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February 2016 WINES&VINES 21 WINE INDUSTRY NEWS D avis, Calif.—Scientists may not under- stand what's behind the recent outbreak of Pierce's disease in grapegrowing regions along California's North Coast, but the research lab of professor Abhaya Dandekar, Ph.D., at the University of California, Davis, recently identified an enzyme that allows the bacterial pathogen to persist and infect new grapevines. The authors of a paper published last month in Scientific Reports explain that Xylella fastidiosa (Xf), the bacteria responsible for Pierce's disease, was long believed to block the xylem that carry water to the leaves of grape- vines, causing them to turn brown and die. But when researchers in Dandekar's lab inspected leaves showing symptoms of Pierce's disease, they didn't always find a large Xf presence in symptomatic tissues. Conversely, some healthy, green leaves contained large amounts of Xf without showing the characteristic browning symptoms of Pierce's disease (PD). Reviewing this information, "We decided maybe the bacteria was secreting something that allowed those cells to die," Dandekar told Wines & Vines. Using a new type of technology that identifies proteins and en- zymes, researchers noticed one protein that appeared in large concentrations in grapevine leaves browned by PD—an enzyme they later named LesA. The group found that LesA was able to break down lipids (or fats) that provide nutrition to Xf, which also benefitted from nutri- ents released during the death of grapevine leaves. With funding from the Pierce's Disease Board, graduate students Rafael Nascimiento and Hossein Gouran decided to take their discovery one step further, and in 2013 experimented with knocking out genes responsible for LesA. "When we knocked that gene out, we could see that Xylella was less able to cause a dis- ease," Dandekar told Wines & Vines. The revelation leads to a new question Dan- dekar hopes to study: Is there a way to block the enzyme from being released or providing nutrition to Xf? Xylella fastidiosa "derive nutrition from the fats that this enzyme can break down, so that adds a new wrinkle to investigate," he said. Another avenue to re- search, Dandekar says, is how the protein is related to the persistence of Xylella fastidi- osa. Understanding "the abil- ity for this bacteria to hang out in the environment will improve how we can eradicate it," he said. Strains of the Xylella bacte- ria are known to cause disease in plants ranging from citrus, pear and olive trees to oleander and coffee. Understanding the protein's activity could have wide-reaching effects with other crop-scorching diseases. "This gene is highly common in that and has some similar activities," Dandekar told Wines & Vines. "If we take this protein and inject it into plants, we see this scorching-like symptom" common among Pierce's disease- afflicted vines. —Kate Lavin Scientists Identify Enzyme Feeding Pierce's Disease Researchers identified the enzyme that allows Xyllela fastidiosa to spread Pierce's disease in grapevines. AARON JACOBSON/UC DAVIS Simplify and accelerate barrel cleaning without compromising cleaning effectiveness with the new TankJet M60 barrel cleaner. • It's mobile, so it is quick and easy to position right next to the barrel, insert into the bung hole, clean and move to the next barrel • Powerful, fast cleaning at low fl ow rates prevents toast removal – clean multiple barrels in minutes • Non-lubricated air motor ensures speed and cycle times are relatively constant even when liquid pressure changes • Compatible with a variety of pressure washers and pumps INTRODUCING THE TANKJET ® M60 MOBILE BARREL CLEANER: EASIER, FASTER & BETTER CLEANING FREE TRIAL OR ON-SITE DEMO CALL 1.800.95.SPRAY TO SPEAK WITH YOUR LOCAL REP OR VISIT TANKJET.COM TankJet M60 barrel cleaner – effective cleaning of barrels up to 5' (1.5 m) in dia.