In a fight that highlights global sensitivity over genetically modified crops, Cargill Inc. sued Syngenta AG SYNN.VX -0.56% , claiming that the Swiss seed maker’s push to sell bioengineered corn seeds that weren’t approved in China cost the U.S. grain company $90 million when Beijing rejected corn shipments.

The suit, filed on Friday in Louisiana state court, escalates tensions that have shaken U.S. agribusiness since China last year sharply curtailed imports of U.S. corn. Beijing’s move all but closed off a major market for the grain, contributing to a sharp decline this year in prices for the U.S.’s biggest crop by value and costing shippers hundreds of millions of dollars, according to U.S. grain groups.

China’s government began rejecting U.S. corn shipments in November after its tests found that some shipments of U.S. corn contained Agrisure Viptera, a genetic modification developed by Syngenta that enables the plants to produce proteins that ward off pests. China hasn’t approved the product, although Syngenta says it applied for approval in 2010.

Cargill’s suit accuses Syngenta of acting irresponsibly by selling the seeds to U.S. farmers before Syngenta secured Chinese approval for imports of corn grown from those seeds. It says Syngenta’s action led to significant damages […]