A genetic analysis of cyromazine resistance in Drosophila melanogaster (Diptera : Drosophilidae)

Flies resistant to the insect growth regulator cyromazine were selected in the F-1 generation from a cyromazine-susceptible strain of Drosophila melan ogaster (Meigen) treated with ethyl methanesulfonate. Four resistant strain s were isolated by screening with cyromazine at a concentration >LC100 of s usceptibles. In each strain, resistance is conferred by a single gene mutat ion. Cyromazine resistance in two of the mutants (rst(1a)cyr(1) and rst(1a) cyr(2)) localizes to map position 17 of the X chromosome. Evidence is prese nted that these mutations are alleles of the gene rst(1a)cyr. Cyromazine re sistance in another of the mutants (Rst(1b)Cyr) is also X-linked, and local izes to map position 49 of the X chromosome. The location of the gene confe rring cyromazine resistance in the other mutant (Rst(2b)Cyr) is map positio n 66 of chromosome II. This is possibly an allele of a previously character ized cyromazine resistance gene, Rst(2)Cyr. Dosage-mortality analyses demon strate a low level of cyromazine resistance is conferred in all strains.