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A recently described putative foveavirus, grapevine virus T (GVT), was detected in a Slovak grapevine accession (SK704) using high-throughput sequencing, prompting further studies. Full-length genome sequence of isolate GVT-SK704 was determined. Analyses revealed 86.1% nucleotide identity with the Italian GVT isolate, currently the only available nearly complete sequence of GVT in GenBank. A virus-specific RT-PCR assay was developed, which enabled a survey of GVT incidence in grapevine samples from Slovakia and Czech Republic. Unexpectedly, GVT was present in ~ 30% of tested samples. Analysis of complete CP gene sequences of 20 Slovak and Czech GVT isolates detected in the survey revealed relatively high intra-species variability (up to 11.2% nucleotide divergence), suggesting multiple introductions from different sources, possibly over an extended period of time.

Grapevine Syrah virus-1 (GSyV-1) was identified by small-RNA deep sequencing in Slovak grapevine co-infected by several other viruses. The RT-PCR assays developed in this work substantially improved the virus detection and allowed the identification of GSyV-1 in tested grapevine samples from Slovakia and the Czech Republic at an unexpectedly high rate (ca. 30 %). Subsequently, complete genome sequences of 3 GSyV-1 isolates (2 Slovak and 1 Czech) were determined by Sanger sequencing, showing a typical marafivirus genome organization. Analyses of complete genome sequences showed a higher intra-group diversity among these 3 central European GSyV-1 isolates (differences reaching 7.1 % at the nucleotide level) in comparison to 3 previously characterized North American isolates (only 1.2 % intra-group divergence). A substantially higher divergence among central European isolates and their clustering into two major phylogenetic groups was further confirmed by the partial genome analysis of additional 26 isolates. The CP-centered study did not support the geography-based clustering among central European and American isolates. Nevertheless, the sequence data of the highly variable 5'-proximal portion of the genome obtained for few additional isolates from Slovakia and Czech Republic showed the presence of both, "European-" and "north American-like", GSyV-1 isolates in the analyzed grapevine samples.