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Collecting samples of wild Vitis adjacent to a Napa County vineyard.

Principal Investigator	Deborah Golino
Project Title	Survey for Possible Reservoirs for Leafroll Viruses in North Coast Vineyards
Funding Agencies	American Vineyard Foundation
Summary	This project addresses concerns about potential reservoirs of virus in plants other than cultivated grapevines that might be an important factor in the epidemiology of grapevine leafroll disease. Samples were collected of 83 wild grapes (Vitis spp.) and 85 non-Vitis weed, cover crop and native species found in and near nine vineyards symptomatic for leafroll disease, and tested for grapevine leafroll associated viruses (GLRaV) 1-5, 7, and 9, and vitiviruses GVA, GVB, and GVD. Wild Vitis samples were also collected from two habitats distant from vineyards to assess virus incidence in a natural environment. The wild Vitis spp. genotypes were determined by DNA fingerprinting, and the genotypes were then analyzed and grouped into three categories: V. californica, V. vinifera hybrids, and wild V. vinifera plus rootstock cuttings. We detected GLRaV-2, GLRaV-3, GVA, and GVB in all three groups of wild Vitis. Overall virus incidence was 27 percent, but percent infection differed depending on the genotype. At least one of the four viruses was detected in: 18% of the V. californica samples, 48 percent of the V. vinifera hybrids; and 100 percent of the wild V. vinifera plus rootstock cuttings. Viruses were detected in wild Vitis spp. in habitats both near to and distant from vineyards. Preliminary evidence indicates that there is no correlation between virus infection in vineyards and in nearby wild Vitis spp. Our sample size was small, however, and further sampling is needed. An ornamental grapevine, ‘Roger’s Red,’ was included in our samples. It is grown for its red fall foliage and was previously thought to be V. californica. Roger’s Red tested positive for GLRaV-2 and GVB. DNA fingerprinting indicated that it is a hybrid of V. californica x V. vinifera ‘Alicante bouschet’. Alicante bouschet is a tintureiro variety known to have red leaves in the fall. Both the virus infection and genetic background could account for its red leaves in the fall. This survey establishes that wild Vitis spp. are hosts for two of the most important leafroll-associated viruses, GLRaV-2 and -3, in addition to GVA and GVB. This is the first evidence of a leafroll virus in a woody host besides Vitis spp. and has important implications for leafroll disease management.
Supplemental Data	Table of virus test results of plant species collected Project photos: click thumbnail to view full-sized image. Wading to collect wild Vitis samples. Determining GPS coordinates of samples.
Links	Survey of Wild Grape, Weed, and Cover Crop Species for Grapevine Viruses- Short videotaped presentation by Deborah Golino, Department of Plant Pathology/Foundation Plant Services, UC Davis, at the Wine and Wine Grape Research 2010 seminar February 18, 2010 at UC Davis. Video recording was done by UC ANR Communication Services.
Researchers and Cooperators	Deborah Golino Adib Rowhani Susan Sim Vicki Klaassen
Publications	Dangl, G.S., Raiche, R., Sim, S., Yang, J., and Golino, D.A. 2010. Genetic Composition of the Ornamental Grape Roger’s Red. Am. J. Enol. Vitic. 61(2):266-271. Abstract Golino, D.A. and Almeida, R. 2008. Studies needed of vectors spreading leafroll disease in California vineyards.(pdf) Sidebar. California Agriculture 62(4):174. Golino, D.A., Sim, S.T., Osman, F., Aldamrat, R., and Rowhani, A. 2009. Grapevine viruses detected in wild grapes (Vitis californica). Phytopathology 99: S44. http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.2009.99.6.S1 Golino, D.A., Sim, S.T., Osman, F., Aldamrat, R., Klaassen, V., Rowhani, A. 2009. Survey of wild grapes, weed and cover crop species for grapevine viruses. Progrès Agricole et Viticole, p. 110-111. http://www.icvg.ch/archive.htm Golino, D.A., Weber, E., Sim, S., and Rowhani, A. 2008. Leafroll disease is spreading rapidly in a Napa Valley vineyard.(pdf) California Agriculture 62(4):156-160. Klaassen, V.A. 2009. Discussions from Grapevine Leafroll Symposium 2.0. Foundation Plant Services Grape Program Newsletter. p. 13-16. http://fps.ucdavis.edu/WebSitePDFs/Newsletters&Publications/GrapeNewsletter2009.pdf Klaassen, V. 2010. Leafroll Disease Research at FPS (pdf). FPS Grape Program Newsletter, Foundation Plant Services, University of California, Davis. October 2010, p. 16. Klaassen, V. A., Sim, S. T., Dangl, G. S., Osman, F. A., Al Rwahnih, M., Rowhani, A., and Golino, D. A. 2011. Vitis californica and Vitis californica x Vitis vinifera hybrids are hosts for Grapevine leafroll-associated virus-2 and -3, and Grapevine virus A and B. Plant Disease 95 (in Press). Tsai, C.-W., Rowhani, A., Golino, D.A., Daane, K.M., and Almeida, R.P.P. 2010. Mealybug transmission of grapevine leafroll viruses: An analysis of virus–vector specificity. Phytopathology 100: 830-834.