Identification of grapevine Pinot gris virus in free-living Vitis spp. located in riparian areas adjacent to commercial vineyards.

Grapevine Pinot gris virus (GPGV) is a recently identified pathogen of grapevines in California. To advance our knowledge about the epidemiology of GPGV, we investigated if free-living Vitis spp. can represent a source of virus infection. In 2019 a field survey of GPGV infection was conducted in Napa County. During the inspection 60 free-living vines in riparian habitats near commercial vineyards with GPGV infection were sampled. Samples were tested by real-time reverse transcription PCR (RT-PCR), identifying 23 free-living Vitis spp. positive for GPGV. Later, GPGV infection was confirmed in these plants via end-point RT-PCR and Sanger sequencing. Based on sequence analysis, detected GPGV isolates are more related to the asymptomatic variant of the virus. Vitis species ancestry was determined by DNA fingerprinting. GPGV-infected material included V. californica, V. californica × V. vinifera hybrids and hybrid rootstock cultivars. Here, GPGV is reported for the first time in free-living Vitis spp. The results of this study will support the development of management strategies for GPGV in California and beyond.