November 29, 2001

2 min read

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GM Corn Contaminates Distant Native Plants

By Kate Wong

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Image: KANSAS STATE UNIVERSITY

In news that will surely fan the flames of the heated debate over genetically modified crops, scientists have found evidence that genes from GM plants can spread far and wide to native ones. According to a report published today in the journal Nature, wild corn from the remote mountains of Oaxaca, Mexico contains transgenic DNA. This, the researchers note, bolsters concerns that such unintentional contamination can threaten the genetic diversity of natural crops.

DNA analyses of the Oaxaca corn revealed several signs of gene transfer from transgenic plants, including a gene of Bacillus thuringiensis (Bt), a bacterium that produces a toxin lethal to common pests. The results came as a surprise to study co-author Ignacio Chapela of the University of California. "I repeated the tests at least three times to make sure I wasn¿t getting false-positives," he remarks. "It was initially hard to believe that corn in such a remote region would have tested positive."

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Indeed, exactly how the contamination occurred remains a mystery. Previously, some researchers have asserted that corn pollen is too heavy to be carried long distances by the wind. And Mexico has had a moratorium on the planting of GM corn since 1998. The closest a GM corn crop has ever come to the Oaxaca plants, as far as anyone knows, is 60 miles away. "It¿s not clear if the moratorium was poorly enforced, or the contamination occurred before the moratorium was enacted," Chapela comments. "Whatever the source, it¿s clear that genes are somehow moving from bioengineered corn to native corn."

The contamination is particularly troubling, Chapela says, because areas of crop origin and diversification like Oaxaca house "bank accounts" of genetic diversity¿the best insurance against disease, pests and changing climates. And with regard to global food security he notes, "we can¿t afford to lose that resource."

Kate Wong is an award-winning science writer and senior editor for features at Scientific American, where she has focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

More by Kate Wong

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