Wheat in Chicago fell the most in two weeks after Japan suspended imports from the U.S., where the government discovered an unapproved, genetically modified strain growing in an Oregon field.

Japan, the biggest buyer of U.S. wheat behind Mexico, suspended imports of western-white wheat and feed wheat from the U.S., said Hiromi Iwahama, the director for grain trade and operation at the agriculture ministry. Scientists said the rogue wheat in Oregon was a strain tested from 1998 to 2005 by Monsanto Co. (MON), the world’s top seedmaker. Japan also canceled a purchase of 24,926 metric tons of white wheat.