Herbicide-resistant canola volunteers were still detected after ten years of
Canola (Brassica napus).
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
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:
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.
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
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).
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.
Lund University, Sweden; Technical University of Denmark.
Swedish Research Council; K&A Wallenberg Foundation; EU project SIGMEA.
Glufosinate-resistant canola is commercially grown around the world.
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