Pruning wound protection products induce alterations in the wood mycobiome profile of grapevines.
Fungal pathogens involved in grapevine trunk diseases (GTD) may infect grapevines throughout their lifetime, from nursery to vineyard, via open wounds in stems, canes or roots. In vineyards, pruning wound protection products (PWPP) offer the best means to reduce the chance of infection by GTD fungi. However, PWPP may affect non-target microorganisms that compose the natural endophytic mycobiome residing in treated canes, disrupting microbial homeostasis and indirectly influencing grapevines health.  Using DNA-metabarcoding, we characterized the endophytic mycobiome of one-year-old canes of cvs. Cabernet Sauvignon and Syrah in two vineyards, in Portugal and Italy, and assessed the impact of established and novel PWPP on the fungal communities of treated canes.  Our results reveal a large fungal diversity (176 taxa), and we report multiple genera never detected before in grapevines wood. We found differences in mycobiome beta diversity when comparing vineyards (p=0.01), but not cultivars (p>0.05). When examining PWPP-treated canes, we detected cultivar- and vineyard-dependent alterations in both alpha and beta diversity. In addition, numerous fungal taxa were over- or under-represented, when compared to control canes. Among them, Epicoccum, a beneficial fungus with biological control potential, was negatively affected by selected PWPP. This study demonstrates that PWPP induce alterations in the fungal communities of grapevines, requiring an urgent evaluation of their direct and indirect effects on plants health, to better advise viticulturists and policy-makers.