phenolic levels composition. Sugar content was lower in CF2-treated vines in both seasons. However, in CF-treated vines the number and size of clusters were significantly lower (up to 88% reduction) than in control plants. A metabolomics analysis of mature berries from CF-treated vines and control is underway. Crop forcing was indeed effective in producing a more balance berry composition but severely reduced grapevine yield,

Climate change poses significant challenges for viticulture, particularly in Mediterranean regions like Portugal, where extreme heat and drought conditions are becoming more frequent.