An escaped strain of transgenic grass bred for golf courses could wreak havoc on native grassland species in the northwestern United States, ecologists are warning.

The strain, which was growing in a test plot in Oregon and hadn't yet been approved for use by the US Department of Agriculture (USDA), has now been detected in the wild, up to 3.8 kilometres outside the test area. While the transgenic component of the plant might not in itself pose a problem, the hardy strain could replace many other native grasses if it gains a foothold, ecologists say

Scientists working for the US Environmental Protection Agency (EPA) in Corvallis, Oregon, have been monitoring the region surrounding the experimental plots where the plants, called creeping bentgrass (Agrostis stolonifera) were being grown

The EPA team studied areas of grass within almost 5 kilometres of the experimental plot. As they report in a forthcoming issue of Molecular Ecology, of 55 sites examined, six contained descendants of the transgenic test plants. The researchers believe that seeds and pollen from the test site were dispersed by the wind

EPA officials stress that the scale of the problem is not yet known. "It could persist in the wild, but we wouldn't necessarily expect it to have an advantage," says Jay Reichman, one of the scientists who tracked down the grass in the wild. "Its impact remains to be seen."

The USDA has started a full environmental impact assessment of the plant.

Roundup resistant

It is not clear what advantage, if any, the grass's transgenic status will give it in the wild. The strain, bred by The Scotts Company, based in Marysville, Ohio, was engineered to be resistant to the herbicide glyphosate, also known as Roundup. This means that it would be difficult to eradicate from areas where other grasses are grown and managed with herbicides.

More pressing is the effect that the grasses might have on other local grass species, says Tom Stohlgren, an ecologist at the US Geological Survey's National Institute of Invasive Species Science in Fort Collins, Colorado. Plants of this type, called 'sod-forming' grasses, can spread rapidly because they can reproduce sexually, through widely dispersing pollen and seeds, and also asexually, by forming a dense mat of roots from which more shoots emerge.

Although bentgrass would be unlikely to encounter herbicide in the wild, so its transgenic status wouldn't necessarily be an issue, it might still plough down native grasses. "Sod-forming grasses can tend to outcompete other species," he explains. "It doesn't need to sexually reproduce - it's like The Blob. It could potentially hit rare species or national parks."

Long-distance travel

Distances of a few dozen kilometres won't be enough to stop a tenacious grass, Stohlgren adds. Grasses, unlike food crop plants, are perennial, meaning that they survive from one year to the next. And their seeds are so fine that they can easily be transferred from place to place by the wind or by sticking to animals, people or vehicles.

Oregon's grass-seed industry, which produces some 70% of seed for US gardeners and groundskeepers, is based in Willamette Valley, about 90 kilometres away from the test site. If the bentgrass reaches here, it would be very hard to eliminate.

Grasses have mounted widespread invasions before, Stohlgren says. In 1998, he showed how Kentucky bluegrass (Poa pratensis) had swept through Wind Cave National Park in South Dakota, tearing through habitats that previously contained a diverse range of grasses. Kentucky bluegrass can now be found in every state in the country.

The rampant spreading ability of bentgrass could also pass on the transgene for Roundup resistance to other grass species through hybridization, Stohlgren adds. "We've broken down the barriers - things happen so fast," he says. "It's like Darwin on steroids."

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