Experimental cross-pollination between transgenic herbicide-resistant
canola and wild field mustard led to highly fertile, herbicide-resistant
wild field mustard.
Manipulated Organism:
Canola (Brassica napus ssp. Oleifera), otherwise known as
oilseed rape.
Inserted Transgenes and Target Effect:
Bar gene from the bacterium Streptomyces to make canola
resistant to the bleaching herbicide glufosinate. Glufosinate is the
active ingredient in the herbicides Basta, Buster, Radicale, etc. In this
study the researchers used a transgenic line of Drakkar oilseed rape,
serial number 93B1104, developed by Plant Genetic Systems, Belgium.
Goal of This Study:
Investigate the likelihood that naturally occurring cross-pollination
between transgenic canola and field mustard (Brassica rapa)
might create viable field mustard populations that are also resistant
to the herbicide. The researchers cross-pollinated transgenic
glufosinate-resistant canola with its weedy relative, field mustard.
Results of This Study:
Glufosinate-resistant field mustard plants arose through crossing with
glufosinate-resistant canola. The field mustard plants were as fertile and
produced as many seeds as unmanipulated field mustard grown in the same
growth rooms: "There were no significant differences between transgenic
and nontransgenic plants in survival or the number of seeds per plant"
(p. 605). In other words, the fact that the field mustard plants had
incorporated and expressed the gene construct for glufosinate-resistance
did not reduce their survival fitness.
Additional Comments:
Cross-pollination between canola and field mustard is not an infrequent
occurrence. When field mustard grew within a canola field, and, in
addition both weed and crop flowered at the same time, up to 69% of the
field mustard seeds were found to be hybrid seeds. The researchers of
the study conclude: "Our results support the widespread assumption that
once a transgenic trait such as glufosinate resistance has been selected
for marketing, it is not likely to entail a strong fitness disadvantage
when transferred to weedy B. rapa populations. . . . Also, there is
some practical urgency for knowing more about this particular weed-crop
complex because B.rapa is already a serious weed of more than 20
crops in over 50 countries . . . and glufosinate-resistant oilseed rape is now
being grown commercially. If further field experiments also demonstrate
little or no costs associated with transgenic resistance to glufosinate,
it is possible that the spread of this transgene to natural populations
of B. rapa will lead to infestations that are more difficult to
control" (p. 613).
Source:
Snow, A. A., B. Andersen, and R. Bagger Jørgensen (1999). "Costs of
Transgenic Herbicide Resistance Introgressed from Brassica napus
into Weedy B. rapa," Molecular Ecology vol. 8, pp. 605-15.
Author Affiliations:
Risø National Laboratory, Denmark; Ohio State University.
Funding:
Danish Nature and Forestry Agency; Novo Nordisk Foundation; Department
of Plant Biology and Biogeochemistry, Risø National Laboratory;
Danish National Bank.
Product Status:
Transgenic glufosinate-resistant canola varieties are grown commercially
in Canada and the U.S.A.
Copyright 2008 The Nature
Institute.
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