By Daniel Stolte, University Communications, June 19, 2012
Pests are adapting to genetically modified crops in unexpected ways, researchers have discovered. The findings underscore the importance of closely monitoring and countering pest resistance to biotech crops.
Resistance of cotton bollworm to insect-killing cotton plants involves more diverse genetic changes than expected, an international research team reports in the journal Proceedings of the National Academy of Sciences.
To decrease sprays of broad-spectrum insecticides, which can harm animals other than the target pests, cotton and corn have been genetically engineered to produce toxins derived from the bacterium Bacillus thuringiensis, or Bt.
A major surprise came when the team identified two unrelated, dominant mutations in the field populations. "Dominant" means that one copy of the genetic variant is enough to confer resistance to Bt toxin. In contrast, resistance mutations characterized before from lab selection are recessive – meaning it takes two copies of the mutation, one provided by each parent, to make an insect resistant to Bt toxin.
"Dominant resistance is more difficult to manage and cannot be readily slowed with refuges, which are especially useful when resistance is recessive," Tabashnik said.