Genetics and mechanisms of permethrin resistance in the YPER strain of house fly

A strain of house fly was collected from the Third Yumenoshima Island in Japan and selected with the pyrethroid insecticide permethrin. Resistance to permethrin evolved to >18; 400-fold in the selected (YPER) strain, and the mechanisms and genetics of resistance in this strain were examined. Permethrin resistance was decreased by pretreatment with piperonyl butoxide or 2-propynyl 2,3,6-trichlorophenyl ether, but not S,S,S-tributylphosphorotrithioate or diethylmaleate. The level of total cytochromes P450 was 2.7-fold increased, and the level of cytochrome b5 was 1.5-fold increased, in YPER compared to the susceptible CS strain. These results suggest P450 monooxygenases, but not hydrolases or glutathione Stransferase, are a mechanism of resistance in the YPER strain. Analysis of the para-homologous sodium channel a-subunit gene in YPER indicates this strain has the super-kdr allele. Permethrin resistance in the YPER strain was inherited as a multigenic and incompletely recessive trait. A factorial analysis of resistance in the YPER strain indicated the relative contribution to resistance by the different autosomes was 2 > 3 > 5P 1. Comparison of YPER with three other strains of house fly having high levels of permethrin resistance (LPR, NG98, and ALHF) indicates the genetic basis of this trait is variable between populations. This indicates there may be a greater difficulty for the development of diagnostic tools that could be used reliably over large areas to monitor pyrethroid resistance in house flies than was previously thought. 2002 Elsevier Science (USA). All rights reserved.