The report rattled US wheat markets. In addition to Japan's action, the European Union, which imports more than a million tonnes of US wheat a year, said it was following developments ''to ensure EU zero-tolerance policy is implemented''. It asked Monsanto to help detection efforts in Europe. The issue focuses attention on St Louis-based Monsanto, a $US56 billion company with more than $US13.5 billion in sales of seeds, services, weed killer and biotechnology to the agriculture industry. In the face of mounting protests, including public demonstrations in multiple cities last weekend, the company has stood behind its other genetically modified products. Many food safety advocates and environmental groups say that more testing needs to be done to ensure that genetically modified seeds are not harmful to health. In addition, they say, the genetic engineering of crops has encouraged the more widespread use of herbicides and led to the development of weeds more resistant to those herbicides. The US already relies heavily on genetically modified crops. Corn, cotton and soybeans have gone from 5-17 per cent of the US market in 1997 to between two-thirds and more than 90 per cent in 2012. By some estimates, more than 70 per cent of processed foods sold in the US contain ingredients and oils from genetically engineered crops.

A 2008 US Government Accountability Office report estimated the value of the global market for genetically engineered seeds was $US6.9 billion. Though altered seeds are made by four other leading agricultural businesses, Monsanto relies most heavily on such products, experts say. But Americans remain sceptical about some genetically modified foods, including proposals to cultivate altered salmon. And big agriculture companies have avoided commercial development of genetically engineered wheat because about half of the US wheat crop is exported, and governments in major markets such as the European Union, Japan and China are opposed to genetically modified wheat seed. Monsanto said in a statement that it ended commercial development of the strain of wheat found in Oregon nine years ago. The company said about 23 million hectares of wheat was planted in the US every year, and that while the Agriculture Department's test results in Oregon ''are unexpected, there is considerable reason to believe that the presence of the Roundup Ready [herbicide-resistant] trait in wheat, if determined to be valid, is very limited''. But food safety groups drew the opposite conclusion. ''This was not from a recent trial, which means it's been sitting there in the environment,'' said Andrew Kimbrell, executive director of the Centre for Food Safety, a non-profit group. ''It's highly doubtful that it's just on one farm. If it's out there, it's out there.'' The centre's science policy analyst Bill Freese added, ''It has been 12 years since this wheat was grown officially in Oregon. It doesn't just disappear and magically appear 12 years later.''

Freese added that Monsanto had 15 new permits, issued in 2011, to test herbicide-resistant wheat in Hawaii and North Dakota, including an unusually large 121-hectare field in North Dakota. Freese said the size of that field would make it difficult to prevent accidental spread. Monsanto spokesman Tom Helscher said the new field tests involved ''different herbicide traits'' than the genetically modified strain found in Oregon. He said they were ''focused on preventing yield loss due to disease and other environmental stressors''. He said the company had a project in early development that would boost yields and provide crops with a ''strong tolerance'' to existing herbicides. ''We talk to people in the wheat industry and they say they need tools to help deal with problems they face, whether weed or insect control,'' he said. ''We wouldn't expect to have a product for quite a number of years.'' Part of the battle over genetically modified seed has been taking place in Washington.

Monsanto and other companies have been pressing members of Congress to vote against measures that would require disclosure for food made with genetically modified or engineered crops. Friends of the Earth said 64 countries had similar rules and that 37 bills had been introduced in 21 states this year proposing that genetically engineered foods be labelled. Monsanto is also urging lawmakers in the Senate to vote for a rider continuing a resolution that would strip federal courts of the power to provide injunctive relief to environmental and food activists seeking to stop the spread of such crops. Genetically modified crops have a history of provoking bans by trading partners. In 2006, the Department of Agriculture announced that trace amounts of a genetically engineered rice had been commingled with supplies of conventional rice. That led several US trading partners to reject US rice, causing losses for US farmers and exporters.

WASHINGTON POST