Trading giant Cargill said in court documents on Friday that it had lost more than $90 million because Syngenta sold Agrisure Viptera corn, known as MIR 162, to U.S. farmers without first obtaining import approval from China, which has turned away boatloads of U.S. crops containing the variety over the past year. The lawsuit will be a test case of who is ultimately responsible for such rejections that damage international trade: the seed companies that develop unapproved GMO traits or the merchants who sell grain that may be contaminated with it.