Gene Flow in Bentgrass
A recent publication documents gene flow on a landscape level from creeping bentgrass (Agrostis stolonifera), one of the first wind-pollinated, perennial, and highly out-crossing transgenic
crops being developed for commercial use. Most of the gene flow occurred within 2 km in the direction of prevailing winds. The maximal gene flow distances observed were 21 km and 14 km in sentinel and resident plants, respectively, that were located in primarily nonagronomic habitats. The selectable marker used in these studies was the CP4 EPSPS gene derived from Agrobacterium spp. strain CP4 that encodes 5-enol-pyruvylshikimate-3-phosphate synthase and confers resistance to glyphosate herbicide. Evidence for gene flow to 75 of 138 sentinel plants of A. stolonifera and to 29 of 69 resident Agrostis plants was based on seedling progeny survival after spraying with glyphosate in greenhouse assays, positive TraitChek®, PCR, and sequencing results.
Norman C. Ellstrand, an expert on this subject at the University of California, Riverside, who was not involved in the study but read the paper, was quoted as saying, "It's the longest distance gene-flow study that I know of. The gene really is essentially going to get out," he added. "What this study shows is it's going to get out a lot faster and a lot further than people anticipated."
One reason the grass pollen was detected so far downwind was the size of the farm - 400 acres with thousands of plants. Most previous studies of gene flow have been done on far smaller fields, meaning there was less pollen and a lower chance that some would travel long distances. Those small studies, the new findings suggest, might not accurately reflect what would happen once a plant covers a large area.
Cindy Smith, who is in charge of biotech regulation at USDA, was cited as saying that after hearing public comments earlier this year, the department has now decided to produce a full environmental impact statement, which could take a year or more, and that the new study "gives some preliminary information that's different from previous studies that we're aware of" but more conclusive research is needed. One of the companies developing this grass, Scotts, was cited as saying that because naturally occurring bentgrass has not caused major weed problems, the bioengineered version would pose no new hazards. Any Roundup®-resistant strains that might somehow develop outside of intentionally planted areas could be treated with other weed killers. Scotts is also developing genetically modified grass for home lawns, like slow-growing types that would need less mowing. But a Scotts scientist was cited as saying those products still need several more years of testing, and that the company would avoid types of grass that could become weeds, adding, "We don't want to put a product out there that is going to be a threat."
The company has received some support for their argument from the Weed Science Society of America (WSSA), a professional group, which conducted a review of the weed tendencies of creeping bentgrass and its close relatives at the request of the Department of Agriculture. In summarizing the conclusions of the review, Rob Hedberg, director of science policy for WSSA, was quoted as saying, "In the majority of the country these species have not presented themselves as a significant weed problem, historically," and that’s because people have generally not tried to control bentgrass and similar species with Roundup®, known generically as glyphosate, "the inability to control them with this herbicide is a less significant issue." Still, the society's report noted that bentgrass could be considered a weed by farms that are trying to grow other grass seeds. (PNAS Vol. 101 No. 40 p.14533-14538 & NY Times/Knight-Ridder Tribune, 9/21/04).
