THE KNOCKDOWN RESISTANCE (KDR) MUTATION IN PYRETHROID-RESISTANT GERMAN COCKROACHES

A point mutation in the para-homologous sodium channel gene has been s hown to be associated with knockdown resistance (kdr) in several insec t species including the German cockroach. In this study, we analyzed t he genomic organization of the region where the kdr mutation resides a nd then performed polymerase chain reaction (PCR) and sequencing using genomic DNA as the template to detect kdr mutation in 24 pyrethroid-r esistant German cockroach strains, most of which have been collected r ecently from the field. The kdr mutation, G to C at nt 2979 resulting in a leucine to phenylalanine amino acid substitution, was detected in 20 strains including 2 strains from overseas (China and Germany). Our results clearly indicate that the kdr mutation is widespread in Germa n cockroach populations. However, the super-kdr mutation detected in s uper-kdr house flies was not found in any of the 4 strains that showed higher levels of knockdown resistance. Little correlation was observe d between the presence of the kdr mutation and the level of knockdown resistance, suggesting the existence of multiple resistance mechanisms in many of these strains, (C) 1998 Academic Press.