February 23, 2009

Genes From GM Corn Found In Mexican Crops

Research from scientists in the United States, Mexico and the Netherlands has identified genes from genetically-engineered corn in conventional crop strains in Mexico.

The study is likely to reignite the bitter controversy over biotech maize.

The study supports a 2001 inquiry that sparked a dispute over the safety of genetically-modified (GM) crops, which environmentalists say are a potential hazard. 

Green campaigners argue that cross-pollination could spread genes of GM crops to related plants.  The initiatives against GM crops have helped achieve bans in some countries, including Mexico.

The 2001 study, which was published in the journal Nature, found transgenes in samples of corn obtained from the Sierra Juarez region of Oaxaca.   However, the study was criticized for technical inaccuracy and choice of samples.  And in an exceptional move, Nature even distanced itself from the paper, arguing that the evidence had not been strong enough to justify publication. 

This damning verdict was further underscored by a separate study conducted in 2005 by a different team, which was unable to replicate the results.

However, new research now seems to vindicate the original study.

Researchers led by Elena Alvarez-Buylla of the National Autonomous University in Mexico examined nearly 2,000 samples from 100 fields in the region from 2001 and 2004.  The team found that roughly one percent of the samples had genes that had transferred 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," said Alvarez-Buylla during an interview with AFP.

The difference between previous studies and the current research can be found in the samples chosen for gene sequencing, she said, and in the technique used in decrypting the DNA.

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

Alvarez-Buylla said the evidence clearly showed the failure of efforts to protect Mexico from unauthorized GM corn.

In 1998, Mexico imposed a moratorium on the planting of transgenic maize to protect genetic diversity.  The nation is home to roughly 60 traditional domesticated strains, called landraces, and many wild strains as well.

Alvarez-Buylla said she believed the transgenic seeds are likely entering Mexico from the United States, and getting combined with local seeds in trade among small farmers.

"It is very hard to avoid gene flow from transgenic maize to non-transgenic maize in Mexico, even though there has been a moratorium," she told AFP.

"It is really worrying that the government of Mexico has not been efficient enough in biosecurity monitoring," she added, accusing regulators of failing to set stringent molecular monitoring apart from data provided by biotech firms.

Alvarez-Buylla's team did not examine the impact of the escaped genes on the native corn, human health or the local environment, nor did it ascertain whether the foreign genes had passed on to progeny plants.

GM crops have had genes inserted into them to give them beneficial qualities, such as exuding toxins that kill off pests, being resistant to herbicides or enabling farmers to spray a field without killing the crops.  Producers of GM crops argue that there is no evidence of any threat to the environment or human health, a position in which a large number of scientists agree. 

However, many nations, particularly those in Europe, remain, suspicions and retain safeguard measures against GM corn.

The current research appears in the latest issue of Molecular Ecology, and has been endorsed by a lead author of the 2005 study.


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