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Biotech Corn Hasn't Mixed With Maize in Mexico, Study Says

Posted on: Tuesday, 9 August 2005, 15:01 CDT

Aug. 9--Genetically modified corn hasn't mixed with native maize in southern Mexico, according to a study posted online this week by the Proceedings of the National Academy of Sciences.

The study contradicts results from four years ago, when scientists said modified corn genes had moved into the traditional crops, called maize in Mexico.

But scientists said gene flow -- which leads to the movement of traits from one plant to another -- is inevitable for both traditional and engineered plants because it happens during the constant, natural process of crossing.

"That's what plants do ...," said Roger Beachy, director of the Donald Danforth Plant Science Center in Creve Coeur. "They've been doing it for millions and millions of years."

The flow of an engineered gene isn't different from the movement of genes during the making of a hybrid flower or fruit. Missouri Botanical Garden Director Peter Raven said people need to stop "treating transgenes like viruses."

Instead, Raven and Beachy argue, the consequences of gene flow need to be examined individually, country by country, plant by plant, gene by gene.

"If there is a mixing, which there will surely be, the question is, 'What's the biological impact?'" Beachy said. "Is it a positive or a negative effect?"

Four years ago, two scientists at the University of California at Berkeley said in the journal Nature that genetic mixing in southern Mexico was "relatively common" and "maintained in the population from one generation to the next."

The study received attention because in 1998 Mexico imposed a freeze on planting of biotech crops. The mixing, if it happened, was because engineered corn had slipped across the border. The study later was discredited for its shoddy chemical analysis.

In the new study, Ohio State University ecologist Allison Snow looked for the unique markers of genetic modification in an analysis of more than 150,000 corn kernels harvested in 2003 and 2004 from Oaxaca, Mexico.

She concluded exactly the opposite of the Berkeley scientists: Genetic mixing was nonexistent. The maize was pure. And if transgenes existed at the time of the Berkeley study, they were eliminated in a few generations.

Barbara Schaal, a Washington University biologist, said the study raised doubts as to whether there was ever gene flow. But it will happen eventually -- for better or for worse, she said.

Often, genetic mixing results in positive traits farmers want. Sometimes the traits are neutral and are eliminated in a generation or two. Other times gene flow can be bad.

Undesirable gene flow has happened naturally and with genetically modified plants. In Canada, canola has been engineered to resist the Monsanto weed killer Roundup. The engineered canola has crossed with existing canola and caused problems for farmers who want to certify their canola as organic.

An international panel of scientists commissioned to study the issue of Mexican maize concluded in 2004 transgenes would cause no harm but said Mexico could regulate it however it wanted.

Schaal also said some plants exchange genes more readily than others. Rice plants, for instance, only breed with themselves. Moreover, rice grains often are polished before being exported, which sterilizes the seed.

That's why Schaal thinks rice is a good candidate for pharmaceutical applications. Ventria, a California-based pharmaceutical company, has proposed such an operation for Missouri. There would be very little chance of the pharmaceutical traits getting into the food supply, she said.

On the other hand, corn genes easily mix because corn plants like to breed with neighboring cousins, Snow said. Also, exported corn grains often are viable seeds.

Just as transgenes appear to be eliminated in Mexican maize, the Mexican government has taken action that likely will encourage more genetically modified corn to be planted. President Vicente Fox signed a law that ends the de facto freeze and encourages biotechnology through a process that will give special attention to preserving the biodiversity of maize.

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MON,

Source: St. Louis Post-Dispatch

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