GMOs and corn mycotoxins
There are several caveats and complicating factors in this line of research, as follows:
- Bt corn isn’t a “magic bullet”, eliminating all mycotoxin contamination. Indeed, sometimes reductions in mycotoxin contamination do not occur. This is true for both fumonisins and for aflatoxins. However, reductions of fumonisins and aflatoxins have been documented commonly in field studies, especially under conditions moderately to highly favorable for ear rot and mycotoxin contamination. Such reductions occur commonly enough—with no known “downsides” relating to consumption of the grain—that the appropriate use of Bt corn is considered to be beneficial both for food safety as well as for animal health.
- The Bt toxin must be expressed in the corn kernel in order to reduce insect injury and, ultimately, mycotoxin levels. In some Bt corn hybrids, the Bt toxin is not expressed in the kernel. Such hybrids have no protection against wounds created by insect feeding, and therefore fumonisin contamination is not reduced in these hybrids.
- While the Bt trait is important in reducing mycotoxin contamination, the magnitude of mycotoxin reduction can depend on the genetic background of the corn hybrid. In other words, if you compare two hybrids that have the same Bt trait, one may have less fumonisin than the other, simply because of its genetic background.
- The effectiveness of the Bt trait in reducing mycotoxin contamination depends on the insect pest present. For example, Bt corn is often effective at reducing feeding damage from the European corn borer, but not the corn earworm. Consequently, reductions in fumonisin contamination may occur if the European corn borer is the principal pest in a field, but not if the corn earworm is predominant.
Corn hybrids that express the Bt trait in kernels sometimes exhibit reduced kernel contamination from fumonisins and aflatoxins. This is thought to be due to reduced insect feeding on the kernels.
The Bt trait is not a “silver bullet”, eliminating all mycotoxin risk. However, reductions occur commonly enough, with no known “downside”, that the Bt trait is thought to contribute to food safety and livestock health in both developed and developing countries. While it is well-documented that the Bt trait can reduce mycotoxin contamination, it is best used wisely, and only in fields with a moderate to high risk of damage from the target insect pests.
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