Bt-resistance costs pink bollworms

Insect populations that have evolved resistance to Bt toxins have an increased susceptibility to other insecticidal toxins, researchers from a group of US universities have found. They studied the fitness costs to pink bollworms ( Pectinophora gossypiella) of resistance to the Bt Cry1Ac toxin, which is expressed in several genetically modified varieties of cotton, maize and soybeans. Resistance is conferred by a recessive mutation in cadherin protein coding genes expressed in larval midguts. Resistant larvae produce a truncated version of the cadherin protein that cannot bind to the Bt toxin, preventing its absorbtion.