Costs of transgenic herbicide resistance introgressed from Brassica napus into weedy B. rapa

Authors

  • ALLISON A. Snow,

    1. Plant Biology and Biogeochemistry Department, PBK-301, Risø National Laboratory, DK-4000 Roskilde, Denmark, ,
    2. Department of Plant Biology, Ohio State University 1735 Neil Avenue, Columbus, OH, 43210, USA
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  • BENTE Andersen,

    1. Plant Biology and Biogeochemistry Department, PBK-301, Risø National Laboratory, DK-4000 Roskilde, Denmark, ,
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  • RIKKE BAGGER Jørgensen

    1. Plant Biology and Biogeochemistry Department, PBK-301, Risø National Laboratory, DK-4000 Roskilde, Denmark, ,
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  • The authors are investigating gene flow, introgression, and the ecological consequences of escaped transgenes in several crop–weed systems in Europe and the USA. This research was carried out while Allison Snow was on a sabbatical leave from Ohio State University, where she is an associate professor. Rikke Bagger Jørgensen is a senior scientist and Bente Andersen is a staff researcher at Risø National Laboratory.

A. A. Snow

Abstract

Wild relatives of genetically engineered crops can acquire transgenic traits such as herbicide resistance via spontaneous crop–wild hybridization. In agricultural weeds, resistance to herbicides is often a beneficial trait, but little is known about possible costs that could affect the persistence of this trait when herbicides are not used. We tested for costs associated with transgenic resistance to glufosinate when introgressed into weedy Brassica rapa. Crosses were made between transgenic B. napus and wild B. rapa from Denmark. F1 progeny were backcrossed to B. rapa and BC1 plants were selected for chromosome numbers similar to B. rapa. Further backcrossing resulted in a BC2 generation that was hemizygous for herbicide resistance. We quantified the reproductive success of 457 BC3 progeny representing six full-sib families raised in growth rooms (plants were pollinated by captive bumblebees). Pollen fertility and seed production of BC3 plants were as great as those of B. rapa raised in the same growth rooms. Segregation for herbicide resistance in BC3 plants was 1:1 overall, but the frequency of resistant progeny was lower than expected in one family and higher than expected in another. There were no significant differences between transgenic and nontransgenic plants in survival or the number of seeds per plant, indicating that costs associated with the transgene are probably negligible. Results from this growth-chamber study suggest that transgenic resistance to glufosinate is capable of introgressing into populations of B. rapa and persisting, even in the absence of selection due to herbicide application.

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