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Monday, September 08, 2008 |
Bt corn reduces fungi threat
Researchers from Iowa State University and USDA confirmed that Bt corn
hybrids can reduce infestation of toxic fungi. As Bt corn fends off corn
borer pests, it also reduces the levels of fusarium, a toxic fungi often
carried by the pests, say the researchers. The team says some Bt corn
hybrids are more effective than others. Their work will continue to
examine the effects different hybrids have on other mycotoxins.
Bt Corn Does Double Duty on Threats to Corn Crop
Iowa State University Office of Biotechnology
June 17, 1999
AMES, Iowa -- Researchers at Iowa State University and USDA have confirmed
that Bt corn reduces two threats to corn plants: corn borers and toxic
fungi. The genetically engineered corn hybrid is designed to ward off the
corn borer, and scientists recently discovered that it can lessen damage
from toxic fungi as well.
Bt corn contains genes from the bacterium Bacillus thuringiensis that
express proteins deadly to the corn borer, a common pest in cornfields.
When borers bore holes, as their name suggests, into the stalks and ears
of plants, they reduce crop quality and yield. Borers can also carry
Fusarium fungi into the plants, leading to ear and kernel rot. The fungi
can release mycotoxins, chemicals toxic to both animals and humans.
"Corn borer larvae cause physical injury to the plants, and that's where
Fusarium infections occur. Larvae can also carry Fusarium spores from the
leaf surface and transmit them to their feeding sites on the plants," said
Gary Munkvold, a plant pathology professor and researcher on the project.
Bt corn's protective design diminishes the likelihood of this chain
reaction. Cry protein genes from Bt bacteria serve as insecticides,
poisoning the hungry borers. Because the borers are killed off before they
can do much damage, they don't transmit as much fungi to corn stalks and
ears.
Munkvold, Richard Hellmich, a USDA-ARS researcher, and Larry Rice, a
USDA-APHIS researcher, discovered that some hybrids of Bt corn are more
effective than others in reducing levels of fungi because of variations in
the type of Cry protein and location in the plant. Nonetheless, Cry
proteins have a significant effect on the amount of corn borer feeding,
ear rot and toxins on the plant.
The scientists' findings offer good news for animal and human health. Some
species of Fusarium produce fumonisin, a dangerous toxin that can lead to
fatal diseases in horses and swine that ingest infected corn. The same
toxins are associated with esophageal cancer in humans.
"The difference in the amount of fumonisin in standard corn hybrids and Bt
corn in our study was significant. Fumonisins in the standard hybrids were
sometimes high enough to make corn kernels toxic to horses and humans.
When corn borers attack, fumonisin levels go up in standard hybrids, but
not in the Bt hybrids," Munkvold said. Related research by USDA
researchers in Illinois also supports that fumonisin levels are reduced in
Bt corn.
"Our results indicate that under some conditions, genetic engineering of
maize for insect resistance may enhance its safety for animal and human
consumption," he said.
The team is expanding their research to examine levels of other mycotoxins
on different Bt corn hybrids and the influence of Bt gene expression on
corn stalk rot.
A report of the team's findings was recently published in Plant Disease, a
publication of the American Phytopathological Society.
-30-
Contacts: Gary Munkvold, Plant Pathology, 515-294-6708
Richard Hellmich, ARS/Entomology, 515-294-4509
Danelle Baker-Miller, Office of Biotechnology, 515-294-7356)
Back to Bt Corn and Monarch Butterflies Page
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