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Wind moves pollen with altered genetic traits beyond fields of experimental bentgrass

Creeping bentgrass (Agrostis solonifera L.) is one of the first perennial wind-pollinated crops being commercially developed for genetic resistance to the widely used herbicide, RoundUp®. It is a valuable, high-maintenance crop that if properly watered, mowed, aerated and fertilized forms a perfect carpet for golf balls. However, unlike most of the transgenic crops that have been commercialized in the United States, creeping bentgrass can cross breed with native grasses that grow in areas where the grass will be commercially produced or where it is likely to be used on golf courses. This has raised questions about potential ecological risks associated with the use of genetically engineered crops and highlighted the need for rigorous methods to use in the regulatory risk-assessment process.

Field and laboratory research by Western Ecology Division (WED) scientists has found that pollen from genetically modified (GM) bentgrass travels much farther than previously measured. Results of this research by Dr. Lidia S. Watrud and colleagues in WED’s Risk Characterization Branch were published in the Oct. 5 issue of Proceedings of the National Academy of Sciences. This paper documents gene flow at the landscape level from a seed company’s experimental fields in Central Oregon to 75 of 138 “sentinel” plants placed to collect any drifting pollen, and to 29 of 69 genetically compatible resident grass plants. They found that pollen from the transgenic grass, estimated to be viable for up to three hours, traveled up to 13 miles from the experimental fields. However, most of the gene flow occurred within a mile and a quarter downwind of the experimental fields.

Because creeping bentgrass is an important seed crop in western Oregon’s Willamette Valley, the GM bentgrass in this study was grown east of the Cascade Mountains in irrigated fields on a plateau above the Deschutes River to reduce the possibility of accidental cross-pollination with conventional grass crops. (Location of the experimental fields was more than one hundred miles east of the fields in the Willamette Valley where non-resistant, non-GM creeping bentgrass is commercially grown.)

Eight experimental fields of the GM bentgrass flowered for the first time in the summer of 2003. Beyond the fields in a carefully designed sampling grid, WED researchers deployed 178 pots containing non-GM creeping bentgrass as “sentinel” plants. Viable pollen drifting from the experimental fields to these compatible monitoring sentinel plants could be expected to transfer RoundUp® resistance to grass grown from seeds of the monitor plants.

In the sampling area, the researchers also studied naturally occurring compatible resident grasses, which could form hybrids with the GM bentgrass. Concerns cited by agricultural scientists about introducing a herbicide-resistant gene to creeping bentgrass include GM bentgrass persisting and spreading as a weed, and movement of the introduced gene to other compatible species.

After the GM bentgrass in the experimental fields had finished flowering, researchers bagged the panicles, or seed heads, of the sentinel plants. They also bagged and collected panicles of resident grasses.

After harvesting the seeds from sentinel plants and the related resident grasses, researchers planted them in a greenhouse. When the young seedlings had developed two leaves, they were sprayed with a field application of RoundUp® herbicide. RoundUp®, which contains the active ingredient glyphosate, is a broad spectrum herbicide used widely to control unwanted vegetation.

About two weeks later seedlings that survived that spraying were sprayed again with an application twice as strong. The surviving seedlings were presumed to be carrying the gene from the experimental GM fields that made them resistant to RoundUp®, but the scientists confirmed that assumption with additional tests for the protein CP4 EPSPS produced by the engineered gene and the DNA that encoded the engineered protein. They used PCR (polymerase chain reaction) and DNA sequencing to further confirm the presence of the engineered trait in the test seedlings.

WED scientists expressed some surprise that live pollen drifted as far as it did. Earlier published studies assessed gene flow from plots that included no more than a few hundred plants demonstrated live pollen movement to approximately 1,200 feet.
Developers of the genetically modified grass seed have sought U.S. Department of Agriculture permission to market it. Its resistance to the RoundUp® herbicide would allow golf courses to more easily control weeds on golf greens and fairways.

Scientists performing the research included Dr. Watrud, WED ecologist and geneticist; Dr. E. Henry Lee, WED biological statistician; Dr. Anne Fairbrother, Chief of WED’s Risk Characterization Branch; Connie Burdick, WED Geographic Information Systems specialist; and Dr. Jay R. Reichman, postdoctoral molecular biology fellow at WED. Mike Bollman, Marjorie Storm, and Dr. George King, plant ecologists with Dynamac Corp.; and Dr. Peter K. Van de Water, a postdoc with the USGS Forest and Rangeland Ecosystem Science Center in Corvallis, also took part in the study design and analysis.
Environmental risk assessment of genetically modified crops is of vital interest to regulators, the agricultural industry, scientists, and the general public. WED scientists are continuing to examine implications to the environment of GM crops. (Contact L.S. Watrud, 541-754-4874, watrud.lidia@epa.gov)

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