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DNA from genetically modified maize has been found in native strains of the crop in a relatively remote region of Mexico, heightening concern about the potential effects of transgenic crops on plant diversity.

David Quist and Ignacio Chapela from the University of California compared wild maize strains growing on mountains in the Oaxaca region of Mexico with transgenic varieties and with samples known to be uncontaminated. They found that some of the wild varieties contained DNA from transgenic strains.

It remains unclear, however, how the DNA from the transgenic crops got into the wild plants. Growing transgenic maize in Mexico has been banned since 1998, although importing genetically modified foods into Mexico is allowed.

The researchers suggest that the DNA may have entered the genome of wild strains before 1998. Alternatively it could have happened when genetically modified grain imported as an animal food product was planted near traditional crops.

The results of the study — which appears in the 29 November issue of Nature — were first revealed in September by a Mexican official, when describing the results of studies that had been carried out in a Mexican research laboratory to check Chapela’s initial findings.

The Mexican environment ministry has also released partial results of its own study, which showed that transgenic corn was found in 15 of 22 areas tested in Oaxaca and Puebla.

The findings have led to strong protests from environmental groups, who argue that contamination by transgenic crops is a potential threat to plant biodiversity. "Contamination from genetically engineered corn to local corn varieties in Mexico could cause their extinction,” said Dr. Doreen Stabinsky, science advisor to Greenpeace. “If this diversity is lost, future food security is at risk."

The International Maize and Wheat Improvement Centre (CIMMYT), which is based in Mexico and carries out research on transgenic crops, describes the findings as a “serious development”. However it has stressed that its own research on genetically modified maize is conducted in the laboratory or in greenhouses.

Link to full text in Nature 414, 541 (2001)

© SciDev.Net 2001

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