Farmers worldwide boosted their plantings of genetically modified crops by 13 percent last year despite European resistance. U.S. farmers continue to be the dominant users of biotech crops, having planted 135 million of the 252 million acres seeded to gene-altered varieties worldwide in 2006, according to a survey by the International Service for Acquisition of Agri-biotech Applications, an organization that tracks the industry.

Farmers say biotech seeds, which are produced through genetic engineering rather than conventional breeding techniques, reduce the use of crop protection products and increase crop yields.

In the U.S., biotech plantings grew by 12 million acres last year, accounting for more than one-third of the global increase of 30 million acres.