China Rejects GMO American Corn
By: Amy Jeanroy
Published: December 8, 2013

China rejected a 60,000 ton shipment of American corn because it included genetically modified grain. A special variety developed by Syngenta called MIR162, was detected in the shipment. 
According to the Los Angeles Times, the U.S. is the world's largest corn exporter, and China is our number 3 customer. 
For more on this, see the original piece at LA Times Business: 
China Rejects Shipment of U.S. Genetically modified corn