Cyromazine resistance in Drosophila melanogaster (Diptera: Drosophilidae) generated by ethyl methanesulfonate mutagenesis.

Flies resistant to cyromazine (CGA-72662) were selected in susceptible laboratory populations of Drosophila melanogaster (Meigen) treated with ethyl methane-sulfonate after growth on cyromazine concentrations > LC99. Two resistant lines were obtained. In each case, resistance was a result of a mutation in a single, but different, gene. The resistance genes, designated Rst(2)Cyr and Rst(3)Cyr, were localized to map positions 64 on chromosome II and 47 on chromosome III, respectively. Concentration-mortality analysis of each mutant revealed that both genes conferred a low level (< 5 times) of resistance to cyromazine. Rst(2)Cyr produced LC99s of 1.3 x 10(-4)% (wt/vol) for heterozygotes and 2.7 x 10(-4)% for homozygotes; Rst(3)Cyr values were 1.6 x 10(-4) and 1.8 x 10(-4)%, respectively. These values compare with an LC99 of 5 x 10(-5)% for wild-type. The role of D. melanogaster as a model for insecticide resistance studies is discussed, especially the comparison of laboratory-generated cyromazine resistance in D. melanogaster with field resistance in Musca domestica L.