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Can transgenic crops create super weeds?

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November 20, 1996 - An article in the October 11, 1996 issue of Science reported the opinions of an assortment of scientists on the potential for genes moving from transgenic crops to wild plants, therefore creating a "superweed". As might be expected, there were a wide range of views on this topic. The article reported results of two studies that documented unusually high rates of gene flow between cultivated varieties of sunflower and stawberry into wild types of the two species. In sunflower, marker genes were found at a frequency of 28% in wild sunflower growing near fields where sunflower had been grown as a crop for 10 years, whereas the frequency was 38% after 35 years. An ecologist from Clemson University reported that 50% of the wild strawberries growing within 150 feet of a strawberry field contained marker genes from the cultivated strawberries. This relatively high rate of gene flow between cultivated and wild biotypes has raised the concern that genes from transgenic crops could move into wild plants, thereby creating a superweed. Researchers in Denmark found than the same movement can happen with genes from transgenic crops. They reported that a transgenic herbicide resistance gene moved from oilseed rape to its weedy relative, field mustard (Brassica campestris).

Source: Science, Oct. 11, 1996. Vol. 274:180-181.

Prepared by Bob Hartzler, extension weed management specialist, Department of Agronomy, Iowa State University

For more information contact:
ISU Extension Agronomy
2104 Agronomy Hall
Ames, Iowa 50011-1010
Voice: (515) 294-1923
Fax: (515) 294-9985
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Common chemical and trade names are used in this publication. The use of trade names is for clarity by the reader. Inclusion of a trade name does not imply endorsement of that particular brand of herbicide and exclusion does not imply nonapproval.