Scientists Probe "Fly Spit" for Clues to
Serious Wheat Pest
By Erin Peabody
January 8, 2007
The Hessian fly, the No. 1 global
pest of wheat, is not your ordinary insect. Its fiercest weaponcapable of
making wheat plants droop, topple over and even commit cell suicideis its
Based on findings by scientists with the Agricultural Research Service (ARS) in Manhattan, Kan., the fly appears to
put a lot of genetic stock in executing this unusual offensive. The ARS team
has identified at least 2,000 genes that play some role in churning out the
toxic salivary brew that the fly injects into wheat plants when taking a bite.
Led by entomologist
Chen, the researchers are zeroing in on these genes, in hopes of
pinpointing those that make the destructive Hessian fly such an elusive pest.
For thousands of years, wheat plants and Hessian flies have been squaring
off, with the fly trying to get access to its favorite food, as the wheat
plants guard themselves from attack. For every one of wheat's resistance genes,
there's a corresponding "avirulence" gene in the fly.
Even modern breeding efforts can't fully bolster wheat plants. At least four
of the most recent resistance genes introduced into wheat plants no longer
ensure an effective level of protection because of the fly's highly adaptive
Chen and his team, who work at the Grain Marketing and Production Research
in Manhattan, have identified 97 "superfamilies" of genes in the fly
that encode for toxic salivary proteins. This appears to be a hefty genetic
investment, given the fly's minute genome, considered one of the smallest in
the insect world.
The GMPRC researchers are also making progress in efforts to prop up
fly-weary wheat plants. They've mapped several resistance genes in wheat,
including the H9 and H13 gene clusters. These findings are helping breeders
conduct marker-assisted selection, a method for "stacking" multiple
protective genes into a single plant.
more on ARS's Hessian fly studies, see the latest issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.