The spread of transgenic canola pollen for as much as 3 km from a field 
means that organic or non GM  cannot be grown in areas such as western 
Canada or  Northern USA.

Science Jun 28 2002: 2386-2388

Pollen-Mediated Movement of Herbicide Resistance Between Commercial 
Canola Fields

Mary A. Rieger, Michael Lamond, Christopher Preston, Stephen B. Powles, 
and  Richard T. Roush

There is considerable public and scientific debate for and against 
genetically modified (GM) crops. One of the first GM crops, Brassica 
napus (oilseed rape or canola) is now widely grown in North America, 
with proposed commercial release into Australia and Europe. Among 
concerns of opponents to these crops are claims that pollen movement 
will cause unacceptable levels of gene flow from GM to non-GM crops or 
to related weedy species, resulting in genetic pollution of the 
environment. Therefore, quantifying pollen-mediated gene flow is vital 
for assessing the environmental impact of GM crops. This study 
quantifies at a landscape level the gene flow that occurs from 
herbicide-resistant canola crops to nearby crops not containing 
herbicide resistance genes.
A Little Pollen Goes a Long Way
Erik Stokstad

One of the major concerns about genetically modified (GM) crops is that 
they might spread their genes to nearby weeds or organic crops. Some 
governments have responded by recommending that GM crops be planted in 
isolation, or by setting limits on GM material in organic or 
conventional crops. But they have had few data to go on. Now a 
comprehensive study, described on page 2386, provides some hard numbers 
on the movement of pollen between fields, with implications for 
regulators. "These are real-world data that can be used for real-world 
decisions," says Paul Raymer, an agronomist at the University of 
Georgia, Griffin.

A team led by reproductive ecologist Mary Rieger of the Cooperative 
Research Center for Australian Weed Management and the University of 
Adelaide in Australia reports that canola pollen can travel considerable 
distances but that the amount of gene flow is minimal. Although the 
findings reinforce the difficulty of growing GM-free crops, they also 
suggest that the levels of gene diffusion are below European standards 
for contamination of conventional food.

Over the last decade, a handful of small experiments has indicated that 
a minuscule amount of pollen from engineered crops can spread up to a 
few hundred meters. But what happens on real farms was unclear. To find 
out, Rieger and her colleagues at the University of Adelaide and the 
University of Western Australia in Nedlands took advantage of a unique 
opportunity. In 2000, Australian farmers for the first time planted 
varieties of canola with resistance to acetolactate synthase-inhibiting 
herbicides. (These crops are not GM varieties but instead were created 
by mutagenesis.) Working in three states and under various climatic 
conditions, Rieger's team collected seeds from 63 nearby fields planted 
with conventional canola.

The herbicide-resistance trait spread to 63% of the conventional fields, 
including some up to 3 kilometers away from the source. The percentage 
of resistance among seed samples ranged up to nearly 0.2%, but when 
averaged per field, the highest percentage was 0.07%. The harvests from 
the vast majority of fields contained less than 0.03%.