One of the more acrimonious scientific debates of the decade may have ended with the publication of a study showing that genetically modified material did contaminate native corn in the crop's birthplace in southern Mexico, scientists said Wednesday.

But Elena Alvarez Buylla, author of the article published in the February edition of Molecular Ecology, said the difficult atmosphere surrounding the original debate - which threatened the reputations of some scientists - persists.

The controversy started in 2001 with an article in the journal Nature, which said that biotech genetic material had been detected in native Mexican corn in the southern state of Oaxaca, where the crop was first developed thousands of years ago.

Experts say preserving the genetic diversity of corn in Mexico is important, in case those native genes are later needed to reinforce modern varieties.

Berkeley, California, biologist Ignacio Chapela, the co-author of the 2001 article, was subject to a storm of criticism over his methodology, and Nature published an editor's note saying the evidence had not justified publishing the original article. Chapela was denied tenure after the article was published, but he later appealed and received it.

That was not the end of his woes. In 2005, an article published in the Proceedings of the National Academy of Sciences, or PNAS, found no evidence of genetic contamination.

But now, one of the authors of that 2005 study, biologist Exequiel Ezcurra, said he was convinced by Alvarez Buylla's article, which said there had indeed been very low levels of contamination. The study found evidence of the 35S Promotor, a trait widely used in genetically modified crops to promote herbicide or disease resistance.

"As far as public opinion is concerned, I do see this as a vindication," Chapela said.

Alvarez Buylla used much bigger samples, more varied genetics tests and different techniques - sampling leaves as well as corn kernels - than Chapela. Her study showed contamination varied widely depending on location, from none at all on some farm plots to as much as 10 percent of ears in a few places.

But Alvarez Buylla had to struggle to get the paper published. She said she submitted it to the PNAS but editors declined to publish it, arguing it could draw attention to political aspects of the debate, rather than the science.

The PNAS editorial board did not return calls seeking comment.

Alvarez Buylla said big questions remain: Where is the genetic contamination coming from, and how is it spread?

She suspects that some hybrid corn, possibly including some distributed by the government, may be contaminated. But she says dispassionate, objective science is the only way to determine that.