Damm. Now the food's not even safe

NOW it's official: genes from genetically modified corn have escaped into wild varieties in rural Mexico. A new study resolves a long-running controversy over the spread of GM genes and suggests that detecting such escapes may be tougher than previously thought.

In 2001, when biologists David Quist and Ignacio Chapela reported finding transgenes from GM corn in traditional varieties (external - login to view) in Oaxaca, Mexico, they faced a barrage of criticism over their techniques. Nature, which had published the research, eventually disowned their paper (external - login to view), while a second study by different researchers failed to back up their findings.

But now, Elena Alvarez-Buylla (external - login to view) of the National Autonomous University in Mexico City and her team have backed Quist and Chapela's claim. They found transgenes in about 1 per cent of nearly 2000 samples they took from the region (Molecular Ecology, vol 18, p 750).

"They are out there, but it's hit-and-miss," says Paul Gepts of the University of California, Davis, a co-author of the new study. The escaped transgenes are common in a few fields and absent in others, he says, so gene-monitoring efforts must sample as broadly as possible.

What's more, not every detection method - or laboratory - identified every sample containing transgenes. Monitors should use many methods to avoid false negatives, says Gepts.