Threat to Grapevines and Gardens Now Easier to
Pinpoint By Erin
Peabody June 19, 2007
It used to be that tracking the bacterium Xylella
fastidiosaone of the most serious threats to the California wine
industrywas as challenging as teasing out the fine, commingling aromas of
a complex Bordeaux.
Now, scientists with the Agricultural Research Service (ARS) in Beltsville, Md., have developed a
method for quickly confirming whether an insect or plant harbors the
destructive, disease-causing bacterium.
X. fastidiosa is best known for causing Pierce's disease in
grapes, having ravaged California vineyards throughout the 1990s. But this
menacing microbe, transmitted by various piercing insects, also attacks
almonds, peaches and plums, as well as landscape trees as economically
important as elms, oaks and sycamores.
Huang, a plant pathologist in the
Floral and Nursery Plants Research Unit, a part of the
National Arboretum operated by ARS in Washington, D.C., developed the new
method for quickly finding out if an insect carries X. fastidiosa. She's
reduced the sticky business of extracting and analyzing bacterial DNA from
inside an insect to two simple steps, which can be completed in under a day.
Little is generally known about the particular X. fastidiosa
strains impacting landscape trees and how they differ from strains plaguing
vineyards and other crops. Especially vexing is not knowing whether the
isolates responsible for causing Pierce's disease in grapes can affect
landscape plantsand vice versa.
The new method should help fill in such gaps in knowledge about
transmission of different isolates of the Xylella bacterium.
Huang's test relies on two parts: a commercially available
DNA-extraction kit and a DNA-amplification protocol that uses
primersshort pieces of DNA specific to the bacterium's genetic
codeto serve as proof of its presence.
The new method is more powerful than the current
Xylella-detecting standby, which uses technology known as ELISA, for
"enzyme-linked immunosorbent assay." ELISA can't recognize low levels of the
bacterium, which has likely left many potential Xylella-transmitting
insects to go undetected.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.