Genome of Grapevine Culprit
Revealed By Marcia Wood
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
St. John, associate deputy administrator at the agency's Beltsville, Md.,
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
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.