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First, it was taco shells. Now native corn grown in remote mountains of Mexico has been found contaminated by foreign DNA introduced through biotechnology. First, it was taco shells. Now native corn grown in remote mountains of Mexico has been found contaminated by foreign DNA introduced through biotechnology.

Researchers at the University of California, Berkeley, who made the discovery in rural Oaxaca said the spread of engineered DNA, or transgenes, shows that the technology is out of hand.

"This perception of (genetically modified) crops as under control, and 'we really know what we're doing' . . . I think is really false, and this proves it, " said Ignacio Chapela, an assistant professor of microbial ecology at Berkeley. "If we want it, we should know we do not have it under control. "

How the foreign genetic material wound up in the corn is a mystery. Mexico has banned genetically-altered plants since 1998, although it allows transgenic corn imports for food.

The presence of foreign genes didn't change the corn in any noticeable way, but Chapela and David Quist, the graduate student who made the discovery, say they fear the situation could undermine the crop's genetic diversity in the long run. Their findings are published today in the journal Nature.

Plant biotechnology advocates and skeptics alike compared the research in Mexico to the revelation last year that a genetically altered corn variety approved only for animal feed was present in taco shells in the United States.

its discovery led to the recall of more than 300 food products from grocery store shelves. The corn variety, called StarLink, is engineered with a protein that's potentially allergenic to people.

The StarLink debacle demonstrated the extent to which foreign genes had spread, making the discovery in Mexico not so surprising, said Mark Lipson, member of a U. S. Department of Agriculture advisory committee on biotechnology.

"This confirms that virtually all the sources of genetic material are contaminated, and it's going to take a lot of effort to mitigate that, " said Lipson, who is policy program director at the Organic Farming Research Foundation in Santa Cruz. "There's probably no hope of completely ever saying, 'Yeah, there's zero. ' "

That conclusion has major implications for organic growers and sellers , who often market their products as "GMO free" -- using the acronym for genetically-modified organisms.

Lipson suggested that the issue could wind up as a [] legal fight.

"If, in fact, the degree of purity is required either legally or in the marketplace by the consumer, and you . . . can't ever have organic corn that is truly free of transgenics, who's going to bear the cost of that?" he asked. "Whose liability is that?"

Biotechnology proponents said the presence of foreign genetic material in the Mexican corn isn't by itself evidence of damage to the native crop.

"The concern about the plants overwhelming the native plants and driving out diversity has not been demonstrated yet, " said Kent Bradford, director of the Seed Biotechnology Center at the University of California, Davis.

In fact, commercial hybrid strains of corn probably have been sharing genes with native corns for years, Bradford said, and the native varieties apparently have survived well.

Jose Luis Solleiro, director of AgroBIO Mexico, A. C. , an industry trade group, made the same point in a letter circulated among people involved with biotechnology in the United States.

"There is no reason to believe that the presence of one or two transgenes would alter the course of natural selection, " Solleiro wrote.

Chapela, scientific director of a biological laboratory in Oaxaca, is not so sure. He calls transgenes "sticky, jumpy DNA" because people have managed to take them from one organism and put them in another. He fears that biotech plants are by nature more apt to share their genes than conventionally-bred plants.

Quist and Chapela said they are particularly concerned about the transgenes in native Mexican corn, because the region is recognized as an international center of genetic diversity for corn.

Quist made the DNA discovery while in Oaxaca planning a workshop to teach community members DNA analysis techniques. His plan was to show students how to find transgenes by comparing DNA of corn grown in the United States with local corn.

During a test run of the experiment before the workshop, Quist found that the local corn tested positive for foreign DNA.

Not sure whether he had an accurate result, Quist returned to Berkeley, where he ran the test again and again. He found that the foreign genetic material in most abundance came from cauliflower mosaic virus, which is used as a "switch" to turn on a gene. He also found an "off" switch from a bacteria, as well as a lesser amount of a bacterial gene that produces Bacillus thuringiensis, a type of pesticide.

Chapela said that although pollen from biotech varieties of corn may have entered the country on migrating insects or birds, transgenic corn probably was grown experimentally in Mexico before the 1998 ban. And then there is the imported food corn.

"People will admit to it: 'From time to time, I take the seed and I plant it just to try it out, ' " Chapela said. "The ban on planting is probably forgotten as soon as the corn enters the country. "

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News Service: Knight Ridder/Tribune

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