GLOBAL grain buyers are marking down the price of Australia’s genetically modified canola as the European market shuts the gate on GM crops. The Australian Wheat Board is offering to buy up supplies of GM canola at guaranteed prices. Global agribusiness giant Monsanto -- which produces ”Round-up Ready” canola, genetically modified to survive sprayings by its trademarked weed killer -- has told GM canola farmers they will lose no more than $10 a tonne for product delivered to agricultural company Cargill’s crush facility at Newcastle by June 29.