Grape berry mycobiota and its contribution to fresh mushroom aroma off-odour in wine

Grape berry mycobiota is a complex and diverse ecosystem that is constantly evolving during the different berry ripening stages of vines, as well as in musts and wines, which can ultimately impact wine sensorial properties and thus overall product quality. To better characterise the role of this mycobiota in wine off-odours, we studied for the first time changes in Pinot Noir and Meunier grape and must mycobiota and carried out sensorial analyses in the resulting wines, with a focus on fresh mushroom aroma. Grapes from three berry ripening stages, fruit set, veraison and harvest, were collected without sorting bunches from 31 parcels, then laboratory-scale grape crushing was performed to obtain musts, followed by micro-winemaking. For all sample types, both culture-dependent and -independent strategies were used to decipher both species and genus level mycobiota composition. After the winemaking process, sensorial analyses detected 9 laboratory wines with fresh mushroom aroma off-odours. Musts that generated these spoiled wines contained higher total fungal counts, especially Penicillium spp., compared to other musts. A total of seven Penicillium species, including one unidentified Penicillium sp., was detected using the culture dependent approach; this genus represented up to 100 % of all fungal counts in musts linked to FMA wines. Fungal interactions inferred using co-occurrence networks revealed positive interactions between Vishniacozyma, Cladosporium and Penicillium in musts, indicating the possible implication of these three genera in FMA production. Negative interactions were observed in musts between the two yeast genera, Starmerella and Pichia, with Penicillium, Botrytis, Vishniacozyma and Cladosporium, as well as between Metschnikowia with Botrytis and Vishniacozyma. Starmerella, Pichia and Metschnikowia may thus be potential biocontrol candidates for use against Botrytis and Penicillium grape contamination.