Mining microbiome data to identify antagonists of grapevine downy mildew (Plasmopara viticola)

In France, the definition of appellations of origins is entrusted to the Institut National des Appellations d’Origine. (‘NAO). With the increase in price of appellations of origin vine­yards and considering the interests at stake, Institut National des Appellations d’Origine and the Institut National de Recherche Agronomique (INRA) established a work group in 1993 in order to study the “terroir-wine” relationship as precisely as possible, taking into account the knowledge acquired by researchers of the INRA and the experience in the field of the agents of the INAO.

The use of toasted vine-shoots as an alternative enological tool to make differentiated wines has generated interest among researchers and wineries. However, the evolution of these wines in bottle and the effect on the sensory profile has not been studied so far.

Cognac is a famous spirit produced in southwest France in the region of the eponymous town from wines mainly from Vitis vinifera cv. Ugni blanc. This variety gives very acidic and poorly aromatic base wines for distillation which are produced according to a very specific procedure. Grapes are picked at low sugar concentrations ranging 13-21 °Brix and musts with high turbidity (>500 NTU) are fermented without sulphite addition [1]. Fermentative aromas, as esters and higher alcohols, are currently the main quality markers considered in Cognac spirits.

As six on the nine planetary boundaries have already been crossed, putting our safe life on Earth at risk (Rockström et al., 2024) and agriculture is significantly responsible for it (Campbell et al., 2017), viticulture, faces the challenge of reducing its environmental impacts through fundamental changes to its practices.

All along the red winemaking process, many microorganisms develop in wine, some being beneficial and essential, others being feared spoilers. One of the most feared microbial enemy of wine all around the world is Brettanomyces bruxellensis. Indeed, in red wines, this yeast produces volatile phenols, molecules associated with a flavor described as “horse sweat”, “burnt plastic” or “leather”. To produce significant and detectable concentrations of these undesired molecules, the yeasts should first grow and become numerous enough. Even if the genetic group of the strain present and the cellar temperature may modulate the yeast growth rate¹ and thus the risk of spoilage, the main factor seems to be the wines themselves, some being much more permissive to B. bruxellensis development than others.