GM Crop Genes Contaminate Mexican Corn

Feb. 23, 2009 -- Genes from genetically-engineered corn have been found in traditional crop strains in Mexico, according to a new study likely to reignite a bitter controversy over biotech maize.

The paper, by scientists from Mexico, the United States and the Netherlands, backs a 2001 probe that sparked a row over the safety of genetically-modified (GM) crops.

Green activists say GM crops are a potential hazard, arguing that their genes could spread to related plants through cross-pollination.

Their campaign has helped drive bans on GM crops in some countries, including Mexico itself, the ancestral home of maize, as corn is also called.

In the 2001 study, published in the prestigious British journal Nature, researchers reported finding transgenes in samples of corn taken from the Sierra Juarez region of Oaxaca.

But this study was blasted for technical inaccuracy and choice of samples. In an exceptional slap, Nature distanced itself from the paper, saying the evidence had not been strong enough to warrant publication.

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This damning verdict was underscored by a further study, carried out in 2005 by a different team, that was unable to replicate the results.

But new research now says the original study was right.

A team led by Elena Alvarez-Buylla of the National Autonomous University in Mexico City looked at nearly 2,000 samples from 100 fields in the region from 2001 and 2004, and found that around one percent of the samples had genes that had jumped from GM varieties.

"We confirmed that there was contamination in 2001 and also found contamination in 2004, which means that it either persisted in the local maize that we sampled or that it was reintroduced, which is less likely," Alvarez-Buylla said.

She said the difference between previous studies and her research lay in the samples chosen for gene sequencing and in the molecular technique for decrypting the DNA.

The investigators looked for two specific genes that had escaped from biotech corn, and found them in some fields but not in others.

Alvarez-Buylla said the evidence shed stark light on the failure of efforts to shield Mexico from unauthorized GM corn.

The country imposed a moratorium on the planting of transgenic maize in 1998 in order to protect genetic diversity. It is the home of about 60 traditional domesticated strains, also called landraces, as well as several wild strains.