Inheritance of insecticides tolerance in resistant colonies of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae)

Resistant (R) strains of the egg parasitoid Trichogramma chilonis Ishii were developed against the three new insecticides viz., indoxacarb, spinosad and tebufenozide through 40 cycles of selection in the laboratory selection pressures. The resistant factor observed was 8.7, 4.8 and 2.4 folds in resistant strain over susceptible strain of T. chilonis for indoxacarb, spinosad and tebufenozide, respectively. Mode of inheritance of insecticides tolerance studied using respective resistant ‘R’ and susceptible ‘S’ strains of T. chilonis. The degree of dominance (D) of indoxacarb tolerance was incomplete recessive for tolerant females and semi dominant for tolerant males. For spinosad, dominance levels were semi dominant for resistant females and incomplete recessive for resistant males. For tebufenozide, resistance was governed by semi dominant gene for resistant females and incomplete recessive gene for resistant males. The backcrossing of F₁ progeny with tolerant parent indicated that strong resistance gene was coded by the coordination of genes already present in indoxacarb male genotype, for both spinosad and tebufenozide R female.