Associated Press
April 4, 2002
By Andrew Bridges

A prestigious scientific journal is backing off a study concluding DNA from genetically modified corn contaminated native maize in Mexico, amid an unusually public and bitter exchange between its authors and their critics over "bad science" and questions of incompetence.

In late November, the British journal Nature published a study by University of California, Berkeley scientists claiming genes from laboratory-altered strains of corn had found their way into indigenous maize in rural Oaxaca.

The finding further clouded the contentious debate over genetically modified crops and raised new fears among activists of threats to the diversity of corn in the very region where the plant was first domesticated millennia ago.

Mexico banned the planting of transgenic corn in 1998 to protect the genetic integrity of its indigenous maize.

In a terse statement published Thursday on the journal's Web site, editor Philip Campbell said Nature "has concluded that the evidence available is not sufficient to justify the publication of the original paper."

Rather than retract the study, Nature printed two criticisms of the work, as well as a rebuttal from the authors. Their reply includes new data resulting from further scientific work. The journal's editors, in an unusual move, requested the Berkeley scientists undertake the work to bolster their contention or face a demand for a retraction.

The journal stopped short of declaring the research flawed. Instead, Campbell wrote that Nature would allow its readers "to judge the science for themselves." Jo Webber, a London-based spokeswoman for Nature, said the journal had no further comment.

The move enraged the study's authors, who concede only minor interpretive errors.

"We certainly stand by our original, main statement and I have yet to see anyone challenge it legitimately," said Ignacio Chapela, co-author of the study with David Quist.

Nature took the unusual move after Chapela and Quist's study was severely criticized by at least four groups of scientists, many with ties to Berkeley.

"The Quist and Chapela study is a testament to technical incompetence," said Matthew Metz, of the University of Washington and a co-author of one of the two criticisms. "Evidence for the presence of transgenic DNA in Mexican maize remains dubious and empirical."

Primarily, the study's critics suggest the researchers misidentified sequences in the maize genome they believed indicated the presence of transgenic material. Particularly egregious, critics said, was their claim that the transgenic material, once it entered the maize's genome, scattered randomly, an entirely unexpected effect unseen in normal DNA.

"Since Quist and Chapela published bad science in Nature, both scientists and Nature must come absolutely clean, retract and apologize. There is no other issue," said geneticist Michael Freeling, also of Berkeley and a co-author of a critical letter published by Nature.

Nature arranged for three additional scientists, all unidentified, to review the criticisms and the researchers' reply.

All three pointed out that technical errors marred the research, according to copies of their comments obtained by The Associated Press.

However, only one called for a retraction unless further evidence for the claim could be provided advice apparently followed by Nature. The others note transgenic corn is likely growing in Mexico, but that scientific proof is still lacking.

Jane Rissler, a biotechnology critic with advocacy group Union of Concerned Scientists, said the study's shortcomings should have been detected prior to publication.

"It is important to note that we need to have the best science that we can get and that our understanding and proper dealing with genetically engineered crops is enhanced by that good science," Rissler said.

Berkeley's injection into the debate over transgenic crops is not new. In 1998, the university signed a five-year, $25 million contract with Novartis, giving the Swiss chemical company first option on much of the genomic discoveries made in its plant and microbial biology department. Critics, including Chapela, alleged conflict of interest.