Snow said that even when the unaltered weeds were given the advantage of an ideal growing environment, they didn't on average produce more fruits or seeds than the hybrid weeds.
The researchers crossed the hybrid plants with unaltered weeds, and saw that the gene for herbicide resistance persisted in about half of the weed population, as expected from Mendel's laws of inheritance. What did change was the hybrid weeds' appearance.
"By the third generation, the weeds that carried the gene for herbicide resistance looked exactly like normal weeds. The only way to tell them apart was to expose them to herbicide or test their DNA," said Snow.
She added that the only way a farmer would be able to tell the difference would be to spray all the weeds with herbicide and see which ones survive -- but that would just give the herbicide-resistant weeds more room to grow.
Cultivated crop plants are generally less hearty than weeds -- they don't produce as many branches or seeds, and they're more vulnerable to bad weather, pests, and poor soil. That's why scientists hoped that crop/weed hybrids wouldn't be able to compete with their heartier pure-weed relatives. This latest study shows that hybrid weeds may carry the beneficial transgene of the crop parent and still hang on to the aggressiveness of the weed parent.
These studies picked up speed when transgenic, herbicide-resistant oilseed rape hit the commercial U.S. market in 1993. Since then, oilseed rape production has been on the rise. In 1997, American farmers produced six times more canola oil than they did just five years before, according to the United States Department of Agriculture. That year, the U.S. produced over $100 million worth of canola -- a popular cooking oil these days because it contains the lowest amount of saturated fat of any food oil.
Manufacturers use canola as an ingredient in soap, margarine, and l
'"/>
Contact: Allison Snow
Snow.1@osu.edu
(614) 292-8433
Ohio State University
6-Aug-1998