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34 WINES&VINES September 2015 Vineyard View S ome readers may be surprised at the head- line of this column, because they have the impression grapevine red blotch-associ- ated virus is a new disease. I borrowed it from a presentation by Dr. Deborah Go- lino, director of Foundation Plant Services (FPS) at the University of California, Davis. The wording is deliberate, because the goal of her talk was to let grow- ers and winemakers know—once and for all—that the disease has been with us for a very long time. We just did not have the tools to identify it. Despite Golino presenting this information to hun- dreds—if not thousands—of wine industry stakeholders, misunderstandings still appear to exist in some quarters. So the purpose of my column is to continue the hard work of disseminating the red blotch message to the wine industry. Prehistoric red blotch? Normally I would start with some basic facts about what red blotch looks like and how it impacts grapevines and wine. However, I'll instead present a fact that seems to get lost in the chaos surrounding red blotch disease: Evi- dence gathered about where grapevine red blotch associ- ated virus came from indicates the disease co-evolved with the grape. There are several reasons for this conclu- sion. First, it has been found in all of the major grape- growing regions in the United States and Canada. (Interestingly, the French are keeping noticeably quiet about red blotch.) Second, it can infect all types of grapes, including red and white wine grape varieties, table grapes, raisin grapes and grape rootstocks. And finally, it was recently found in a herbarium specimen collected by Harold Olmo in Sonoma County, Calif., in 1940. That's 72 years before GRBaV was conclusively identified using the latest genetic techniques! How could we have missed it for so long? Because its symptoms vary consider- ably, and they are easily mistaken for those caused by leafroll virus. So until 2008 no one thought to look for something different. That year Jim Wolpert (at that time viti- culturist at UC Davis) noticed some- thing a little different about red, blotchy symptoms on some v i n e s g r o w i n g i n t h e Oakville Station research vineyard in Napa Valley. It then took virologists until 2012 to verify through sophis- ticated DNA analyses that they were dealing with an unknown virus. Subsequently, a polymerase chain reac- tion (PCR) test was developed to identify grapevine red blotch-associated virus, so grape tissues from vineyards suspected to host the virus could be tested. One thing I believe makes red blotch disease a difficult problem for growers and winemakers to understand is that grapevine red blotch associated virus (GRBaV) is a DNA virus. It infects a host cell by insert- ing its DNA into the host cell DNA and basically taking over the cell's machinery, which then begins to make new virus par- ticles. The new virus particles leave the cell—destroying it in s o m e c a s e s — a n d they enter new cells, starting the virus particle-making process all over again. Once the virus DNA is inserted into grape cell DNA, the vine is never free of the disease. Another way that viruses are different from other disease-causing agents is how they are named. GRBaV is not only awkward to type, I find it awkward to read, too. At first, after viruses were identified as organisms, they were named according to the hosts they infected and the symptoms they caused. Thus we have names like grape leafroll virus. Finally, in 1971 an international committee on virus taxonomy began to standardize virus classification, giving rise to the naming protocols in use today. Thus, grapevine red blotch associated virus was named GRBaV. How is it spread? More recently, genetic sequencing has allowed virologists to construct virus family trees in a very accurate way. They now know that GRBaV is related to viruses in the Geminiviridae family, although it is on a family branch all by itself. Other viruses in the family infect vegetables, field crops, ornamental plants and papaya. This taxonomy is important because the other groups in this family can all be vectored by insects, with each group apparently vectored by one n CLIFF OHMART Red Blotch Disease: a Long and Winding Road Evidence gathered about where grapevine red blotch associated virus came from indicates the disease co-evolved with the grape.