South Korean millers suspended imports of U.S. wheat on Friday and some Asian countries stepped up inspections after the discovery of an unapproved strain of genetically modified wheat in the United States, but stopped short of imposing import bans. U.S. officials are racing to quash global alarm in the wake of news the strain of wheat, developed by biotech giant Monsanto, had been found in an Oregon field late last month. The discovery has already prompted major buyer Japan to cancel plans to buy U.S. wheat, while the European Union said it would step up tests. South Korea—which last year sourced…