Newsweek
January 28, 2002
By Alan Zarembo

A researcher's discovery embarrasses the government, strikes fear in farmers and reignites a scientific debate

Olga Toro Maldonado was short on corn seed and slightly curious. In the spring of 1998, alongside the corn she had always raised on her hillside plot, she planted 60 kernels purchased from the government store. "The corn looked good," she recalls, so the next year she planted a cross between the two species. The harvest was smaller than the year before--one ear per stalk rather than the usual two--but the corn was tasty enough. She ground it into flour for tortillas and fed the kernels to her chickens.

A few scientists stopped by in fall 2000 and took away samples from her most recent harvest. They returned a week later with some disturbing news. Toro's corn contained transgenes--genes from bacteria and other organisms artificially introduced into the corn to make it resistant to herbicides or insects. Toro, 40, heard the word "contamination" and began worrying about her six children, her chickens and whether the pollen from her corn had spread. "I feel guilty," she says. "But another woman told me she planted it, too. I'm not the only ignorant one. We don't know the damage we can do." The head scientist was Ignacio Chapela, a 42-year-old Mexican and a microbial ecologist at the University of California, Berkeley. His team collected corn from the mountains of Oaxaca, in southern Mexico, and found that several samples contained transgenes. The finding was startling because the Mexican government bans the planting of genetically modified (GM) corn. And the agriculture industry has long contended that contamination from GM crops was extremely unlikely. "I was dumbfounded,"

Chapela says. "I knew it was a difficult political fray we were getting ourselves into."There is no evidence that GM corn is dangerous for human consumption. Chapela and his allies are concerned instead that GM corn might pose a threat to corn's biodiversity. Mexico, where corn was first domesticated 10,000 years ago, is what scientists call the crop's "center of genetic diversity"--a kind of repository of traditional varieties. GM corn, with its engineered advantages, could theoretically overwhelm these indigenous types. That would leave breeders without a source of pristine seed if a plague struck corn crops elsewhere. "World food security depends on the availability of this diversity. Having it contaminated is something humanity should worry about," says Chapela.

Mexico, the corn-consuming capital of the world, has been cautious about corn. Congress banned GM corn crops in 1998 even while allowing GM cotton and tomatoes. The current administration has been considering loosening the ban in an effort to improve agriculture and attract investment. A combination of decades of bad agricultural policy and falling trade barriers with the United States has turned Mexico into an importer of its staple food: 6 million tons of corn a year come from the United States. A panel of scientific advisers recently recommended opening northwest Mexico, which has none of the traditional strains of corn, to transgenic corn crops. "Mexico as a country cannot exclude itself from biotechnology," says Victor Manuel Villalobos, the under secretary of Agriculture. "It is not an intelligent position to say that because there are risks we won't touch it."

Chapela's revelation that GM corn is already growing in the hills of Oaxaca is an embarrassment to the Mexican government, to say the least. After Chapela's paper appeared in the scientific journal Nature in November, a Greenpeace activist declared the contamination "a worse attack on our culture than if they had torn down the cathedral of Oaxaca and built a McDonald's over it." The group began urging indigenous groups in Oaxaca to sue the federal government. Eighty scientists from 12 countries demanded the government take steps to contain the damage.

The government's own tests found transgenes in Oaxaca and neighboring Puebla, as had Chapela, but Villalobos maintains that more detailed studies now underway may very well refute Chapela's findings. Meanwhile, he warned Chapela in a letter dated Nov. 28 that the federal government "will take measures... to redress the great damages, as much to agriculture as to the economy in general, that... your publication might have caused." The economic damage stems from a bizarre irony: even though Mexico bans GM corn crops on its soil, a third of its imported U.S. corn is transgenic. If public sentiment turns against GM corn, officials argue that having to import only non-GM corn would raise prices for consumers.

U.S. corn is the most likely source of the genetic contamination. It arrives in sacks mixed with unmodified varieties and often ends up at government stores, where it is sold as food for the poor and their animals. U.S. biotech firms instruct farmers to keep buffer zones around GM corn to prevent foreign genes from spreading, but the stores of Oaxaca, where peasant farmers shop, have no warning signs at all. Toro's corn grows near a hilltop, above the pueblo of Calpulalpan, with pine-green mountains in the distance. As she points out which corn stalks are crosses and which are pure, a strong wind sweeps by--strong enough, perhaps, to spread pollen to nearby plots. Indeed, Chapela found transgenes on farms where store-bought corn was never planted. As word of Chapela's discovery trickled through Oaxaca, villagers were fearful that the government was going to burn their fields or prosecute farmers. At the government store in Calpulalpan, the 59-year-old clerk, Elfego Martinez Perez, claims the corn "can cause a disease called cancer." (That hasn't kept him from selling it or eating it himself.)

Chapela's detractors, including many scientists, accuse him of exaggerating the dangers. The term "native corn" is a misnomer, they say, because farmers have been modifying the genetic makeup of corn through selective breeding for thousands of years. "We' ve got a lot of utopian idealists worried about contamination of the old corn varieties with the new. This is completely idiotic, the way it has been presented," says Norman Bourlag, a Nobel laureate and founder of the International Wheat and Maize Improvement Center near Mexico City. Since none of the genes found in the GM corn were active, the corn didn't exhibit the traits engineered into it. Even if it did, some critics argue, the GM corn wouldn't necessarily have a selective advantage because it was engineered to grow well in the United States, not Mexico. "Just the presence of one new gene is not going to destroy maize in Mexico," says David Hoisington, head of the Applied Biotechnology Center at the Wheat and Maize center. "It's not a threat to biodiversity. It's just one gene among 50,000 to 60,000 genes." Officials at Monsanto, which holds a patent on at least one of the genes Chapela found, makes the same argument.

Regardless of which side in the gene wars is correct, one thing is clear: now that transgenic corn has been let loose in Mexico, stopping its spread is next to impossible. Bans on the imports of GM corn, as Greenpeace has called for, would accomplish nothing. And what if all the GM corn in Oaxaca magically disappeared? Some of the thousands of Mexican migrant workers who return each year from the United States no doubt carry kernels they reckon might grow well back on the hillside back home.