Inheritance of Resistance to Fenitrothion and Pirimiphos-methyl in the Rice Stem Borer, Chilo suppressalis (Lepidoptera: Pyralidae)

The inheritance of fenitrothion resistance (22-fold) and pirimiphos-methyl resistance (500-fold) was studied in the OP-resistant Hata-f strain of the rice stem borer, Chilo suppressalis. The resistance was found to be incompletely recessive, and no extranuclear effects were found. The degree of dominance (D) for fenitrothion was —0.31 to —0.37 and that for pirimiphos-methyl was —0.14 to —0.21. Observed mortalities for the backcross progenies [formula omitted] were almost identical with the expected on the basis of a single major gene inheritance. However, the observed mortalities at high dosages were significantly higher than expected, indicating that minor modifying genes might be involved in the resistance. The inheritance of the two fenitroxon detoxication activities (binding protein and hydrolysis) were also incompletely recessive.