Genome of Grapevine Culprit Revealed

By unlocking secrets to the genetic makeup of the microbe that causes Pierce's disease of grapes, scientists may be better able to fend off this pathogen in the future. USDA's Agricultural Research Service helped coordinate funding of a binational effort to determine the structure, or sequence, of every gene in the microbe, according to Judith St. John, associate deputy administrator at the agency's Beltsville, Md., headquarters.

Known as Xylella fastidiosa, the bacterium is carried to plants by a nearly inch-long insect known as the glassy winged sharpshooter. The microbe is introduced into grapevines when the sharpshooter punctures stems to feed on sap. Inside the plant, the bacteria multiply, blocking the flow of water and nutrients. Severely infected vines die. Neither the sharpshooter nor the microbe harms humans.

Brazilian researchers--aided by funds from ARS, the American Vineyard Foundation, California Department of Food and Agriculture, and the São Paulo State Research Foundation in Brazil--have now sequenced the genome of the Xylella fastidiosa strain responsible for Pierce's disease.

Their work provides an important foundation for the next task, which is to determine the functions of individual genes, according to St. John. Using computers, researchers can compare the X. fastidiosa gene sequences to those from known genomes of other organisms. Because genes with the same sequence usually have the same function, the matching-up process shortens the amount of time it would otherwise take to discover a gene's function.

Scientists anticipate that knowing more about the specific genes that enable X. fastidiosa to replicate inside grapevines, for example, may lead to new, environmentally friendly strategies to protect tomorrow's vineyards from this enemy.

In addition to supporting the genome sequencing work of the Brazilian scientists, ARS is funding other Pierce's disease research, including experiments by agency scientists to test repellents and insecticides. ARS is the USDA's chief research agency.

Pierce's disease poses a major threat to California's $2.7 billion wine, table and raisin grape industry, according to St. John. Currently, there is no cure for the disease.