DES MOINES, Iowa (AP) — Farmers and farm businesses in 20 states have now filed more than 360 lawsuits against agricultural chemicals-maker Syngenta, and hundreds more may be coming as a federal judge organizes the complex case so they can move forward.

The dispute centers around Syngenta's sale of a corn seed called Agrisure Viptera, which was genetically altered to contain a protein that kills corn-eating bugs such as earworms and cutworms. The U.S. Department of Agriculture approved it in 2010, and Syngenta first sold it to farmers in 2011.

China, a growing importer of U.S. corn that refuses to buy genetically modified crops it hasn't tested, had not approved Viptera when Syngenta began selling it. In November 2013, China discovered the Viptera corn trait in several U.S. shipments.

It began rejecting U.S. corn imports in February 2014. The lawsuits say it rejected more than 131 million bushels.