Alan Tracy, president of U.S. Wheat Associates, which represents wheat exporters, downplayed the Montana discovery. "We don't expect any reaction" from wheat buyers, he says, because the GM wheat was found at a research station, rather than a commercial field.
The 2013 discovery, on the other hand, rocked wheat markets. The genetically modified grain was never approved for sale, and it's unwelcome in countries that buy U.S. grain. Since it was found in a commercial wheat field, foreign buyers worried that GM wheat might have contaminated the entire American harvest, just as unapproved GM rice did in 2006. Japan and South Korea stopped buying U.S. wheat for a time.
Tests relieved those worries. GM wheat was never found anywhere else — not in commercial seed, nor in shipments of grain. Normal trade resumed.
But these tests only deepened the mystery. Where had this wheat come from? Investigators from APHIS interviewed farmers and took samples of wheat seed throughout the wheat-growing areas of Oregon and Washington, looking for clues.
They also carried out genetic analysis of the wheat that was found in the farmer's field, hoping to match it with a specific variety of wheat, and thus with a particular field trial in which that type of wheat was grown. (Monsanto carried out numerous field trials of GMO wheat until 2005, when it cancelled the program.)
No clues emerged. The genetic tests showed that this GM wheat was a genetic mixture of different types of wheat. Wheat breeders create such mixtures in the course of their work, but seed companies don't sell them or carry out field trials of them.
Monsanto's chief technology officer, Robert Fraley, floated his own hypothesis in a teleconference with reporters last year. "The fact pattern indicates the strong possibility that someone intentionally introduced wheat seed containing [Monsanto's new gene] into his field," he said at the time. He speculated that this could have been an act of sabotage carried out by anti-biotech activists who somehow had acquired genetically engineered seed.
USDA investigators declined to endorse that scenario. "We were not able to determine how it took place," says Bernadette Juarez, who led the APHIS investigation.
Carol Mallory-Smith, a professor of weed science at Oregon State University, said that the rogue wheat — and other cases in which genetically modified crops have wandered far afield from their designated research plots — show that APHIS needs to monitor field trials of genetically modified crops more carefully.
People also need to realize that plant genes are likely to persist in the environment, once they're planted in open fields, she says.
"Any time a new trait is put into the environment, there's really no way of retracting that gene or bringing it back and saying, 'We've changed our mind,' " she says.