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In Context #11 (Spring, 2004, p.5); copyright 2004 by The Nature Institute

Widespread GM Contamination of Seed Supply

This past February the Union of Concerned Scientists (UCS) published a study demonstrating that DNA from genetically engineered crops is contaminating the American supply of conventional, non-engineered seeds.* UCS staff bought 50 pound bags of conventional soybean, corn, and canola seeds from seed retailers. They purchased six different varieties of each species, "representing a substantial portion of the 2002 traditional seed supply for these three crops" (p. 28). They then sent batches of these seeds to two different testing labs to determine whether there is any foreign DNA from genetically modified crops in the seeds.

The testers ground up thousands of seeds and then took a sample of the ground material, which they tested for the foreign genes using the PCR (Polymerase Chain Reaction) method. At one lab foreign DNA sequences were detected in three of the six varieties of soybeans and corn (50 percent) and in all the varieties of canola (100 percent). In the other lab, foreign DNA was found in five of six varieties of all three crops (83 percent). The foreign DNA came both from herbicide-resistant GM plants as well as insecticide-producing GM plants and included DNA from varieties sold by the biotech companies Monsanto, Syngenta, and Bayer.

The other question the study addresses is the degree of contamination. Knowing that 50 to 100 percent of the seed batches are contaminated is not the same thing as knowing the level of contamination within the batches. The contamination level ranged from 0.05 percent to over one percent of the DNA. (European Union regulations allow one percent contamination of organic crops by genetically modified DNA; above this level farmers can no longer call their crops "organic.") The scientists estimate that if one percent of the conventional seed supply of corn in 2002 was contaminated by genetically modified seed, the contaminated seed would fill 240 large tractor trailers (or 250,000 50-pound bags).

How did this widespread contamination occur? The study did not attempt to answer this question. GM seeds could have mixed with conventional varieties anywhere in the process of seed planting, harvesting, processing, storing, transporting, or packaging. Or pollen from GM plants could have pollinated non-GM crops, creating hybrids that contain the foreign DNA. Since soybeans are mainly self-pollinators, it is likely that their contamination is due to seed mixing.

Whatever the pathway, an astoundingly broad contamination of the seed supply has occurred without notice over the past years. (The first commercial GM soybeans, corn, and canola were planted in 1996.) Farmers buying conventional seeds of these three crops cannot at all be sure that their seeds are GM-free. Any illusion that GM crops and seeds are being kept separate from conventional (and organic) crops and seeds is clearly dispelled by this study. CH

(* The study referred to above is entitled Gone To Seed: Transgenic Contaminants in the Traditional Seed Supply, by Margaret Mellon and Jane Rissler. Cambridge, MA: Union of Concerned Scientists, 2004.)

Original source: In Context #11 (Spring, 2004, p.5); copyright 2004 by The Nature Institute

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