Inheritance of resistance and fitness cost parameters to cyantraniliprole in the resistant and susceptible strains of Plutella xylostella L.

The diamondback moth (Plutella xylostella L.) is a major pest of cruciferous crops, causing significant yield losses worldwide. Its remarkable ability to develop resistance to over 100 insecticides has made it one of the most resilient agricultural pests. Cyantraniliprole, a diamide insecticide targeting ryanodine receptors, was selected for this study due to its novel mode of action and its efficacy against resistant populations. This laboratory study investigated the inheritance pattern and fitness costs associated with cyantraniliprole resistance in P. xylostella. F₂₅S larvae (larvae from the 25th generation of lab reared susceptible DBM) were subjected to increasing median lethal (LC₇₀) concentrations of cyantraniliprole (0.285 to 9.453 mg ml⁻¹) for 15 generations up to F₄₀ generations under continuous selection pressure. Bioassays determined median and post median lethal concentrations (LC₅₀ and LC₇₀), resistance ratios, realized heritability (h² = 0.386), and response quotient (Q = 0.515), indicating substantial genetic variability and rapid resistance evolution. Genetic crosses showed resistance to be autosomal, incompletely recessive, and influenced by maternal effects. Resistant populations exhibited significant fitness costs, including reduced egg hatchability (80% in resistant and 95% in susceptible), lower larval and pupal weight, higher malformed adult emergence and low net reproductive rate (15 and 45 individuals/female in resistant and susceptible respectively). These findings provide critical insights into resistance dynamics and underscore the need for resistance management strategies, such as rotating insecticides with different modes of action, to sustain the effectiveness of cyantraniliprole in managing this economically important pest.