A comparative genetical study on DDT resistance in adults and larvae of the mosquito Aedes aegypti L

Abstract

Inheritance of DDT resistance has been studied in crosses between the highly resistant ‘T’ strain of A. aegypti (constituted by inbreeding from the TRINIDAD DDT-resistant stock) and the ‘64’ susceptible strain.Larval DDT resistance derives from a major gene R^DDT1 on linkage group II, the order being R^DDT1–s–y. Linkage group III may also contribute to larval resistance. Linkage group I makes no contribution.Adult DDT resistance derives from a major gene R^DDT2, 18·2 ± 2·1 units from the market blt on linkage group III. Linkage group II has no influence on adult resistance.Selection with DDT to retain only R^DDT1/+ segregants in larvae of backcrosses R^DDT1/+×+/+ did not increase resistance in resulting adults, confirming the difference in genetic mechanism at the two stages.The F₁ progenies from reciprocal crosses between ‘T’ and ‘64’ differed slightly but significantly in larval resistance, modifying the influence of the major gene R^DDT1 in the heterozygote.The early developmental stages of the R^DDT1/+ phenotype (up to the fourth larval stage) were more viable than the +/+ phenotype in backcross segregation. The difference in mortality probably exceeded 30%.