Phenological stage dependency of Cabernet Sauvignon and Grenache response to water and nutrient limitation 

Cette recherche a eu pour but l’étude des effets d’un renforcement radiatif et thermique sur les zones inférieures de la canopée de la vigne (solarisation par des films ou des paillages réfléchissants installés sur le sol, sous les ceps), notamment l’étude de leurs conséquences sur la composition biochimique des moûts à la vendange et sur la qualité des vins.

In 2008 the anthocyanin, flavonol and hydroxycinnamate (HCT) contents of the skins of five coloured berry cultivars (‘Escursac’, ‘Esperó de Gall’, ‘Galmeter’, ‘Valent negre’ and ‘Vinater negre’), of two white cultivars (‘Argamussa’ and ‘Prensal blanc’) and of one weakly rose cultivar (‘Giró ros’), native from Balearic Islands, were characterized.

Rotundone is the main aroma compound responsible for peppery notes in wines whose biosynthesis is negatively affected by heat and drought. Through the alteration of precipitation regime and the increase in temperature during maturation, climate change is expected to affect wine peppery typicality. In this context there is a demand for developing sustainable viticultural strategies to enhance rotundone accumulation or limit its degradation. It was recently proposed that ultraviolet (UV) radiations could stimulate rotundone production. The aim of this study was to investigate under field trial conditions the impact of grape exposure and UV treatments on rotundone in Vitis vinifera L. Tardif, an almost extinct grape variety from south-west France that can express particularly high rotundone levels. Four different treatments were compared in 2021 to a control treatment using a randomised complete block design with three replications per treatment. Grape exposure was manipulated through early or late defoliation. Leaf and laterals shoots were removed at Eichorn Lorenz growth stages 32 or 34 on the morning-sun side of the canopy. During grape maturation, UV radiations were either reduced by 99% by installing UV radiation-shielding sheets, or applied four times using the Boxilumix™ non thermal device (Asclepios Tech, Tournefeuille) with the aim of activating plant signalling pathway. Loggers displayed in solar radiation shields were used to assess the effect of such shielding sheets on air temperature within the bunch zone. The composition of grapes subjected to these treatments will be soon analysed for their rotundone content and basic classical laboratory analyses. Grapes will be harvested to elaborate wines under standardized small-scale vinification conditions (60kg) that will be assessed by a trained sensory panel.

La caractérisation des terroirs viticoles est traditionnellement basée sur des descripteurs de la géologie et de la pédologie des différents milieux rencontrés, couplées à des données climatiques

The wine industry widely recognizes that early-harvested grapes or those with uneven ripeness at harvest can produce wines with an “unripe fruit” mouthfeel [1,2]. Despite this, it is still unknown which compounds cause these sensory flaws or the most effective winemaking techniques to address them.