By the third generation, the weeds that carried the gene for herbicide resistance looked exactly like normal weeds. 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 a handful of years before, according to the United States Department of Agriculture.
Manufacturers use canola as an ingredient in soap, margarine, and lamp fuel.
A refined version of the oil is used as a lubricant. The seed residue after oil extraction provides animal feed. This isn't a problem for corn, soybeans, potatoes, and tomatoes, none of which have weedy relatives in the U.S. Sunflower and squash plants, on the other hand, are both native born, so they naturally have genetically-compatible weeds growing nearby. That's why genes from cultivated oilseed rape, sunflowers, and squash can escape from crop plants into the weed population. In fact, previous studies have shown that oilseed rape pollen can reach weeds nearly one mile away.