Mexicans angry over modified corn's spread into local varieties

MEXICO CITY -- In a cautionary tale about the difficulty of controlling genetically modified plants, corn researchers in Mexico went ever higher into remote mountain villages looking for natural varieties of the 4,000-year-old crop.

Time after time, they couldn't find them.

Samples revealed that just a few years of unlabeled U.S. imports had transferred modified genes to local corn in the state of Oaxaca -- even though planting genetically modified crops is banned in this country, the birthplace of corn.

The discovery, confirmed in the science magazine Nature, caused outrage among Mexicans, whose ancestors believed the gods created mankind from an ear of corn.

"It's a worse attack on our culture than if they had torn down the cathedral of Oaxaca and built a McDonald's over it," said Hector Magallone, an activist with environmental group Greenpeace.

There is no evidence that genetically modified grains harm those who eat them.

A genetic warehouse

But some scientists worry that genetically modified strains could displace or contaminate Mexico's genetic warehouse of over 60 corn varieties -- a wealth that enriches staple crops worldwide and includes wild varieties that have yet to be cataloged.

The accidental spread of laboratory-inserted genes, scientists fear, could allow aggressive plants to crowd out other varieties, reducing biological diversity.

Diversity is prized as a hedge against disease, pests and climate change. While some plant strains may be vulnerable to one disease, others may have natural immunity that enables them to survive.

But supporters of genetic modification say such crops may actually benefit the environment by allowing farmers to use less pesticide or soil tilling, cutting down on erosion.

Mexico is a net importer of corn -- about 6.2 million tons annually, almost all from the United States. Perhaps one-fourth of it is genetically modified. Corn, which is Mexico's staple crop, is imported mostly for human and animal consumption -- not as seed.

Yet several modified strains were found, including one that makes the plant produce a toxin to ward off corn borers.

It is unclear how far the genetically modified crops have spread. A study by the Mexican Environment Ministry earlier this year found them in 15 locations in Oaxaca, but in low concentrations of 3 percent to 10 percent of plants in most fields.

Accidental discovery

Researchers from Oaxaca's Uzachi agricultural research center weren't looking for genetically modified corn when they went to the Zapotec Indian village of Calpulalpan in late November 2000.

They went to the area high in the Sierra Norte mountains to find pure, locally occurring varieties that would serve as a 'control sample' for a project to produce natural, organic corn.

But researcher Francisco Chapela recalls that, when they analyzed the sample, it contained a genetic marker used in engineered plants.

"At first we thought our equipment was malfunctioning," Chapela said. "Then, we thought, 'OK, maybe this field had some problems, we'll go to another one farther back in the mountains.'"