ABSTRACT
This chapter describes a complementary laboratory program investigating aspects of the genetics of the resistance. The main objectives of this genetic analysis were to determine whether the Pyrethroid insecticides resistance (SP-R) showed maternal effects, was dominant, was single gene or polygenic, and was inherited in the same way in both strains of SP-R Typhlodromus pyri. In these three cases, the inheritance of insect resistance to synthetic pyrethroids was being investigated and in all three, lower than expected mortalities occurred in the backcross. All rearing and crossing experiments were carried out in the laboratory on acrylic plates, and numbers were sometimes inadequate to give good fitting concentration/mortality curves. Concentration/mortality curves were derived for the parental strains and the progeny of the crosses. Selective breeding programs have produced SP-R in other phytoseiid mites. Thus, both SP-resistant strains of T. pyri exhibit incomplete dominance for SP resistance.
