The adult female European corn borer
moth lays fewer eggs on the B-96 corn
strain than on others. After scratching
and sniffing the surface of a B-96
leaf, she generally moves on
to a more desirable strain.
(K2634-8) |
An ugly duckling of the corn family
could hold secrets to save corn from its worst enemy—the European corn
borer.
"B-96 is scrawny. Its stalks are weak and its roots are undeveloped. Its
small ears have round kernels that resemble popcorn," says
ARS entomologist Bradley F. Binder. But
B-96, a corn strain originating from Argentina, possesses chemicals that other
corn lines covet—and that female European corn borers find less acceptable
for egg laying.
Working at the ARS Corn Insects and Crop Genetics Research Unit in Ames, Iowa,
Binder focuses on discovering new alternatives—other than applying
chemical or microbial insecticides to protect corn from corn borers.
"The struggle against the European corn borer has been tough for
farmers—especially those who grow crops with little or no chemical
pesticides," he says.
Yearly, the European corn borer causes losses of $350 million to the nation's
corn crop. Without preventive treatments, losses can exceed $1 billion.
Besides chemical controls, the only other practical alternative available today
is Bt corn—corn genetically modified to contain larvae-killing chemicals
produced by the bacterium Bacillus thuringiensis, or Bt.
Binder believes that he can combine the traits of Bt corn and B-96 corn to
provide a one-two punch against the borer. The resistance to egg laying from
B-96 corn and the larval control from Bt corn should keep the borer under
control.
Binder discovered the unknown trait of the B-96 strain—an inbred corn
line—in laboratory tests of corn strains preserved at the Ames Plant
Introduction Station.
Female corn borer moths have a sophisticated array of sensors to help find
suitable sites for depositing eggs. When a female lands on a corn leaf, she
fans her antennae to get a whiff of the plant's aroma. At the same time, her
feet scratch the leaf's surface. This scratching releases plant chemicals that
are thought to give insects more information about their chosen site.
"Unlike susceptible corn, B-96 has a chemical defense," he says.
After working with this inbred for 5 years, Binder believes one of the
chemicals is HMBOA, which belongs to a family of 20 chemicals. He has isolated
and synthesized this compound and developed a laboratory bioassay to test its
effectiveness.
Another chemical in this family, DIMBOA, protects young corn plants from
feeding borer larvae. Binder found that unlike most corn plants, B-96 plants
continue producing high levels of DIMBOA and HMBOA as they mature.
Currently, Binder is looking at lines related to B-96. Through field testing he
has found that corn borers lay relatively fewer eggs on these lines than on
susceptible lines.
"Apparently, female moths reject these plants in favor of susceptible
lines," he says. He is studying the underlying genetic basis for the
biosynthesis of these compounds in corn.
"Breeding this trait into corn could take 10 years," Binder cautions,
so he's not taking a short-term approach.
Meanwhile, he has found another corn line, called Illinois A (ILLA), that
"may offer even better resistance to egg laying," he says. "But
characterizing the chemical basis for ILLA resistance will require several more
years of research."— By Hank
Becker, Agricultural Research Service Information Staff.
This research is part of Plant, Microbial, and Insect Genetic Resources,
Genomics, and Genetic Improvement, an ARS National Program (#301) described on
the World Wide Web at http://www.nps.ars.usda.gov/programs/cppvs.htm.
Bradley F. Binder is at the
USDA-ARS Corn Insects and Crop
Genetics Research Unit, Genetics Laboratory, Room 110, Iowa State
University, Ames, IA 50011; phone (515) 294-6948, fax (515) 294-2265. |
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