|Office of the Chancellor / Public Affairs||
Tuesday, June 22, 2004
Sacramento Bee 6-22-04
In search of a fighting vine: Pierce's disease peril spurs research throughout state
The future of California's $33 billion wine industry might hang on an unlikely marriage of grape vines performed at the University of California, Davis.
Each spring, UC Davis grape breeders Alan Tenscher and Andrew Walker plant more than 2,000 exotic young vines in the hope that one or two will emerge with fully flavored grapes and a high degree of resistance to plant-killing Pierce's disease. Through conventional breeding of obscure varieties with popular wine vines like Cabernet, they are seeking a long-term answer to a disease that has vexed scientists and farmers for decades.
"Hopefully, we are going to be moving beyond just palatable (grapes) into the realm of good wine," said Tenscher, a former senior winemaker in Napa.
His work is part of a five-year, $166 million push to control Pierce's disease and the glassy-winged sharpshooter that carries it - an effort that stretches from Davis vineyards to a bug-breeding colony near Bakersfield.
The importance of the research was highlighted again this month when Solano County reported an outbreak of glassy-winged sharpshooters - the closest infestation yet to Napa and the heart of the state's wine industry. Solano officials found sharpshooters in a half-square-mile area near the Vacaville Premium Outlets.
Glassy-winged sharpshooters, native to Mexico and the southern United States, transmit lethal Pierce's disease much more rapidly than their California cousins. The bacterium that causes Pierce's disease clogs the circulatory system of plants, blocking the flow of water and nutrients.
"It's one of the largest challenges we face," said Kevin Hackett, national biological control program leader for the research arm of the U.S. Department of Agriculture. "We consider it a $33 billion threat."
Nationwide, Hackett's agency has 34 scientists working on Pierce's disease, sharpshooters and the crops they destroy.
The federal, state and university researchers are looking into virtually every aspect of the threat - from how sharpshooters reproduce and feed to which grapevine genes are responsible for disease resistance.
Outside Bakersfield, for instance, the California Department of Food and Agriculture has converted a watermelon seed plant into a breeding facility for stingerless wasps that feast on the eggs of glassy-winged sharpshooters. This month, the program dispatched its one-millionth wasp to subdue sharpshooters entrenched in Southern California.
"In their native habitat, sharpshooters are fairly well-controlled by predators and parasites like these (wasps)," said CDFA spokesman Jay Van Rein. "When they come over here on their own, they may not bring any of those natural enemies with them."
The wasp program is one of many with its roots in the 1999 Pierce's disease outbreak in Temecula, a Riverside County wine haven where the disease caused $20 million in damage and wiped out one-third of the vines.
Pierce's disease goes back more than 100 years in California. It destroyed 50,000 acres of wine grapes in Anaheim in the late 1800s, and the 1950s saw another major outbreak near Fresno. But the disease has a mysterious way of retreating between major outbreaks, lulling growers into thinking the worst is over.
It wasn't until the Temecula carnage that the state's growers got serious about research, assessing themselves up to $3 per $1,000 of grapes they sell and lobbying for federal and state funds.
Today, that money funds a major research symposium each winter, a wing of CDFA dedicated to the issue and a dozen UC Davis scientists with lab teams. All kinds of options have been developed to control the disease: insecticides, spray-on pest repellent and early-warning disease tests among them.
In the scientific community, the future lies in work like that being done by Walker and Tenscher at Davis - making grapevines that can withstand Pierce's disease.
"Everyone generally agrees that the resistance of the host (vine) ... probably in the long term will be the most effective, stable, reliable way to control and manage these diseases," said Ed Civerolo, director of USDA's Parlier station, where six senior scientists work full time on sharpshooter issues.
Walker, one of many who made Pierce's disease a priority when research money started to flow in the late 1990s, says there are three options:
* Breed vines that have natural disease resistance - typically little-known varieties from Mexico or Florida - with common wine grape varieties.
* Use emerging knowledge of vine genetics to isolate the genes responsible for disease resistance and insert them via genetic engineering into wine varieties.
* Genetically engineer anti-bacterial compounds into wine grape vines.
Each process is fraught with scientific uncertainty. No one knows what kind of impact spliced genes would have on any given variety or even exactly what sections of DNA must be inserted to achieve results.
Conventional breeding offers its own challenges, like how to get the berries to taste, feel and act exactly like the ones that consumers spend billions of dollars a year to enjoy. "Just because these things are spliced together doesn't mean they are going to work," said Walker.
Walker, a UC Davis graduate, splits his days among a lab in aging Wickson Hall, the sprawling test vineyards at the edge of campus, and his office.
There, he keeps a makeshift map of chromosomes in the grape plant and points to the address where he thinks the genes are located that create resistance to Pierce's disease.
Walker's patience and persistence are evident when he talks about the confounding realities of genetics. There is probably more than one gene responsible for disease resistance, he says, and no one knows how they interact. Walker remains undaunted by all the unknowns. "We are making good progress," he says.
The biggest question in his mind is not a technical one, but rather: Will the heritage-bound wine industry accept new hybrids or biotech varieties?
Right now, the answer is no. But Walker keeps it all in perspective, figuring that Pierce's disease will return one day with such ferocity that California will look for answers in his lab.
"My job," he said, "is to think 30 years in the future. Eventually, people are going to accept resistant varieties.
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