Washington Post
March 25, 2002
By Marc Kaufman

The origins of modern corn can be traced to the remote valleys of Central America, where it was first cultivated 10,000 years ago from the wild teosinte plant. What is grown today in the vast cornfields of Iowa and on small local farms may have only limited genetic resemblance to those agricultural ancestors, but southern Mexico in particular remains the center of corn genetic diversity around the world.

That's why the international scientific battle now raging over the reported presence of genetic material from genetically engineered plants in Mexican corn is so bitter and emotional. The Mexican government banned the planting of modified corn in 1998 precisely because it didn't want its native stock to be mixed with the sometimes controversial creations of crop biotechnology. But new -- and hotly contested -- research suggests that the commingling has happened anyway.

The Mexican corn drama began last fall, after two researchers from the University of California at Berkeley prepared to report that they had found telltale sequences of genetically altered corn in the genome of corn from the hills of southern Mexico. The results were first published in a letter in the journal Nature, and then in a full article. They were decried by the Mexican government but widely disseminated by groups generally opposed to genetically engineered crops.

The two researchers wrote that they had conclusively found traces of the cauliflower mosaic virus -- widely used as a "promoter" to drive the activity of newly inserted genes -- as well as other samples of genetically modified DNA in ears of corn from two locations around Oaxaca.

"I had believed for some time that it was possible for transgenic DNA moving out into Mexican farmers' fields, and nobody seemed interested in monitoring that," said Ignacio Chapela, who conducted the study with David Quist. "We did the monitoring, we found the transgenes that were not supposed to be there, and then we got viciously attacked by people who didn't like our answers."

There indeed was an immediate response from scientists, especially those who support crop biotechnology, who attacked the researchers' conclusions and methodology. In particular, critics said the researchers relied on a testing method that is known to produce false positives for the presence of genetically modified DNA -- the commonly used polymerase chain reaction (PCR) method -- and that their research was not broad enough to support the conclusions they drew.

"Their work was mysticism masquerading as science," said Matthew Metz, a post-doctoral fellow in microbiology at the University of Washington. Metz, who was a graduate student in Chapela's department at Berkeley, is one of four who have submitted critical letters to Nature.

"There are a lot of political issues in the background here, but the primary concern for many of us is that science is being abused, that the scientific process is being taken advantage of for ideological reasons," Metz said.

The dispute quickly escalated, with charges made by both sides that central players had damaging conflicts of interest, and that scientists were essentially acting from political and commercial motives. Chapela said he was personally intimidated and threatened by fellow scientists and Mexican officials; critics said that at Berkeley, he had a track record of opposition to biotechnology that made his science highly suspect.

The charges and countercharges are difficult to disentangle, but the stakes are plainly high. As producers of genetically modified crops seek to sell their products around the world, opponents of the technology (who worry it could have as-yet undetected environmental and health consequences) are eager to find examples of biotechnology that have caused regulatory and financial disruptions.

The most prominent case involved StarLink corn, which had been approved in the United States only for use in animal feed but was found in hundreds of corn products from tacos to grits. But there are a growing list of others: Thousands of acres of genetically modified cotton have been found in India, although it was never approved for use there. A class action suit was filed recently by organic farmers in Canada, who said their canola crop was being tainted with genetically modified canola blowing in from neighboring fields. And now there is the possibility that the cradle of corn has been forever changed.

Some initial tests by the deeply worried Mexican government seemed to confirm the conclusions of the Nature article, but subsequent testing has raised new questions about the PCR process.

Timothy Reeves, executive director of the International Maize and Wheat Improvement Center in Mexico, an international nonprofit group that has collected a germ bank of corn species, said that none of its extensive testing has found genetic material from modified plants in Mexican corn. He also said that a recent set of tests by the Mexican government demonstrated how unreliable PCR testing can be. The government, he said, performed PCR testing on kernels of corn from the center's germ bank and found that many were tainted. But some of those kernels had been in storage for 20 or 30 years, Reeves said, and so could not have been affected by recently engineered varieties.

Nonetheless, Reeves also said the Nature article turned what his organization always knew was a theoretical threat into a real and pressing problem. He said it is quite possible that corn with some products of genetic engineering is growing now in Mexico, or will soon be growing there, despite its ban. That is just how corn, and people, behave. "The corn that people think of as native Mexican varieties have actually been evolving over centuries, and still are changing all the time," Reeves said. "It's a dynamic process, and new genetic material is being introduced through cross-pollination in every new crop."

The winds, however, may not have been responsible for the reported transgenic material in Oaxaca corn. Since the North American Free Trade Agreement (NAFTA) was signed, millions of tons of American and Canadian corn have flooded the Mexican market, and between 30 percent and 40 percent of that corn is grown from genetically engineered kernels. Although those seeds may not be planted under Mexican law, researchers theorize that farmers may well have planted them anyway - either to try their possible benefits or through ignorance.

The inevitability of the spread of engineered genes into some conventional Mexican corn raises what Reeves said is the key question in the debate that is just now beginning: Does it matter? Advocates of biotechnology say that it does not, that natural selection will ensure that only useful traits are kept and that others will simply disappear. Critics say the possibility of harm from those genes is too great to risk their indiscriminate and unplanned spread.

"We don't want to fall into the trap of saying [the possible presence of modified DNA in Mexican corn] is a disaster without real evidence," said Reeves. "But we also don't want to fall into the trap of saying it's no problem, either. This is a serious issue that has to be addressed with rigorous science."