Genetic analysis of non-recessive factors of resistance to diazinon in the SKA strain of the housefly (Musca domestica L.).

The recent allocation of many visible mutants to specific linkage-groups has made possible their use as genetic markers in the study of the inheritance of insecticide resistance. In most organophosphorus-resistant strains, resistance is controlled by a single gene on the V linkage-group responsible for resistance and low ali-esterase activity, but in some strains more than one factor is present. The present work was done to analyse the genetics of resistance to diazinon in a strain (the SKA strain) bred from two diazinon-resistant strains. Crosses between the SKA flies and four susceptible recessive marker strains, each marked on one linkage-group, followed by test-crosses with recessive markers and by bioassays of each cross, have shown that non-recessive factors for resistance to diazinon are present on the IV and V linkage-groups. The SKA strain genetically resembles its parents but differs by being considerably more resistant.