| Transgenic control of insect pests in maize reduces mycotoxin concentrations in grain | |
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Gary P. Munkvold, and R.L.
Hellmich Iowa State University Depts. of Plant Pathology and Entomology and USDA-ARS |
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The safety of food and feed products for consumption should be the primary
consideration in regard to regulation of agricultural and food production
industries. In terms of human food safety, foodborne microorganisms pose
the greatest threat, followed by mycotoxins produced by fungi in food products.
For the safety of livestock feeds, mycotoxins are recognized as the greatest
hazard. Mycotoxin-producing fungi include species of Aspergillus,
Fusarium, Penicillium, and others. Maize kernels grown throughout
the world are commonly infected by mycotoxin-producing fungi in the genus
Fusarium. Worldwide, the most common Fusarium mycotoxins in
maize are the fumonisins. This group of toxins can cause fatal diseases in
livestock and are carcinogenic. Conventional breeding methods have not been
successful in developing maize hybrids with high levels of resistance to
these fungi because of the lack of major resistance genes in maize. Infection
of maize by Fusarium species is greatly influenced by insect pests
such as the European corn borer. Insect larvae carry spores of the fungi
to the maize kernels and deposit them there. Furthermore, injuries to the
kernel tissue caused by insects are very vulnerable sites for fungal infection.
Therefore, there is a correlation between insect damage and fumonisin
concentrations in maize kernels. We therefore investigated the potential
for reducing fumonisin concentrations in maize kernels through insect control.
Highly effective insect resistance offered by transgenic Bt hybrids expressing
CryIA(b) or Cry9C in kernel tissue successfully prevented the accumulation
of significant fumonsin concentrations. Near-isogenic, conventional hybrids
often had fumonisin concentrations 10 times higher than those in the kernels
of these Bt hybrids. Partial insect control by synthetic insecticides, foliar
applications of Bacillus thuringiensis, or Bt hybrids lacking kernel
expression of Cry proteins, resulted in some less dramatic reductions in
fumonisin concentrations. Similar results have been reported from other states
in the U.S. and from Italy. These results indicate that the safety of maize
grain for consumption by humans and livestock can be enhanced through the
use of transgenic insect control. Bt hybrids are currently the most effective
management tool available for reducing fumonisin concentrations in maize
grain. |
Ear samples from a 1997 field trial. |
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A summary of this work is available at :
http://www.scisoc.org/feature/BtCorn/Top.html Related information can be found at: http://www.scisoc.org/feature/BtCorn/0422-04F.pdf |