TIGHT GENETIC-LINKAGE BETWEEN THE KDR INSECTICIDE RESISTANCE TRAIT AND A VOLTAGE-SENSITIVE SODIUM-CHANNEL GENE IN THE HOUSE-FLY

The kdr insecticide resistance trait in the house fly, Musca domestica , confers resistance to the rapid paralysis (knockdown) and lethal eff ects of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and pyreth roids. Flies with the kdr trait exhibit reduced neuronal sensitivity t o these compounds. which are known to act at voltage-sensitive sodium channels of nerve membranes. To test the hypothesis that a mutation in a voltage-sensitive sodium channel gene confers the kdr phenotype, we have cloned genomic DNA corresponding to a segment of the house fly h omologue of the para sodium channel gene of Drosophila melanogaster, i dentified restriction-site polymorphisms within this segment between t he kdr strain 538ge and an inbred insecticide-susceptible lab stain, a nd developed a sensitive polymerase chain reaction-based diagnostic pr ocedure to determine the sodium channel genotype of individual flies. A genetic linkage analysis performed with these molecular markers show s that the kdr trait is tightly linked (within about 1 map unit) to th e voltage-sensitive sodium channel gene segment exhibiting the DNA seq uence polymorphism. These findings provide genetic evidence for a muta tion at or near a voltage-sensitive sodium channel gene as the basis f or kdr resistance.