Survey for Possible Reservoirs for Leafroll Viruses in North Coast
In out initial survey we detected Grapevine virus A (GVA) and /or Grapevine leafrollassociatedvirus 3 (GLRaV-3) in V. californica and V. californica x V. vinifera hybrids in the non-cultivated areas adjacent to three Napa Valley vineyards with leafroll disease symptoms. In addition, we identified Grapevine leafroll-associated virus 2 (GLRaV-2), GLRaV-3, GVA and/or Grapevine virus B (GVB) in V. californica and V. californica x V. vinifera hybrids in three riparian areas not near vineyards. This establishes that noncultivated Vitis spp. hosts for these leafroll and vitiviruses exist. Since our samples numbers were low, we returned to the three vineyards and two of the three riparian areas with positive V. californica and V. californica x V. vinifera hybrid samples and collected and additional 185 non-cultivated Vitis spp. and V. vinifera. We are currently testing these samples for GLRaV-2, GLRaV-3, GVA and GVB. When testing is complete, we will be able to estimate incidence at these sites. We also included two new vineyards with known GLRaV-2 and GLRaV-3 infections in order to extend our survey area to the more northern and southern regions of Napa County. All of the V. californica, V. californica x V. vinifera hybrids, and willow samples were negative. The material for biological assays has been collected.