Issue link: http://winesandvines.uberflip.com/i/562166
September 2015 WINES&VINES 73 WINE EAST WINE INDUSTRY NEWS C ollege Station, Texas—For decades, Pierce's disease (PD) prevented wineries from growing vinifera grapes across the southeastern United States—and was also found in Cali- fornia. Caused by the bacterium Xylella fastidiosa (Xf), PD is spread by a number of different vectors, including the glassy-winged sharp- shooter insect (GWSS). Rather than increasing the re- sistance level of grapevines to PD or zapping the vectors spreading it, Dr. Carlos Gonzalez, professor of plant bacteriology at Texas A&M, and his team of researchers developed a biocontrol system using bacteriophages to go after the bacterium itself. A bacterio- phage, or phage, is a virus that at- tacks bacteria, and in this case, Gonzalez' team isolated phages that target Xf. They used a "cock- tail" that included four different phages in order to make it effective against PD, even if the Xf became resistant to one of the phages. Historically, growers have used insecticides such as Admire to con- trol disease-spreading insect vec- tors such as GWSS. "It's critical to get other solutions," Dr. David N. Appel, professor of plant pathology and Texas A&M AgriLife extension specialist, told Wines & Vines. "The primary ingredient in these insec- ticides is Imidacloprid, which has been banned in Europe because of its effect on the bee population." Bacteriophages, however, offer a "green" alternative to pesticides because they are abundant in the environment and target specific bacteria. Drs. Stephen Ahern, Ma- yukh Das (above), Tushar Suvra Bhowmick and Ry Young worked with Gonzalez to isolate phages and determine their genetic diver- sity. The team has a phage bank with more than 100 phages, and from that they selected four viru- lent phages (known to the re- searchers as Sano, Salvo, Prado and Paz) based on their physical and genetic characteristics. Well- developed phage cocktails can act as a natural biocontrol, targeting a pathogenic bacterium without af- fecting humans, animals or plants or their associated microflora. The phage cocktail was then tested on grapevines grown in a greenhouse. Some vines were in- oculated with the cocktail before they were infected with the Xf bacterium, and others were in- fected first with Xf and then treated with the cocktail. Results showed that the phage cocktail worked to prevent disease devel- opment and stop the disease when it was already present. Field trials are currently being conducted in Texas, and additional trials are planned in California next year. "We'll need about two years of field data before we can apply for EPA approval as a biopesticide," Gonzalez added. The goal is to de- velop a sustainable phage treat- ment that is environmentally friendly and effective. —Linda Jones McKee Texas Researchers Develop Experimental Solution to PD Dr. Mayukh Das from Texas A&M AgriLife's Center for Phage Technology conducts Pierce's disease research. TEXAS A&M AGRILIFE RESEARCH