PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 60, 195–204 (1998) ARTICLE NO. PB982339 The Knockdown Resistance (kdr) Mutation in Pyrethroid-Resistant

A point mutation in the para-homologous sodium channel gene has been shown to be associated with knockdown resistance (kdr) in several insect species including the German cockroach. In this study, we analyzed the genomic organization of the region where the kdr mutation resides and then performed polymer-ase chain reaction (PCR) and sequencing using genomic DNA as the template to detect kdr mutation in 24 pyrethroid-resistant German cockroach strains, most of which have been collected recently 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 German cockroach populations. However, the super-kdr mutation detected in super-kdr house flies was not found in any of the 4 strains that showed higher levels of knockdown resistance. Little correlation was observed 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. q1998 Academic Press INTRODUCTION cross-resistance to the entire class of pyrethroids as well as DDT. VPIDLS was the first German The German cockroach is an important house