Résumé
Wine production is a complex process that depends on both climatic conditions and practices in the vineyard and winery. The microbiological component plays a crucial role in the transformation of must into wine, and the release of aromas that contribute to the organoleptic quality of wines. Today's societal demand is moving towards less standardized wines with more complex aromas, while at the same time demanding a reduction in inputs for a more environmentally friendly agriculture. Grape varieties resistant to mildew and powdery mildew make it possible to reduce the use of phytosanitary products in both conventional and organic farming systems, providing a solution to the health and environmental concerns associated with the use of fungicides. Meanwhile, wines made by spontaneous fermentations suing indigenous flora, are gaining popularity. Opting for spontaneous fermentations, which aim to harness and preserve natural biodiversity, requires a deep understanding of microbial communities and their impact on fermentation and wine quality.The aim of our project is to study the microbiota of resistant grape varieties in comparison to conventional Vitis vinifera cultivars and to decipher the influence of biotic and abiotic factors on the microbiota composition. The effects of “terroir”, vintage, vine treatment, grape variety or agro-ecological environment were estimated. Various viticulture systems were used: conventional, organic and absence of treatment. Grapes of resistant hybrid and traditional cultivars were harvested from experimental plots set up on different INRAE agricultural devices. The microbiota on the grape surface and at different time-points of spontaneous fermentations were analyzed using a metabarcoding approach. The relative abundance and diversity of yeast and fungal genera were compared and the relative impact of different parameters were estimated. The strongest effect on microbiota diversity was linked to geographical region, probably due to abiotic factors such as climate and soil. No statistical differences were observed between the microbiota of varieties cultivated in different viticultural systems. However, in each experimental device, cultivars were distinguishable, suggesting an influence of grape variety on the microbial community of the grape berry surface. The impact of microbiota on the aromatic quality of wines made from indigenous fermentations was also assessed through microfermentations.