A Local Microbiome Survey of Vineyards Representative of the Barbera d’Asti Wine Territory

Background Agricultural practices can impact the complex interactions between soil, plant and microorganisms, modifying soil fertility and crop resilience to various stresses. In the case of grapes, soil microbiome can also affect the winemaking process, the wine’s final quality and the terroir’s definition. Methods and Results In this study, the soil microbiome of 11 vineyards representative of the various production areas of the Barbera d’Asti protected denomination of Piedmont (Italy) was studied using amplicon sequencing of 16S V4, ITS1 and ITS2 gene regions of bacteria, archaea and fungi, respectively. Besides comparing biodiversity indices for the vineyards, the taxonomic composition at the phylum level and the core microbiome features were analysed, identifying the taxa differently characterising the Barbera d’Asti terroir. Actinobacteriota and Ascomycota were the two most abundant phyla for bacteria and fungi, respectively. Beta diversity indices performed better than alpha diversity indices in distinguishing the vineyards. The taxonomic composition of the fungal communities at the class level was able to discriminate the vineyards identifying three groups. The relative abundances of various bacterial and fungal phyla were highly related with the vineyard features (soil physicochemical properties and topographic and climatic conditions). Annotated fungal OTUs were assigned to six functional guilds, four of which were consistently present in both quantity and diversity levels in all vineyards, with the following common pattern: Mycorrhizal < Endophytes < Saprotrophs < Pathogens. Significance of the Study The analysis of the soil metagenome provided new insight into the complexity of the soil microbiome in this production area characterised by diverse soils, highlighting the impact of pedoclimatic factors on the soil microbiome structure and functionality. The results could support current efforts for the definition of specific terroirs or subzones of the Barbera d’Asti wine, suitable for the valorisation of the protected denomination.