Transgenic Contaminants in the Traditional Seed Supply

A pilot study by the Union of Concerned Scientists found that traditional seeds of corn, soybeans, and canola sold to U.S. farmers are pervasively contaminated with low levels of DNA from genetically engineered varieties. The report warns that porous seed production systems could allow dangerous pharmaceutical or industrial transgenes to enter the food supply and argues that this contamination threatens organic agriculture, international trade, and the integrity of seed repositories.

• A pilot study of traditional corn, soybean, and canola seeds purchased from U.S. retailers revealed pervasive low-level contamination with DNA sequences from genetically engineered varieties. Combined results from two laboratories showed transgenically derived DNA in 50 percent of corn, 50 percent of soybean, and 83 percent of canola varieties tested.
• The estimated levels of transgenic contamination in the tested samples ranged from less than 0.05 percent to more than 1 percent of total genomes. While these percentages are low, they represent significant absolute quantities; for example, a 1 percent contamination rate in traditional corn seeds would equate to approximately 6,250 tons of transgenically derived seeds, filling 240 large tractor-trailer trucks.
• The report identifies a high risk that 'pharm' (pharmaceutical) and industrial crops—engineered to produce drugs, vaccines, or chemicals—could contaminate the food and feed supply through the same porous seed production and distribution systems that allowed current transgenic contamination.
• Seed contamination poses a significant threat to organic agriculture because federal standards prohibit the use of genetically engineered inputs. Organic farmers struggle to find pure seeds, and contamination can lead to eroding markets if they cannot deliver products free of transgenic DNA.
• The presence of unapproved or unwanted transgenic sequences in U.S. exports creates trade challenges, as major partners like the European Union, Japan, and South Korea have strict regulatory regimes or consumer preferences against genetically engineered crops.
• Contamination of traditional seeds may expose farmers to intellectual property risks, as they could unknowingly infringe on patents held by biotechnology companies if they plant seeds containing patented transgenic sequences.
• The report warns that transgenic sequences could surreptitiously enter new environments or wild plant populations, potentially creating 'weeds' or disrupting ecosystems, particularly if the transgenes confer a selective advantage.
• There is a risk that communal genetic storehouses and seed banks could become contaminated, undermining the long-term resilience of the food supply. The report cites a real-world example where the Charles M. Rick Tomato Genetics Resource Center at UC Davis reported contamination of its seed stock.

APA

Mellon, M., & Rissler, J. (2004). Transgenic Contaminants in the Traditional Seed Supply. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2019-09/seedreport_fullreport.pdf

Chicago

Mellon, Margaret, and Jane Rissler. Transgenic Contaminants in the Traditional Seed Supply. Union of Concerned Scientists, 2004. https://www.ucs.org/sites/default/files/2019-09/seedreport_fullreport.pdf.

Wikipedia

{{cite report |last1=Mellon |first1=Margaret |last2=Rissler |first2=Jane |title=Transgenic Contaminants in the Traditional Seed Supply |publisher=Union of Concerned Scientists |date=2004 |url=https://www.ucs.org/sites/default/files/2019-09/seedreport_fullreport.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{mellon2004transgenic, author = {Mellon, Margaret and Rissler, Jane}, title = {{Transgenic Contaminants in the Traditional Seed Supply}}, institution = {Union of Concerned Scientists}, year = {2004}, url = {https://www.ucs.org/sites/default/files/2019-09/seedreport_fullreport.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }