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GRAPEGROWING Red Blotch Slows Vine Supply Virus has become a serious issue for grapevine nurseries By Paul Franson A • urseries report doing extensive testing N for red blotch but still lack sufficient vines certified to be virus free. • s a result, there is a shortage of A acceptable vines in certain varieties and rootstocks. 56 W in e s & V i ne s F E B R uary 20 14 ARS • any wine grape growers are demanding M virus-free vines, especially red blotchfree, as they replant and add acreage. USDA- Highlights M.R. Sudarshana, year ago grape growers and wineries feared that a shortage of grapevines from commercial nurseries could impact their replanting efforts, but nurseries assured them they'd have plenty of vines to plant by now. Red blotch virus has changed all that. The troublesome virus has become a priority issue, and the demand for vines free of the infection has caused a new setback for some nurseries trying to fill growers' orders. "Red blotch has pushed deliveries back to 2015 and 2016 for many vines," said Michael Monette of Sunridge Nurseries in Bakersfield, Calif. "We were already juggling vines because of leafroll virus, and now every customer demands vines free of red blotch." The National Clean Plant Network (NCPN) at Foundation Plant Services based at the University of California, Davis, has developed strict "Protocol 2010" standards that confirm the absence of many plant pathogens including viruses. To qualify as Protocol 2010 plant material, the vines must have been created using micro-shoot tip culture and tested for an extensive list of pathogens. This process can take several years. Vines that meet the Protocol Tests can identify presence of the virus in vine tissue such as leaf, petiole, dormant canes or clusters. 2010 standards are planted in the primary NCPN foundation collection at Russell Ranch, near Davis, Calif. To date, however, only a limited number of plants have been available to nurseries for commercial-scale propagation. The first vines to qualify for Protocol 2010 vines were rootstocks planted in 2011. There are now more than 1,000 vines planted at Russell Ranch that are starting to produce plant material for grapevine nurseries. Until the supply of new plant materials from the NCPN ramps up to the level they need, the nurseries will continue using their own strategies to deliver virus-free vines. Sunridge manager Steve Maniaci said, "We have tested and found absolutely zero red blotch-positive vines in our Bakersfield certified increase blocks." The company won't accept scion wood for grafting unless it's certified, he added. At Duarte Nursery in Hughson, Calif., one of the largest grapevine suppliers, John Duarte said, "There is a high demand for vines that are certified free of red blotch. We are propagating and supplying vines that are red blotch tested and clean. The supply of vines is sufficient, but we have a few rootstock varieties where we cannot accept further commitments. We have many that we can offer for spring 2014 delivery." Novavine in Santa Rosa, Calif., also provides red blotch-free vines. "We're testing a lot of material," said Novavine's Sam Caselli. "Red blotch likes to hide," he said. "We've had to readjust. A lot of orders were affected by the new demand for vines clean of red blotch." About red blotch The symptoms of red blotch disease— more formally, grapevine red blotch associated virus (GRBaV)—were first described in 2008, and transmission by grafts was confirmed in 2012, according to Dr. Marc Fuchs of the Department of Plant Pathology at Cornell University in