MADISON -- Working with teosinte, a wild cousin of maize, a University of Wisconsin-Madison scientist has found a molecular barrier that, bred into modern hybrid corn, is capable of completely locking out foreign genes, including those from genetically modified corn.
The discovery is important because it means farmers will have access to a technology that can ensure the genetic integrity of their corn crop, making it easier to export to countries wary of recombinant DNA technology and providing a built-in buffer for potential environmental problems such as the threat to monarch butterflies from corn engineered to make its own biological insecticides.
"Governing the flow of genes between populations is what's at stake," says Jerry L. Kermicle, the UW-Madison professor of genetics who discovered teosinte's genetic barrier.
Corn varieties of all kinds -- from organic to genetically engineered -- are prolific traffickers in genes. Cross-fertilization between strains occurs as gene-laden pollen is carried by bees or blown with the wind from one field to another. The resulting contamination, especially from genetically modified corn, can ruin organic crops or make traditional hybrid corn worthless for export to countries where consumers are wary of the new technology.
The new discovery, however, could permit American farmers to recapture those profitable markets in Europe and Asia by ensuring that organic or traditional hybrid corn is uncontaminated by genes from genetically modified crops.
Moreover, the new technology can be used by farmers to plant buffers around fields of corn genetically modified to make their own insecticides and thereby limiting a highly-publicized threat to non-target species such as monarch butterflies.
For thousands of years, teosinte has co-existed as a weed with the maize cultivated in Mexican fields. Like corn, teosinte is a grass and its genetic makeup is so similar to that of cultivated maize that scientists suspect the genetic differences between the two plants may be confined to a mere handful of genes. Teosinte, in fact, is corn's likely ancestor.
Despite this genetic affinity -- and the ease with which cultivated corn plants exchanges genes through cross pollination -- the teosinte strains that grow as weeds within Mexican corn fields only rarely acquire genes from cultivated corn.
The reason, according to Kermicle, is that teosinte has a built-in barrier, governed by a single gene cluster, that keeps foreign maize genes out, enabling the plant to maintain its own unique genetic identity in an environment thick with gene-laden pollen. The ability to build a genetic barrier into hybrid corn is a significant technological advance, one that would permit farmers to assure buyers that the corn from their fields has not been contaminated by genes from neighboring fields. The technology, according to Steve Gerrish, an agronomist and licensing associate with the Wisconsin Alumni Research Foundation, would have instant appeal to organic farmers and farmers whose corn or corn products might be marketed to countries that now bar imports of genetically modified grain.
"This technology can potentially solve the problem of contamination of regular hybrid corn and organic hybrid corn by any genetically modified organism (GMO) during the growing season," says Gerrish. "This technology could also allow a farmer to grow both types of maize crops and maintain a market segregated product."
Today, about 22.6 percent of the corn grown in the United States is exported to other countries, 8 percent is used for sweeteners, 2.6 percent for starch, 5 percent is used in the manufacture of alcohol, and 1.2 percent is used in products for human consumption. A little more than 50 percent of the U.S. corn crop is used for animal feed. But even in the animal feed market, according to Gerrish, there is a growing interest in corn certified as a non-genetically modified organism, especially for organic livestock production which requires grain produced by plants that are not genetically engineered.
The reluctance of key foreign trading partners, including the European Union, Australia, Japan and other nations, to import genetically modified products has become a significant problem for American farmers as they compete in the international marketplace. In the United States, genetically modified crops, including corn and soybeans, are now planted on millions of acres of farmland.
Using traditional breeding methods, the genetic barrier is being transferred to hybrid corn and testing quantities of seed should be available through seed companies in 2002, Gerrish says. Commercial quantities for planting by farmers are possible by the year 2003, he says.
The new gene-barrier technology has been patented by WARF, a private, not-for-profit corporation that manages intellectual property in the interest of UW-Madison. It will be licensed non-exclusively for domestic and international use. Licensing terms will include a provision that GMO technology be kept out of maize varieties with the teosinte barrier.
In addition to its commercial potential, Kermicle's discovery may also provide new scientific insight into the genetic barriers that prevent other plant and animal species from acquiring foreign genes.
It may be that similar genetic barriers exist in nature for other commercially important plants, Gerrish says, and Kermicle's discovery is certain to inspire quests for those plants and their respective barrier genes.
Materials provided by University Of Wisconsin-Madison. Note: Content may be edited for style and length.
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