Natural Cocktail Used to Prevent, Treat Disease of Wine Grapes

Jo-Carolyn Goode | 8/4/2015, 5:04 p.m.
It’s happy hour at a lab in College Station. The cocktail of choice, developed by scientists with Texas A&M AgriLife ...
Dr. Mayukh Das, with Texas A&M AgriLife’s Center for Phage Technology in College Station, works in a vineyard while doing Pierce’s disease research. (Photo courtesy of Texas A&M AgriLife Research)

COLLEGE STATION — It’s happy hour at a lab in College Station. The cocktail of choice, developed by scientists with Texas A&M AgriLife Research, is one that stops or prevents the deadly Pierce’s disease on wine grapes.

The discovery could turn a new leaf on the multimillion-dollar U.S. wine industry. Hear, hear.

The study, published in the academic journal PLOS-ONE, describes the use of four bacteriophages that were identified for their ability to attack the bacteria that causes the devastating disease in grapes and several other plants.

A bacteriophage, or phage, is a virus that attacks bacteria. Because they are abundant in the environment, scientists are trying to learn more about the different types and what specific bacteria each can attack. Scientists at AgriLife Research were able to isolate four phages that specifically target Xylella fastidiosa, the culprit in Pierce’s disease.

“The bacteria Xylella fastidiosa is native to the United States and causes disease in many plants including grapevines, oaks, peaches, almonds, coffee and citrus,” said Dr. Carlos Gonzalez, an AgriLife Research plant pathologist in College Station. “We have imported most of our grapevines from Europe, and so therefore the pathogen and the host – in this case the grapevine – did not co-evolve. That made the grapevines susceptible.”

The offending bacteria makes its way to plants via insects. In wine grapes, it’s the glassy-winged sharpshooter. When the insect feeds on a plant, the bacteria is transmitted inside the plant where it travels throughout the xylem vessels, infecting as it goes. The resulting condition, called Pierce’s disease, can cause a vineyard to die in anywhere from a few months to a few years after infection, according to Jim Kamas of Fredericksburg, Texas A&M AgriLife Extension Service horticulturist and outreach coordinator for the Texas Pierce’s Disease Research and Education Program.

“Instead of feeding on the leaves of a plant, the glassy-winged sharpshooter feeds on the cane of a grapevine and therefore spreads the bacterium much more efficiently,” Gonzalez explained.

The insect, about the size of a grain of rice, could feed its way into an estimated $24.6 billion of California wine sales in the U.S., according to the Wine Institute, and the Texas Wine and Grape Growers Association’ estimated $1.88 billion of economic value to the state.

Stopping the rampage with potential to make such an enormous dent in food and beverage supply heretofore relied on insecticides aimed at the carrier bugs.

However, the group of insecticides used have been shown to have adverse effects on beneficial insects such as honeybees and have already been banned in Europe, the scientists said. These concerns lead them to seek a biocontrol, or more natural way of preventing and treating diseases caused by Xylella fastidiosa, said Gonzalez, who also is part of the Center for Phage Technology in College Station where the research was done.

“Our approach basically was to directly address the bacterium that causes the disease rather than focus on the insect,” Gonzalez said of his colleagues at the center, Drs. Ry Young, Mayukh Das and Tushar Suvra Bhowmick. “The phage treatment offers an alternative to pesticides for the treatment of diseases caused by Xylella fastidiosa.”