Genetic Basis of a Specific Resistance to Malathion in the Australian Sheep Blow Fly, Lucilia cuprina (Diptera: Calliphoridae)

Abstract

Specific resistance to the organophosphorus insecticide malathion in the RM strain of the Australian sheep blow fly, Lucilta cuprina (Wiedemann), is controlled by an incompletely dominant gene on chromosome 4. This gene, RMAL, was shown to be 24.5 ± 1.3 map units from the visible marker gene sv. The major gene for resistance to diazinon and other organophosphorus insecticides, ROP-1, was mapped at 21.8 ± 1.3 units from sv. It was not possible to separate the locations of RMAL and Rop-1 in the mapping experiments. However, an allelism test showed that the two genes were closely linked but independent of each other on chromosome 4. Malathion-specific resistance was also shown to be associated with high esterase activity. No significant recombination could be detected between RMAL and a single locus controlling high esterase activity, suggesting that malathion resistance is derived from enhanced esteratic metabolism of the insecticide.