Metagenomic Assessment Unravels Fungal Microbiota Associated to Grapevine Trunk Diseases

Grapevine trunk diseases (GTDs) are among the most important problems that affect the longevity and productivity of vineyards in all the major growing regions of the world. They are slow-progression diseases caused by several wood-inhabiting fungi with similar life cycles and epidemiology. The simultaneous presence of multiple trunk pathogens in a single plant together with the inconsistent GTDs symptoms expression, their isolation in asymptomatic plants, and the absence of effective treatments make these diseases extremely complex to identify and eradicate. Aiming to gain a better knowledge of GTDs and search sustainable alternatives to limit their development, the present work studied the fungal community structure associated with GTDs symptomatic and asymptomatic grapevines, following a metagenomic approach. Two important cultivars from the Alentejo region with different levels of susceptibility to GTDs were selected, namely, ‘Alicante Bouschet’ and ‘Trincadeira’. Deep sequencing of fungal-directed ITS1 amplicon led to the detection of 258 taxa, including 10 fungi previously described as responsible for GTDs. Symptomatic plants exhibited a lower abundance of GTDs-associated fungi, although with significantly higher diversity of those pathogens. Our results demonstrated that trunk diseases symptoms are intensified by a set of multiple GTDs-associated fungi on the same plant. The composition of fungal endophytic communities was significantly different according to the symptomatology and it was not affected by the cultivar. This study opens new perspectives in the study of GTDs-associated fungi and their relation to the symptomatology in grapevines.

This research was supported by Portuguese National Funds through FCT- MCTES under the PhD scholarship SFRH/BD/145321/2019, attributed to M.P., co-financed by the European Social Fund through the Regional Operational Program of the Alentejo. It was also supported by the project “Control of olive anthracnose through gene silencing and gene expression using a plant virus vector” (ALT20-03-0145-FEDER-028263 and PTDC/ASP-PLA/28263/2017) and by the project “Development of a new virus-based vector to control TSWV in tomato plants” (ALT20-03- 0145-FEDER-028266 and PTDC/ASP-PLA/28266/2017), both projects co-financed by the European Union through the European Regional Development Fund, under the Alentejo 2020, Algarve 2020 and through the FCT, in its national component.