Characterization of field‐evolved resistance to pyridalyl in a near‐isogenic line of diamondback moth, Plutella xylostella.

BACKGROUND: Plutella xylostella has developed resistance to a variety of pesticides in the field. Selection, inheritance, a near‐isogenic line, cross‐resistance and biochemical mechanisms of pyridalyl resistance were characterized in a field‐collected resistant population of P. xylostella from China. RESULTS: Compared with a susceptible IVF‐S strain, the field‐collected FZ population showed ~ 350‐fold resistance to pyridalyl. The FZ‐PY strain, selected from the FZ population using pyridalyl, developed ~ 640‐fold resistance to pyridalyl. Inheritance tests indicated that pyridalyl resistance in the FZ‐PY strain was autosomal and incompletely recessive. Through successive backcrossing to IVF‐S, a near‐isogenic strain (NIL‐PY) was established that exhibited 191.21‐fold resistance to pyridalyl and no cross‐resistance to other tested popular insecticides. No significant effects of synergists and higher activities of metabolic enzymes were observed in NIL‐PY compared with IVF‐S. Furthermore, the survival rate of NIL‐PY larvae, and female oviposition, fecundity and egg viability were markedly reduced in NIL‐PY compared with IVF‐S. The fitness of NIL‐PY was found to be 0.56 compared with IVF‐S. CONCLUSION: Considering that no relevant effects of synergists or oxidative metabolism were observed in NIL‐PY, and that pyridalyl resistance results in significant fitness costs compared with IVF‐S, further research will be conducted on the mechanism of target‐site resistance. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]