What could be worse for farmers and gardeners than weeds? Superweeds!

Many opponents of genetically modified crops are afraid that highly invasive weeds might result when the plants cross breed with wild weeds. However, an international team of researchers led by University of Tennessee (UT) plant scientists says the fears are overblown.

In one of the first studies* in which weeds have been genetically modified by hybridization with a crop and tested under agricultural field conditions, superweeds were not created.

Quite the contrary says UT plant geneticist Neal Stewart. “Our results challenge some preconceived notions about the consequences of gene flow,” he said. “The study indicates that it might take more than transgenes to make weedier weeds.”

The research team conducted both laboratory and field experiments, and the results of their work are published in the September issue of the journal Molecular Ecology.

Stewart says canola plants containing a Bt insect resistance transgene and a marker gene were hybridized multiple times with a related weed, field mustard, also known as wild turnip.

“In no case was the modified weed more competitive, and in some cases it was less so,” Stewart said. “Even though the modified weeds were protected from insect damage they were less weedy when compared with wild type weeds in wheat fields.”

The research team included members from the Southeastern United States, Canada and the United Kingdom. Stewart was the principal investigator for two USDA grants that supported the research. Support was also supplied by the Biotechnology and Biological Sciences Research Council (BBSRC), the United Kingdom’s lead funding agency for academic research and training in the non-clinical life sciences.

Field trials were conducted at agricultural experiment stations in Tennessee, Georgia, and North Carolina.

*Growth, productivity, and competitiveness of introgressed weedy Brassica rapa hybrids selected for the presence of Bt cry1Ac and gfp transgenes
Halfhill, M.D., H.S. Moon, J.P Sutherland, G.M Poppy, S.I Warwick, T.W. Rufty, A.K. Weissinger, P.L. Raymer, and C.N. Stewart, Jr. 2005.
Molecular Ecology
Volume 14 Issue 10 Page 3177 - September 2005