Genetics of pyrethroid resistance in a strain (ALHF) of house flies (Diptera : Muscidae)

Five house fly lines were derived from crosses of the pyrethroid-resistant ALHF (wildtype) and the susceptible aabys (bearing recessive morphological markers on each of five autosomes) strains. Each line was homozygous for on e mutant-type marker from aabys. The level of resistance to permethrin was measured for each line to determine the genetic linkage of pyrethroid resis tance in ALHF. Permethrin resistance in ALHF was 6600-fold compared with th at in aabys. Resistance in flies bearing a mutant-type marker on autosome 4 was similar to that in ALHF. Flies with mutant-type markers on autosomes I and 2 had relatively lower resistance than ALHF flies with mutant-type mar kers on autosomes 3 and 5 had much lower levels of resistance. These result s demonstrated that factors on autosomes 3 and 5 play very important roles in pyrethroid resistance, whereas factors on autosomes I and 2 may have rel atively small roles in resistance. Piperonyl butoxide (PBO) increased toxic ity of permethrin in strains with mutant-type markers on autosomes 3 and 4 similar to that in ALHF Slightly decreased synergism ratios in strains with autosomes I and 2 mutant-type markers compared with ALHF indicated that fa ctors on autosomes I and 2 might make a small contribution in P450 monooxyg enase-mediated resistance. However, when the autosome 5 mutant-type marker was present, PBO did not substantially decrease resistance, suggesting that the factor(s) on autosome 5 plays the most important role in P450 monooxyg enase-mediated resistance. The resistance ratios of permethrin + PBO in str ains with mutant-type markers on autosomes 1, 2, and 5 were significantly l ower than those in ALHF suggesting that factors on autosomes 1, 2, and 5 mi ght be involved in pyrethroid resistance mechanisms other than P450-mediate d detoxication. Injection did not change levels of resistance in the house flies tested. revealing that decreased rate of cuticular penetration (pen) probably does not play an important role in pyrethroid resistance in ALHF. The interaction and regulation of different mechanisms and/or factors invol ved in pyrethroid resistance in house flies are discussed. (C) 2001 Academi c Press.