Cross‐resistance, fitness costs, and biochemical mechanism of laboratory‐selected resistance to tenvermectin A in Plutella xylostella

Abstract

BACKGROUND Tenvermectin A is a new avermectin derivative that has good insecticidal and acaricidal effects. In order to study the resistance of Plutella xylostella to tenvermectin A, a sensitive strain (SS) and a laboratory‐selected tenvermectin A‐resistant strain (RS, 33.57‐fold) were used to evaluate cross‐resistance and fitness costs as well as to determine the resistance mechanism. RESULTS There was no cross‐resistance with common pesticides except for moderate cross‐resistance with cypermethrin (resistance ratio = 10.26‐fold) observed in RS. The activities of metabolic enzymes were measured, and the results showed that mixed function oxidase (MFO) and carboxylate esterase (CarE) in RS increased significantly by 2.92‐ and 2.86‐fold, respectively, compared with SS. In addition, there was no obvious difference in glutathione‐S‐transferase (GST), which indicated that enhanced MFO and CarE activities may be the main mechanisms of detoxification. In the four typical resistance‐related genes, expression of GluCl (4.86‐fold), ABCC2 (3.85‐fold), and CYP6 (2.94‐fold) in RS were significantly promoted, but expression of GST was not. The clone and sequence of the PxGluClα subunit displayed six mutations that could lead to changes in the amino acid residues. CONCLUSION High suitability related to tenvermectin A resistance was observed in RS, and it was found that the developmental stages of RS were significantly shortened and the survival rate of females was reduced. In addition, the mechanism of resistance to tenvermectin A may be regulated by the glutamate‐gated chloride channel, ATP‐binding cassette transporter, and MFO. In general, the study of resistance and biochemical mechanisms can provide beneficial and rational information for the management of resistance in P. xylostella.