A Mutation Leu1029 to His in Heliothis virescens F. hscp Sodium Channel Gene Associated with a Nerve-Insensitivity Mechanism of Resistance to Pyrethroid Insecticides

Two mutations in the Heliothis virescens F. sodium channel gene hscp are associated with pyrethroid resistance in field populations. These are valine421 to methionine (V421M) in domain I transmembrane segment S6 (IS6) and leucine 1029 to histidine (L1029H) in IIS6. L1029H was found to be common in 1995 Louisiana field collections. In order to test whether the L1029H mutation is associated with a nerve-insensitivity resistance mechanism, we designed a simplified genetic crossing and tested progenies with bioassay and electrophysiology. Individuals with the L1029H mutation displayed greater resistance to the knockdown effect of permethrin in subsequent mass-selection and family-selection experiments. Reduced sensitivity to pyrethroid was found in extracellular recordings of neuromuscular junctions and in whole-cell patch-clamp assays of dissociated single cells from the central nerverous system of the individuals carrying the L1029H mutation.