A November showdown is shaping up in California between the food industry and opponents of genetically modified organisms. Proposition 37 will let voters decide whether products containing genetically engineered crops must be labeled.

Among the leading donors to the anti-Prop 37 campaign is the Grocery Manufacturers Association, which has contributed $375,000 to oppose the measure. The association represents supermarket chains, biotech companies like Monsanto, multinational food manufacturers and fast food chains. The Council for Biotechnology Information also donated $375,000 to oppose the proposition.

In contrast, the biggest financial supporter of Prop 37 is the Organic Consumers Fund.

GMO labeling is already required in much of the world, including Europe, China and Japan. Advocates say bioengineering produces larger and more reliable crop yields. Opponents argue that the ramifications of altering plant genetics aren’t fully understood. They say consumers should be able to decide whether to eat genetically modified foods.

Genetically modified foods are common in the U.S. food supply, appearing in more than 70 percent of processed foods, according to some estimates. Corn, soybeans and cottonseed oil commonly found in supermarket products are typically genetically modified strains. And a provision in the Farm Bill making its way through Congress would make it even easier to grow biotech crops.

The California proposition, known as the Right to Know Genetically Engineered Food Act, is likely to be popular with voters. Polls show a vast majority of Californians, and Americans, support labels for GMOs. But the industry-backed anti-Prop 37 campaign is fighting back, arguing that labeling or switching to non-GMO ingredients would raise food prices. They also say the proposition would encourage lawsuits since any private citizen could sue a grocer by claiming they mislabeled a food product.

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