By Tim Hirsch BBC environment correspondent, in Saskatoon, Saskatchewan

[Monsanto] are blundering ahead as if there's no liability in any shape or form Jim Robbins, Saskatoon farmer

The biotechnology company Monsanto is seeking approval from Canada's government to grow a variety of GM wheat that is resistant to its Roundup weedkiller.

But farmers are threatening to take out a legal injunction to prevent the crop from being grown commercially, fearful that it could contaminate organic and conventional varieties, and taint the vitally important Canadian grain export market.

Organic farmers in Saskatchewan are already preparing a class-action lawsuit against Monsanto for making it impossible for them to grow canola (oilseed rape) on their land, since they can no longer guarantee that it is GM-free.

Contamination from herbicide-resistant canola is now so widespread, they argue, that their zero tolerance of GM content is unachievable, and they are demanding compensation.

And they fear that modified wheat will be even more difficult to control.

Closing markets

One organic wheat-grower near the city of Saskatoon, Jim Robbins, told BBC News Online: "In the case of canola, it's a done deal. I've lost it as a possible crop.

How a plant is genetically modified In pictures

"What distresses me is the talk of releasing a GM wheat. They're saying in advance that they know it's going to contaminate my crops and my fields.

"They know I have this rule that I have to meet that it can't have any GM in it, and yet they're blundering ahead as if there's no liability in any shape or form."

But the opposition to Monsanto's wheat goes far beyond the relatively small organic sector.

The Canadian Wheat Board (CWB), which markets prairie grain to the rest of the world, is now urging the company to withdraw its application.

Canola fields dot the prairies

Ken Ritter of the CWB said 82% of its customers said they did not want GM wheat, and he fears it could damage crucial export markets in places like Japan and Europe.

"Our perception from our farmer-growers is that they don't want to grow it - they're very concerned that it will cross-contaminate everything," he said.

"Our elevator systems are saying they cannot segregate it to the level required by our customers. So, if we want to continue to be a major wheat exporter, registering Roundup Ready wheat in Canada is a mistake."

Seeing benefits

Monsanto itself insists it will not push ahead with commercial planting unless and until satisfactory systems can be developed to separate the crop from conventional grain.

Monsanto says it is well aware of the segregation issue's importance

Trish Jordan, of Monsanto Canada, said: "We acknowledge the concerns that have been expressed by some farm groups.

"Conversely, we have other farmers who say 'you know what? I've seen the benefits that this technology has provided to me on my farm in canola, cotton, soybeans and corn, and I really trust that Monsanto can bring these same benefits to me with wheat'."

But with many groups in the United States also concerned about bringing GM technology to such a staple food crop, this is one battle Monsanto could find it very difficult to win.