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Unintended Effects of Genetic Manipulation

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Spread of herbicide-resistance from genetically modified creeping bentgrass into the wild.

Manipulated Organism: Creeping bentgrass (Agrostis stolonifera L.).

Inserted Transgenes and Intended Effect: CP4 EPSPS gene derived from the common soil bacterium Agrobacterium sp. (strain CP4) to convey resistance to the herbicide glyphosate. The gene was fused to the cauliflower mosaic virus (CaMV-35S) promoter so that the gene would be expressed in all parts of the plant. Creeping bentgrass is a widely used golf course grass. Monsanto and Scotts Company developed the herbicide-resistant variety with this market in mind.

Goal of These Studies: Investigate whether the herbicide resistance gene in glyphosate-resistant creeping bentgrass (GRCB) can spread into the wild through seeds, pollen, or shoot segments (stolons). These studies were carried out in Jefferson County, Oregon, around an Oregon Department of Agriculture control area where in 2002 in a field trial Scotts Company had planted 162 ha (400 acres) of transgenic creeping bentgrass which flowered in 2003. GRCB was the first genetically engineered plant in the U.S. for which an environmental impact statement was requested; the planting was done under a USDA permit. The studies were carried out by the U.S. Environmental Protection Agency and university scientists (see below).

Results of these Studies: The transgene escaped into the wild by seeds (which are very small and light - about 13,500 seeds weigh one gram) and by pollen.

Watrud et al. (2004) found that the herbicide-resistance transgene spread via pollen to an area up to 21 km (13 miles) beyond the control area perimeter and had pollinated wild creeping bentgrass as well as a close relative (redtop, Agrostis gigantean). 53% of the creeping bentgrass plants investigated had offspring that were herbicide-resistant; most of these plants were found in a 2.1 km (1.3 mi.) area outside and downwind of the control area.

The 162 ha of GRCB were taken out of production after seed harvest in 2003; a small 2.4 ha (6 acres) area was planted that year and seeds were harvested in 2004. No more planting of GRCB occurred after that. In 2004 and 2005 Reichmann et al. (2006) did a survey of an area outside the control area perimeter and detected nine creeping bentgrass plants that tested positive for herbicide resistance. They were found up to 3.8 km (2.4 mi.) beyond the control area, and the authors conclude that there was both seed dispersal and pollen-mediated crossing with wild creeping bentgrass.

Using other methods, Zapiola et al. (2008) carried out a study from 2003 to 2006 in which they surveyed areas outside the control perimeter for GRCB. In 2003 they found no transgenic plants, but in 2004, 2005 and 2006 they found many: of the creeping bentgrass tested, in 2004 93%, in 2005 54%, and in 2006 62% were glyphosate resistant. The plants were found in an area up to 4.6 km ( 2.9 mi.) beyond the area were the GM plants had originally been grown. The authors believe that this transgene spread occurred mainly via seed dispersal.

Additional Comments: Creeping bentgrass is an outcrossing grass and part of a hybridizing network of at least twelve other grass species of Agrostis and Polypogon, four of which grow wild in central Oregon. Agrostis species are flexible and variable in their morphology and grow in a variety of agronomic and nonagricultural environments.

Zapiola et al. remark that it is "unrealistic to think that a transgene could be contained in an outcrossing, wind-pollinated, small-seeded, perennial crop, even with expanded isolation distances and stringent production practices" (p. 5). Moreover, since many specimens of transgenic creeping bentgrass were found three years after the large field trial, the "elimination of transgenes is unlikely to be feasible," especially since within the control area "an intense and extended mitigation program had been initiated and is still underway [by The Scotts Company]" (p. 7).

In November 2007 the USDA reached a settlement with The Scotts Company, which agreed to pay a $500,000 civil penalty for failing to comply with "performance standards and permit conditions" and for accidental release of the transgenic bentgrass in the 2003 field trials (USDA News Release No. 0350.07).

Sources: Reichman, J., L. Watrud, E. Lee, C. Burdick et al. (2006). "Establishment of Transgenic Herbicide-Resistant Creeping Bentgrass (Agrostis stolonifera L.) in Nonagronomic Habitats," Molecular Ecology vol. 15, pp. 4243-55.

Watrud, L., E. Lee, A. Fairbrother, C. Burdick et al. (2004). "Evidence for Landscape-level, Pollen-mediated Gen Flow from Genetically Modified Creeping Bentgrass with CP4 EPSPS as a Marker," PNAS vol. 101, pp. 14533-38.

Zapiola, M., C. Campbell, M. Butler, and C. Mallory-Smith (2008). "Escape and Establishment of Transgenic Glyphosate-resistant Creeping Bentgrass (Agrostis stolonifera) in Oregon, USA: A 4-year Study," Journal of Applied Ecology doi: 10.1111/j.1365-2664.2007.01430.x

Author Affiliations: Reichman et al.: Western Ecology Division of the U.S. Environmental Protection Agency; Dynamac Corporation; Oregon State University, Department of Crop and Soil Science, Corvallis.

Watrud et al.: Western Ecology Division of the U.S. Environmental Protection Agency; Dynamac Corporation; U.S. Geological Survey, Corvallis, Oregon.

Zapiola et al.: Oregon State University, Corvallis; Oregon State University, Central Oregon Agricultural Research Center, Madras.

Funding: U.S. Environmental Protection Agency (Reichman et al. and Watrud et al.); USDA grants, Scotts Company (Zapiola et al.).

Product Status: Not on the market as of January 2008. Monsanto and Scotts Companies have petitioned the USDA to deregulate their glyphosate-resistant creeping bentgrass so that it can be sold commercially. The petition is under consideration by the USDA.

Copyright 2008 The Nature Institute.

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