The discovery of an unlicensed strain of genetically modified wheat in an Oregon field has caused widespread concern amongst farmers in the United States that trading partners could reject wheat shipments if they are found to be contaminated with the wheat.

The resistant wheat was discovered by an Oregon farmer and sent to a nearby university laboratory for testing after it survived applications of glyphosate herbicide. The plant was found to be of a GM herbicide-resistant variety, developed by Monsanto and trialled in the United States between 1998 and 2005.

US Department of Agriculture broke news of the plant's discovery on Wednesday (29th May). Though the crops were trialled for several years, their licensing was never completed as the seeds were never sold commercially. To date, no GM wheat plants have been developed for commercial use.

On Thursday (30th May), Japan suspended wheat imports in response to the USDA announcement, pending the results of a US government investigation into how the plant came to be growing in the North-Western state. The GM variety was last trialled in the US eight years ago, and Monsanto has suggested trial sites in Oregon were a long distance from where the wheat was found growing.

Growers in the region are especially concerned as the North-West predominantly produces soft white wheat of the type Japan suspended last week. On Friday (31st May), South Korea also suspended imports pending the results of government tests to be conducted this week. A third Asian importer, Taiwan, announced on Monday that it will be investigating imports. Asia is home to five of the top ten buyers of US wheat.

EU authorities said they have requested more information from USDA, including a means of testing for the GM wheat, but as yet there has been no suspension of imports.

In 2006, contamination of the US rice crop with an unapproved variety of GM rice led to bans on rice imports from Europe and Japan and cost agribusiness Bayer CropSciences dearly.

On Thursday, The USDA released its fourth Outlook for U.S. Agriculture Trade in 2013. The department predicts that the US will export $139.5 billion in agricultural commodities this financial year. If realized, this would be a new record.

Upon the Outlook's release, Agriculture Secretary Tom Vilsack said, "Today's report is promising news that keeps American agriculture on track to continue the strongest period of exports in our nation's history. Agricultural exports are an important part of our economy, supporting more than one million jobs… USDA has worked hard to open new markets for quality U.S. agricultural products."

Although Secretary Vilsack did not mention the discovery in the North-West, USDA spokesperson Michael Firko said earlier in the week, "We are taking this situation very seriously and have launched a formal investigation. Our first priority is to as quickly as possible determine the circumstances and extent of the situation and how it happened.  We are collaborating with state, industry, and trading partners on this situation and are committed to providing timely information about our findings."