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[SANET-MG] gm bentgrass spreads genes over a wide distance

September 23, 2004
the scientist
GM gene crosses species
Landscape sampling finds plant transgene flow into related species in
same genus 14 km away | By Cathy Holding

A genetically modified crop has passed its transgene on to a closely
related species growing 14 kilometers away and to wild-growing plants of
the same species 21 kilometers away, according to an article published
this week in PNAS.

Authors from the US Environmental Protection Agency (EPA) report that a
novel sampling method found evidence of gene flow from transgenic
Agrostis stolonifera—commonly known as bentgrass—into the related
species, A. gigantea. There was no evidence that the gene crossed into a
grass in a different genus, Polypogon monspeliensis.

Bentgrass is an amenity grass usually grown on golf courses and as a
forage crop, but it is also listed as a weed in parts of the world,
including in some parts of the United States. The transgenic strain was
engineered to contain the RoundUp (glyphosate) resistance gene CP4 EPSPS.

But researchers Anne Fairbrother and Lidia S. Watrud were not primarily
trying to assess the ecological and agronomical significance of
interspecies gene transfer. They were mainly concerned with the actual
sampling methods, which work at the landscape scale.

"We were looking at a larger scale system—both the crop system and the
way we did our sampling," said Fairbrother, from Oregon's Western
Ecology Division of the EPA. "We were also looking at naturally
occurring plants outside of agronomic systems."

The authors set up their initial hypothesis on distance and direction of
pollen travel assuming that pollen from the bentgrass can live for about
3 hours, Fairbrother told The Scientist. They devised sampling grids and
set up sentinel plants placed at different locations to act as
biological monitors.

The authors proved that resident and sentinel nontransgenic plants set
seed that had captured the transgene by testing the resistance of the
seedlings to spraying, by monoclonal antibody detection of the
resistance-conferring protein, and by sequencing of polymerase chain
reaction products in surviving plants.

The paper shows that this perennial species can "cross with its
relatives in the same area and produce glyphosate-resistant individuals
outside of where it's supposed to be," said Charles F. Chilcutt, who
authored a recent paper showing windborne gene flow from genetically
modified corn into neighboring refuges, but who was not involved in the
present study.

The results are reassuring because they mean there is no risk of
crossing with other species when growing corn or cotton in the mainland
United States, said Chilcutt, because there aren't any other species
available there.

However, the new method of sampling still may not go far enough to
accurately predict gene flow from future commercially grown transgenic
crops into the wild, commented Michael Wilkinson, at the University of
Reading's School of Plant Sciences in the United Kingdom. For
governments to make legislative decisions, the scale of predictive
modeling will have to be "even at the national level," he said.

"We have to start moving towards this kind of scale of experiments if
we're going to be predictive at all," said Wilkinson, who wasn't
involved in the study. He believes that the current article will help
the EPA and others to assemble spatially explicit models on much larger
scales in the future.

"But it's not hugely predictive at this stage because they're not really
in a situation yet where they're able to model gene flow from the kind
of patterns of distribution you'll expect once these plants are actually
commercialized—if they will be," Wilkinson added.
Links for this article
L.S. Watrud et al., "Evidence for landscape-level, pollen-mediated gene
flow from genetically modified creeping bentgrass with CP4 EPSPS as a
marker," PNAS, DOI:10.1073/pnas.0405154101, September 20, 2004.

US Environmental Protection Agency

Anne Fairbrother

Lidia S. Watrud

Charles F. Chilcutt

C. Holding, "Resistance found in GM refuges," The Scientist, May 11 2004.

Michael Wilkinson

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