Biologists at the University of California, San Diego have discovered the genetic and molecular means by which roundworms, and probably insects, can develop resistance to the most widely used biologically produced insecticidecrystalline toxins from the bacterium Bacillus thuringiensis, or Bt.Such Bt toxins, which are safe to humans and other vertebrates and far more environmentally friendly than pesticides, have been sprayed on crops by organic farmers for decades. They have also played an important role in Africa in controlling insects that carry disease and are now being used in genetically modified corn, cotton and other crops to control caterpillars and beetles. But as the use of Bt toxins expands worldwide, scientists fear their long-term effectiveness will be threatened by the development of Bt-resistant strains.The achievement by the UCSD biologists, reported in the August 3 issue of Science, provides important molecular and genetic information that will help scientists develop strategies to delay or circumvent the evolution of Bt-resistant strains of roundworms and insects.
"There are insects in the wild now that contain gene variants that allow them to be resistant to Bt toxins, but fortunately they are small in number," says Raffi V. Aroian, an assistant professor of biology at UCSD who headed the study. "However, as more crops with Bt genes are planted, its only a matter of time before populations of Bt-resistant insects grow numerous enough to become economically troublesome to farmers hoping to control these insects."
their study, the researchers examined mutant genes they discovered in the
roundworm C. elegans that confer resistance to a particular Bt toxin known as
Cry5B. Joel S. Griffitts, a graduate student at UCSD and the lead author of
the study, cloned one of these five mutant genes, which the scientists n
Contact: Kim McDonald
University of California - San Diego