The Guardian
April 19, 2002
By Paul Brown

The Mexican government has confirmed that despite its ban on genetically modified maize, there is massive contamination of crops in areas that act as the gene bank for one of the world's staple crops.

The announcement of the worst ever contamination of crops by GM varieties was made yesterday at the biodiversity convention meeting in the Hague.

It fuels the controversy stirred by the discovery of mutant strains of maize, which was originally reported in November in the journal Nature and then embarrassingly disowned by the journal earlier this month.

But speaking at the Hague, Jorge Soberon, a senior civil servant and the executive secretary of Mexico's national commission on biodiversity, said government tests had now shown the level of contamination was far worse than initially reported.

Mexico is the home of hundreds of varieties of maize which are allowed to crossbreed to produce the best crops for extreme conditions. To preserve this gene bank, the government banned planting of GM crops in 1998.

At first, Mexico rejected the claims of contamination which were published in Nature by Ignacio Chapela and David Quist, of the University of California at Berkeley.

But the government went on to take samples from sites in two states, Oaxaca and Puebla, said Ezequiel Ezcurra, the director of the Institute of Ecology at the Ministry of the Environment in Mexico. The states are the genetic home of maize.

A total of 1,876 seedlings was taken, and evidence of contamination was found at 95% of the sites. One field had 35% contamination of plants. Mr. Soberon confirmed this infiltration of supposedly pure strains was the worst recorded anywhere.

"There is no doubt about it," he said. "We found it in 8% of seeds kernel by kernel."

It appeared that maize imported into Mexico from the US for the production of tortillas may have been used as seed by farmers who were unaware that it contained grain derived from GM crops.

The worst contamination was found near main roads, along which maize is sold to villagers. In remote areas, contamination was down to between 1 and 2%.

The revealing factor was the presence of the cauliflower mosaic virus, which is used widely in GM crops to "switch on" insecticides which have been inserted into them.

Mr. Soberon said the GM developers Monsanto, Syngenta and Aventis all used the same technology.

The government could not find out which of the three varieties of GM maize was responsible for the contamination because the companies refused to disclose which protein they used in such a commercially sensitive project.

"I find that extremely difficult to accept," he said. "How can you monitor what is going on if they do not allow you the information to do it?"

The research is continuing and, after the dispute that followed the publication of the original paper, the Mexican government is having it carefully reviewed by peers before offering it for publication in a scientific journal.