Novel mutations in the para-homologous sodium channel gene associated with phenotypic expression of nerve insensitivity resistance to pyrethroids in Heliothine lepidoptera

Coding sequences from the intracellular segment linking repeat domains III and IV of the para-homologous sodium channel gene were amplified and cloned from two species of Heliothine larvae using RT-PCR techniques. Sequence comparisons between standard laboratory susceptible and nerve insensitive strains of the tobacco budworm (Heliothis virescens) and the cotton bollworm (Helicoverpa armigera) identified two mutations. These were an aspartic acid (G (A) under bar C) to valine (G (T) under bar C) and a glutamic acid (G (A) under bar A) to glycine (G (G) under bar A) mutation, PCR and sequencing was undertaken only on individuals that were demonstrated to be phenotypically nerve insensitive or susceptible to pyrethroids using a neurophysiological technique. The finding of identical mutations across two species suggests that they may be implicated in resistance.