This showed up in my mailbox yesterday via a producer's group. I
thought that the maize news group should be aware of this misleading
"PROMISCUOUS PLANTS MAY SPREAD GENES TO WEEDS
Sept. 2/98: from a University of Chicago Medical Center press release
Crops engineered to contain genes that give them resistance to pests or the
ability to produce lots of seeds, could pass these genes to their weedier
cousins producing hybrid strains of super-weeds, says Joy Bergelson,
assistant professor of ecology and evolution at the University of Chicago.
Her findings will be reported in the September 3 correspondence pages of
Nature. Artificially created plants, like wild plants, can breed with
closely related species to produce hybrids in what is called out-crossing.
For example, corn, which is a grass, can cross with timothy grass, an
abundant weed. If the corn contains a gene that confers resistance to a
pesticide, the resultant "weedy" hybrid may become a pesticide-resistant
nuisance that can compete with crops for water and nutrients. Farmers
haven't worried about outcrossing because most crop plants are
self-fertilizing, so their genes were considered unlikely to migrate to
other species. But Bergelson has demonstrated that plants thought to be
"selfing" can outcross with closely related species, and that the rate of
outcrossing appears to be enhanced by the fact that they are transgenic.
To test the frequency of outcrossing in transgenic plants, Bergelson grew
three different kinds of Arabidopsis, a selfing mustard plant, and planted
them together on a plot in central Illinois. One type contained a point
mutation in the Csr1-1 gene making it resistant to chlorsulfuron, an
herbicide. The second variety of Arabidopsis was engineered with a mutated
Csr1-1 gene, producing a transgenic chlorsulfuron-resistant plant. The
third type were wild-type Arabidopsis with normal copies of the Csr1-1
gene. The plants were left alone, and their seeds were collected at the
season's end. Plants grown from the seeds were tested for resistance to
chlorsulfuron. Resistant plants were further tested to determine if they
inherited the resistance gene from Crs1-1 mutants or from the transgenic
plants containing the implanted Csr1-1 mutant gene.
Bergelson found that twenty times as many resistant progeny received their
resistance from the transgenic plants as from the mutant plants. "It is
unclear why the transgenic plants had such an abnormally high incidence of
out crossing," says Bergelson, "but the results demonstrate that genetic
engineering can substantially increase the incidence of outcrossing in a
She warns that the widespread use of transgenic crops may directly cause
the creation of weeds with traits intended to increase the fitness of
crops, spurring a need for new pesticides."
Elizabeth A. Lee
Plant Agriculture Dept.
Crop Sci. Bldg.
University of Guleph
Guelph, ON N1G 2W1 Canada
(519)824-4120 extension 3360
elee at plant.uoguelph.ca