Ryanodine receptor mutation conferring chlorantraniliprole resistance in the eggplant fruit borer Leucinodes orbonalis Guenée (Lepidoptera: Crambidae)

Diamide resistance in field populations of Leucinodes orbonalis Guenée (Lepidoptera: Crambidae) across 10 localities of Tamil Nadu has been monitored using log dose probit mortality bioassays with chlorantraniliprole. Despite their short history of use, resistance to this insecticide has emerged in this pest. Based on LC50 values, field populations of L. orbonalis exhibited 7.35 to 268.31 fold higher resistance to chlorantraniliprole compared to the susceptible population. To investigate resistance at a molecular level, a primer was designed and examined for mutations in four sites reported earlier in other insect pests in the ryanodine receptor (RyR), which is the primary mechanism underlying diamide resistance. Sequencing results showed that only the I4775M (Isoleucine to Methionine) mutation was found in most of the field populations. Molecular docking was employed to predict the binding positions and affinity of the insecticide chlorantraniliprole with the ryanodine receptor protein, which showed a correlation between its insecticidal activity and binding values. Results from this study have direct implications for the design of appropriate resistance monitoring and management practices for sustainable control of L. orbonalis.