GMO labeling debate puts food industry on defensive

Roberts has framed the debate as an economic issue, not a matter of safety, and noted the regulatory oversight already in place from three federal agencies: The U.S. Department of Agriculture's Animal and Plant Health Inspection Service, the Environmental Protection Agency and the Food and Drug Administration.

Opponents of Roberts' bill have dubbed it -- and a similar bill that passed the House last summer -- as the Denying Americans the Right to Know or DARK Act. Many of them support an opposing bill, sponsored by Sen. Jeff Merkley, D-Ore., which would establish a national standard for mandatory labeling.