Current UC Viticulture Research

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The vineyard is approximately seven acres of Cabernet franc on nine virus-inoculated rootstocks .

Principal Investigator	Adib Rowhani
Project Title	Grapevine Leafroll Disease, A General Detail Study and Evaluation
Funding Agencies	American Vineyard Foundation
Summary	Grapevine leafroll disease causes poor color development in red grape varieties and non-uniform maturation of fruit in Vitis vinifera. It also has been reported to cause a delay in fruit maturation of 3 to 4 weeks, and crop loss as high as 20-40%. To date, 11 different viruses, named Grapevine leafroll associated virus (GLRaV) types -1 to -7, -9, -10, -11 and a newly discovered virus from a Carnelian clone which tentatively has been named GLRaV-Car are proven to be associated with leafroll disease. This project studies the effects of GLRaV types -1 and -2 (2 isolates each), -3 (3 isolates), -4, -5, -7 and -9 (one isolate each) and a combination of two of types -1, -2, -3, -5 and -7 on Cabernet Franc grafted onto 9 different rootstocks. The rootstocks used are: AXR #1, Mgt 101-14, 110R, 3309C, 5BB, 420A, Freedom, St. George 15 and St. George 18. There are 15 replicates for each treatment in three different blocks (5 replicate per treatment per block). 2011 data showed that the virus isolate LR132 (a mixed infection of GLRaV-1 and Grapevine virus A) had unfavorable effects on Cabernet Franc plants grafted to 420A, Freedom, 3309C and 101-14 rootstocks, and many of these plants died just a few months after inoculation. It is not clear whether a certain strain of GLRaV-1 is the cause of poor vine performance, or the presence of GVA creates a synergistic effect and kills the plants. It was also found that the presence of GLRaV-2 had harmful reactions on vines propagated on Freedom and 5BB. These vines were weak - almost dying - and exhibited red leaf symptoms and short internodes. Different GLRaV types produced leaf symptoms of different severity; for example, it was observed that leaf symptoms produced by GLRaV-3 were more severe than by GLRaV-4. This research project should provide useful information in regards to the effects of single and double infection of viruses associated with leafroll disease on vine performances, yields components, fruit composition and quality, and virus detection. Refining the leafroll virus detection methods proposed in this project will improve the testing scheme used in grapevine certification programs, and the data will provide information useful for growers/vintners in decision making and vineyard management.
Supplemental Data	Figure 1. Symptom ratings are shown on each panel based on their severity on Cabernet Franc. Table 1. Shows the effects of isolate LR132 which is a mixed infection of GLRaV-1 and GVA on different rootstocks. Table 2. Shows the effects of the mixed inoculation of isolates LR132+LR101, which included mixed virus infection of GLRaV-1, -3 and GVA. Table 3. Shows the effects of the mixed inoculation of isolates LR132+LR133, which included mixed virus infection of GLRaV-1, -5 and GVA. Table 4. Shows the symptom severity comparison between isolates LR106 (GLRaV-4) and PA94.148 (GLRaV-3). Table 5. Shows the effects of GLRaV-2 (isolates LR103 and LR119) on rootstocks Freedom and 5BB.
Researchers and Cooperators	Deborah Golino Adib Rowhani Susan Sim Nick Dokoozlian Fatima Osman
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. 1992. The Davis Grapevine Virus Collection. American Journal of Enology and Viticulture 43(2):200-205. Abstract Golino, D.A., Sim, S.T., Bereczky, J. and Rowhani, A. 2001. The Use of Shoot Tip Culture in Foundation Plant Materials Service Programs. Combined Proceedings of the International Plant Propagators Society, Volume 50:568-573. Golino, D.A., Sim, S.T., Weber, E. and Rowhani, A. 2008. Leafroll disease is spreading rapidly in a Napa Valley vineyard.(pdf) California Agriculture 62(4):156-160. Osman, F., Leutenegger C., Golino D. and Rowhani, A. 2008. Comparison of low-density arrays, RT-PCR and real-time TaqMan RT-PCR in detection of grapevine viruses. J Virol Methods149(2):292-9. Epub 2008 Mar 10. Osman, F., Leutenegger C., Golino D. and Rowhani, A. 2007. Real-time RT-PCR (TaqMan®) assays for the detection of Grapevine Leafroll associated viruses 1–5 and 9 (pdf). J Virol Methods 141:22-29. Rowhani, A., 1992. Use of (ab)2 antibody fragment in ELISA for detection of grapevine viruses. Am. J. Enol. Vitic. 43:38–40. Abstract Rowhani, A., Biardi, L., Johnson, R., Saldarelli, P., Zhang, Y.P., Chin, J., Green, M., 2000. Simplified sample preparation method and one-tube RT-PCR for grapevine viruses. In: Proceedings of XIII International Council for the Study of Viruses and Virus-Like Diseases of the Grapevine, Adelaide 2000,p. 82. Rowhani, A., Uyemoto, J.K., Golino, D., and Martelli, G.P. 2005. Pathogen testing and certification of Vitis and Prunus species (pdf). Annual Review of Phytopathology 43: 261-278. Tsai, C., Rowhani, A., Golino, D., Daane, K., and Almeida, R. 2010. Mealybug Transmission of Grapevine Leafroll Viruses: An Analysis of Virus–Vector Specificity (pdf). Phytopathology 100(8): 830-834.