Epiphitic Microbiome of Alvarinho Wine Grapes from Different Geographic Regions in Portugal

SIMPLE SUMMARY: Wine, the product of biological activity on grape must, is much more than a simple product of fermentation. In fact, its relevance is manifested through cultural and social impacts, and it is, in many cases, a factor of economic development and fundamental regional/local identity. Alvarinho monovarietal wine is an example of this, as it is originally from the sub-region of Monção and Melgaço in the North of Portugal. The characteristics of a wine are highly influenced by several factors, including the microbial flora present on the surface of the grapes. This microbiota will contribute to the terroir associated with a given region in the production of wine, allowing the creation of wines with specific characteristics and greater typicality. The microbiome present on the surface of Alvarinho grapes was analyzed by High-Throughput Sequencing, and the results allowed for the determination of a core microbiome associated with grapes from any of the analyzed regions. The results made it possible also to verify that the α-diversity (for fungi) of the microbial population of the grapes from the region where the Alvarinho variety is native is different, with a yeast of the genus Metschnikowia, which is described as having enological potential in the creation of fresh and fruity wines, ubiquitously present in all plots of Monção and Melgaço. ABSTRACT: Geographic location and, particularly, soil and climate exert influence on the typicality of a wine from a specific region, which is often justified by the terroir, and these factors also influence the epiphytic flora associated with the surface of the grape berries. In the present study, the microbiome associated with the surface of berries obtained from ten vineyards of the Alvarinho variety located in different geographical locations in mainland Portugal was determined and analyzed. The removal of microbial flora from the surface of the berries was carried out by washing and sonication, after which the extraction and purification of the respective DNA was carried out. High-throughput short amplicon sequencing of the fungal ITS region and the bacterial 16S region was performed, allowing for the determination of the microbial consortium associated with Alvarinho wine grapes. Analysis of α-diversity demonstrated that parcels from the Monção and Melgaço sub-region present a significantly (p < 0.05) lower fungal diversity and species richness when compared to the plots analyzed from other regions/sub-regions. The ubiquitous presence of Metschnikowia spp., a yeast with enologic potential interest in all parcels from Monção and Melgaço, was also observed.