Diversity of microscopic fungi colonizing grapevines affected by grapevine trunk diseases in Slovak wine-growing region

Grapevine trunk diseases pose a significant global threat, with detrimental impacts on grapevine health and productivity. The aim of the study was to assess and compare the fungal diversity colonizing the trunks of symptomatic and asymptomatic grapevines in two wine-growing villages in southwestern Slovakia. Microbiological analyses on the grapevine wood sections were conducted using the amputated parts of the grapevine trunks. Wood sawdust was extracted from the trunks, cultured on malt extract agar, and incubated at 22 °C without light. The fungal species affiliation was identified using the universal primers ITS1F and ITS4 and sequenced by the Sanger method. In Nitra, a total of 103 microscopic fungal isolates, representing 32 Operational Taxonomic Units (OTUs), were obtained, with Diplodia mutila being the most prevalent species. The genus Diplodia, associated with the Botryosphaeria dieback complex, constituted 29.1% of all isolates from grapevine trunks. In Vráble, 101 fungal isolates were recovered, representing 34 OTUs, with Seimatosporium vitis emerging as the most prevalent fungal species. Eutypa lata , a species associated with the Eutypa dieback complex, occurred in both localities. Fungal species from the Grapevine trunk diseases complex colonized both symptomatic and asymptomatic grapevines. Although the species and genus counts showed a similar quantitative distribution between sites, only 31.5% were common to both localities. Differences in fungal diversity were observed between the experimental localities, highlighting the regional variations in the fungal communities that colonize the grapevine trunks. The results contribute to worldwide approaches to determine the causes and identify the primary triggers of Grapevine trunk diseases.