UMass Magazine Online

Winter 2005

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A New Kind of Farm a New Breed of Farmer

Dear One Absent This Long While

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The Great Transgene Escape
Allison Snow discovered that some weeds are getting a free ride

—Doug McInnis




	Allison Snow ’82G

SCIENCE BOASTS MANY ACHIEVEMENTS, but eradication of the common weed isn’t yet among them. Now some weeds could pick up a new survival skill—resistance to one of the most effective herbicides, Monsanto’s RoundUp.

This could be the harbinger of a worldwide profusion of superweeds. We have advance warning of the problem thanks to Allison Snow ’82G, one of a small number of biologists documenting the flow of genetically engineered traits from food crops to closely related weeds. Snow, along with Dr. Diana Pilson of the University of Nebraska and Dr. Loren Riesberg of Indiana University, discovered that pest resistance can be passed from engineered crops to related weeds and that those traits could persist indefinitely.

Herbicide resistance is one of the most problematic examples. Geneticists have engineered some food crops so that they aren’t harmed by RoundUp. That means farmers can douse their fields with the highly effective herbicide without killing crops. This works well—unless the resistance jumps to related weeds, a process called transgene escape.

“Theoretically, you could create crops and related weeds with a host of properties, such as salt tolerance, drought resistance, pest resistance, herbicide resistance, and tolerance to cold and heat,” says Snow, professor of biology at Ohio State University. “These traits are self-replicating. Once you get them into a weed, you can’t take them back.”

So far the problem has been minimal for domestic agriculture, in part because just a handful of genetically engineered food crops have earned federal approval for commercial use. These include herbicide-resistant soybeans and canola, and corn and cotton with built-in pest-control agents. But, says Snow, 50 other crops have been genetically engineered in labs and in the long run perhaps 100 food crops, as well as trees, shrubs, and grasses, are candidates for engineering.

The work of Snow and her colleagues suggests that a large problem is in the offing. Weeds soak up nutrients needed by food crops. Virtually indestructible weeds would impact worldwide food harvests. Snow’s work has been written about in such publications as National Geographic magazine, the New York Times, and the Washington Post, increasing awareness about the potential pitfalls.

“Her work has global implications—implications anywhere that people want to grow food,” said biology professor Paul Godfrey, Snow’s thesis advisor at UMass Amherst. The fight to take on superweeds is in able hands, says Godfrey; Snow was one of the best graduate students he saw in his 35 years at UMass Amherst. “Of the many theses I have read, hers was the only one in all the years I taught that required no corrections. It was perfect.”

Snow first began taking courses at UMass Amherst while she was an undergraduate at Hampshire College. She was so impressed by Godfrey’s course in coastal ecology that she enrolled for graduate school.

After graduation, Snow noticed that few scientists were focused on the potential problems of genetic engineering of food crops. She decided to take a look.
Part of her work is done at Ohio State’s well-equipped labs and greenhouses. But much takes place in the field—studying sunflowers in the Great Plains, or traveling to Vietnam and China to study rice production. Both rice and sunflowers are candidates for genetic engineering.

Snow says transgene escape wouldn’t be a problem for some crops in the United States because they have no weedy relatives here; corn is an example. But that doesn’t hold true in some foreign countries, where weedy relatives of corn are common. Canola, which has been genetically modified for herbicide resistance, does have weedy relatives in North America, and canola growers are already contending with herbicide-resistant weeds.

In such situations, Snow offers a commonsense solution: If there are related weeds nearby, don’t plant the types of genetically modified crops that could help weeds get stronger. “When a crop grows near its weedy relatives,” she said, “it’s inevitable that the genetically engineered trait will move into the weed.”

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