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Unintended Effects of Genetic Manipulation
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Conventional, certified canola seedlots were contaminated with genetically engineered seeds.

Manipulated Organism: Canola (Brassica napus).

Inserted Transgenes: Several genetically engineered (GE) canola lines have been developed with herbicide resistance traits. Resistance to the herbicide glyphosate (Roundup) has been engineered with a combination of two genes: (1) a gene from Agrobacterium strain CP4 that produces a resistant form of the EPSPS enzyme targeted by glyphosate, and (2) a modified glyphosate oxidase gene from the bacterium Ochrobactrum, which accelerates the degradation of glyphosate. Resistance to the herbicide glufosinate (Liberty) has been engineered using Streptomyces bacterial genes for the PAT enzyme, which inactivates glufosinate.

Goal of This Study: "This survey of the purity of pedigreed canola seedlots with respect to herbicide resistance traits was prompted by complaints from several farmers regarding glyphosate-resistant canola volunteers occurring unexpectedly in their fields at densities and in patterns that suggested that pollen-mediated gene flow from neighboring fields in previous years was not the source of contamination" (p. 1343).

Results of This Study:
  • Either glyphosate- or glufosinate-resistant canola plants were detected in all 16 of the conventional (non-GE), certified canola seedlots tested.

  • In 8 of the 16 seedlots, the concentration of GE seed exceeded 0.25%, which is the maximum amount of contamination allowed in certified seed.

Additional Comments: "The results of this study indicate that the pedigreed canola seed production system in western Canada is cross-contaminated with the various herbicide resistance traits at a high level and that purchasing and planting a pedigreed conventional canola seedlot does not guarantee the absence of genetically engineered traits. For those producers that grow canola and practice direct [no-till] seeding, it means that glyphosate no longer is a nonselective, broad-spectrum herbicide that can be used alone as a spring burn-off treatment" (p. 1346). Growers have been responding to this situation by using additional herbicides to achieve broad-spectrum weed control.

Source: Friesen, L. F., A. G. Nelson, and R. C. van Acker (2003). "Evidence of Contamination of Pedigreed Canola (Brassica napus) Seedlots in Western Canada with Genetically Engineered Herbicide Resistance Traits," Agronomy Journal vol. 95, pp. 1342-7.

Author Affiliations: University of Manitoba, Canada.

Funding: Not mentioned.

Product Status: Genetically engineered canola is grown on millions of acres in the US and Canada.

Copyright 2009 The Nature Institute.

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