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California wine gets by with help from Brazilian friends
SAO PAULO, Brazil (Reuters) -- California wine growers are a step closer to tackling a deadly pest that is ravaging the state's vineyards, and they have Brazilian scientists to thank for it. At the request of the U.S. Department of Agriculture, a team of 30-odd researchers here has mapped the DNA code of Xylella fastidiosa, the bacteria that causes Pierce's disease and is threatening the livelihood of California's $2.7 billion wine and grape industry. While the discovery isn't enough in itself to save Chardonnay lovers from the threat of Pierce's disease just yet, it offers a complete blueprint of the bacteria's genetic make-up. That could provide new clues on how to stop its spread and, ultimately, find a cure. "This study is a huge step in the right direction," said Patrick Gleeson, executive director of the American Vineyard Foundation, a Napa Valley-based research group that donated $75,000 to the Brazilian study. Pierce's disease has long been a nagging problem for California wine growers, decimating vineyards in the Los Angeles basin as far back as the 1880s. Spread by sap-feeding insects known as sharpshooters, the disease blocks the flow of nutrients and kills vines within two years of infection. For nearly a century, growers managed to limit the damage caused by the disease -- which gets its name from the U.S. scientist who first identified it, Newton B. Pierce -- by using insecticides and lopping off infected shoots before it spread through the whole plant. More aggressive pestBut in the early 1990s, a new, more aggressive pest called the glassy-winged sharpshooter made its way to California from the southern United States, probably in a nursery shipment, and started to spread the disease with astonishing speed. Since the arrival of the glassy-winged sharpshooter, which is strong enough to feed on tougher stems that cannot be cut off without killing the vine, close to 6,000 acres of wine grape vineyards in California have been damaged by Pierce's disease, costing growers millions of dollars in lost revenue. The bug, which feeds and breeds on more than 130 plants, is also putting other key California crops at risk, including almonds, citrus, stone fruits and oleander. The threat is so big that federal, state and local governments have spent more than $65 million dollars since 1998 to fight the sharpshooter. "If you ask people in the wine industry here what their priorities are, Pierce's disease and the glassy-winged sharpshooter are at the top of the list," said Jay Van Rein of the California Department of Food and Agriculture, which has a $20 million annual budget to fund research and other projects aimed at controlling the disease. Desperate for a cure, the California wine industry and the USDA sought help in Brazil, a farming powerhouse that has made significant strides battling a similar disease that attacks citrus groves. Two years ago, a group of researchers in Sao Paulo state put Brazil on the scientific map by becoming the first anywhere to decipher the genome of a plant pathogen. After years of grueling laboratory work, they cracked the DNA of the strain of Xylella fastidiosa that causes a lethal disease in orange trees called Citrus Variegated Chlorosis, or CVC. Turning to BrazilThe news raised eyebrows across the globe, especially in California, where the glassy-winged sharpshooter was quickly turning Pierce's disease into a statewide problem. "Once the Brazilians tackled the genetics of CVC, the next logical step was to take advantage of their expertise to help solve our own problems," said Alexander Purcell, an expert on Pierce's disease at the University of California at Berkeley. Armed with a $500,000 budget, the Brazilians set out to compare the bacteria's strain that causes Pierce's disease with the one that attacks citrus trees, hoping to find similarities that could be exploited in the fight against both plagues. "What we discovered is that the Xylella that attacks grapevines is very similar to the Xylella that attacks citrus trees," said Mariana Cabral de Oliveira, a professor at the University of Sao Paulo's Bioscience Institute and co-coordinator of the study. "That means everything being done in Brazil to combat CVC can possibly be used in the struggle against Pierce's disease in California." The study, published in the February edition of the Journal of Bacteriology, also identified some potential weaknesses in the pest's metabolism, isolating genes that may help the bacteria attach to plant cells during colonization. Using similar knowledge of the make-up of CVC, scientists here have mutated a dozen links in the bacteria's genetic chain and are now scrambling to decipher which of the modified genes, when introduced into a citrus tree, stimulate the production of antibodies and make the plant immune to the disease. Now that the DNA of the strain that causes Pierce's disease has been mapped, scientists can finally conduct similar studies with grapes, speeding up the search for a cure. "What we've done is provide a shortcut for other scientists" studying Pierce's disease, said Marie-Anne Van Sluys, who directed the study. Copyright 2003 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
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