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Unintended Effects of Genetic Manipulation
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Herbicide-resistant canola volunteers were still detected after ten years of stringent control.

Manipulated Organism: Canola (Brassica napus).

Inserted Transgenes: Resistance to the herbicide glufosinate (Liberty, Basta) has been engineered using a Streptomyces bacterial gene for the PAT enzyme, which inactivates glufosinate. Male sterility (barnase) and restorer (barstar) genes from the bacterium Bacillus amyloliquefaciens have also been inserted for control of seed production.

Goal of This Study: "Coexistence between genetically modified (GM) and non-GM plants is a field of rapid development and considerable controversy. In crops, it is increasingly important to understand and predict the GM volunteer emergence in subsequent non-GM crops" (p. 314). In 1995 a field trial was conducted on university farmland involving both glufosinate-resistant and conventional varieties of canola. From 1996 to 2005, no glufosinate-resistant canola was planted on the farm, and canola volunteers were controlled with herbicides before flowering.

Results of This Study:
  • In 2005, ten years after the field trial, 38 volunteer canola plants were found in the 100 ft. by 130 ft. test plot. Of these plants, 15 survived when sprayed with glufosinate. Molecular genetic analysis of the glufosinate-resistant canola volunteers confirmed the presence of transgenes.

  • Because canola volunteers were strictly controlled from 1996 to 2005, the authors conclude that "the GM volunteers collected in 2005 most probably were recruited from 10-year old seeds" (p. 316).
Additional Comments: There is no reason to think that the long-term persistence of canola observed in this study was because of genetic engineering. In any field planted to canola, volunteers can be expected to contaminate future crops. The point is that seed longevity may limit the possibility of growing a pure, non-GM canola crop for many years following a GM canola crop.

Source: D'Hertefeldt, T., R. B. Jorgensen, and L. B. Pettersson (2008). "Long-term Persistence of GM Oilseed Rape in the Seedbank," Biology Letters vol. 4, pp. 314-17.

Author Affiliations: Lund University, Sweden; Technical University of Denmark.

Funding: Swedish Research Council; K&A Wallenberg Foundation; EU project SIGMEA.

Product Status: Glufosinate-resistant canola is commercially grown around the world.

Copyright 2009 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/canola_005.php

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