Viticultural zoning applications at the detailed scale of a cooperative winery: terroirs in St­hilaire-d’Ozilhan (AOC Côtes-du-Rhône)

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Global warming is accelerating grape ripening, leading to unbalanced wines from fruit with high sugar content but poor aroma and colour development. Reducing the size of the photosynthetic apparatus after veraison has been shown to delay technological ripeness in cool climates, but methods have not been tested in areas with high irradiance and temperature where fruit exposure could have disastrous effects on berry composition. In this Cabernet-Sauvignon trial, we compared the application of an antitranspirant (pinolene), to severe canopy topping and above bunch zone leaf removal, all performed at mid-ripening, with an untouched control. We monitored the vines weekly by measuring stem water potential, gas exchange, fruit zone light exposure. We sampled berries to measure berry weight, total soluble solids, pH, titratable acidity, and the anthocyanin profile. At harvest, we assessed yield components, measured carbon isotope discrimination, rated sunburn on clusters, and produced experimental wines. We submitted harvest samples to metabolomic profiling through PFP-Q Exactive MS/MS and wines to sensory analysis. Application of the antitranspirant significantly reduced stomatal conductance and assimilation rate but did not affect the stem water potential. Inversely, leaf removal and topping increased water potential but did not affect leaf gas exchange. The late topping was the only treatment able to decrease sugar content (up to 2Bx), increase titratable acidity and pH, and improve anthocyanin content because of lower degradation of di-hydroxylated forms. Late leaf removal above the bunch zone increased lightning conditions in the canopy and produced the most significant damage on fruits. Yield components were not affected. This work suggests that late-season canopy management can effectively control ripening speeds and improve grapes and wines. Still, the effect on grape exposure in a critical time must be well balanced to avoid problems with the appropriate technique.

Controlling the development of the bacterial population during the winemaking process is essential for obtaining correct wines[1]. Carbonic Maceration (CM) wines are recognised as high-quality young wines. However, due to its particularities, CM winemaking implies a higher risk of bacterial growth: lower SO2 levels, enrichment of the must in nutrients, oxygen trapped between the clusters… Therefore, wines produced by CM have slightly higher volatile acidity values than those produced by the destemming/crushing method[2].

According to the World Economic Forum and the European Union’s Biodiversity Strategy for 2030, the loss of biodiversity and the collapse of ecosystems are major threats facing humanity in the future.

The prospective study of the French wine sector (Sebillotte et al., 2004) has identified “groups of micro-scenarios” at the end of the analysis of the characteristics of this wine sector.