The journal Nature has announced that a report claiming that genetically engineered DNA had found its way into wild Mexican corn should not have been published. The announcement, unveiled online last Thursday, came with two critiques of the study and a rebuttal by its authors. Although they are not retracting the original article, Nature editor Philip Campbell states that the journal has decided to make the circumstances surrounding it clear and "allow our readers to judge the science for themselves."

The paper in question, by David Quist and Ignacio H. Chapela of the University of California at Berkeley appeared in the November 29, 2001, issue of the journal. In it, the team reported that native corn from the southern Mexico state of Oaxaca contained genetically modified material, despite a country-wide ban on engineered corn since 1998. They further posited that the genes spliced into the plants were unstable and scattered around the genome in unpredictable ways.

It was this second conclusion that provoked the most reproach. "The discovery of transgenes fragmenting and promiscuously scattering throughout genomes would be unprecedented and is not supported by Quist and Chapela's data," contend Matthew Metz of the University of Washington and Johannes Futterer of the Institute of Plant Sciences in Switzerland in the first criticism on the Nature Web site. They suggest that Quist and Chapela incorrectly interpreted results of a technique known as inverse PCR (i-PCR), which allows scientists to examine a stretch of unknown DNA that lies adjacent to an identified section. The technique, Quist and Chapela's detractors say, is prone to artifacts and misinterpretation. "Transgenic corn may be being grown illegally in Mexico," write Nick Kaplinsky of the University of California at Berkeley and his colleagues in the second critique, "but Quist and Chapela's claim that these transgenes have pervaded the entire native maize genome is unfounded."

Quist and Chapela disagree, however. In their rebuttal, they present new data and contend that it "confirms our original detection of transgenic DNA integrated into the genomes of local land races in Oaxaca." Yet they do concede that some of the concerns pertaining to the i-PCR technique--and hence the assertion that the foreign genes are dispersed around the genome--are well founded.

Consensus on this issue may well prove elusive, especially in light of the tempestuous debate already surrounding genetically modified foods and biotechnology. But further study is warranted because, as Kaplinsky and his colleagues point out, "it is important for information about genetically modified organisms to be reliable and accurate, as important policy decisions are at stake."