The epiphytic grapevine microbiome is shaped by a variety of variables at various geographical scales, including biogeography, cultivar, and vintage.

Abstract

Microbial terroir is established by a variety of variables that influence the makeup of the grapevine microbiome. Less is known about the assembly processes of the epiphytic grapevine microbiome, while the majority of research has concentrated on the grape must microbiome. Our goal was to separate the effects of cultivar, vintage, and geographic location on the epiphytic fungal and bacterial populations of grapevine, both within (regional scale) and across (national scale) Greek viticultural zones. We postulated that: (i) these three variables have varying effects at various geographical scales; and (ii) bacteria and fungus react differentially to the factors influencing the grapevine microbiome. We examined leaves and berries from Greek cultivars (i) Vidiano and Agiorgitiko, which are found in three geographically separated areas (ranging from 100 to >600 km), and (ii) Roditis and Sideritis, which are found in several terroir units within the Aigialeia viticultural zone. Findings: While cultivar becomes a significant driver at the viticultural zone scale, amplicon sequencing study revealed substantial regional characteristics on the epiphytic microbiota across viticultural zones. Compared to bacterial communities, fungal colonies responded better to every factor examined. Differential abundance (DA) analysis revealed dominant amplicon sequence variants (ASVs) of bacteria (Sphingomonas, Masillia, Streptococcus, Staphylococcus, Enterobacterales) and fungi (Alternaria, Cladosporium, Nigrospora, Aureobasidium, Vishniacozyma) that showed patterns specific to cultivar and geography. In conclusion, our findings indicate that the epiphytic grapevine microbiome is shaped by several causes at various geographical scales, with fungal and bacterial populations exhibiting distinct reactions to the structural features under investigation.