title: Investigation of resistance mechanisms to fipronil in diamondback moth (Lepidoptera: Plutellidae).
abstract: The SZ-F strain of Plutella xylostella (L.) (Lepidoptera: Plutellidae) was derived from a field-collected strain (SZ) by 20 generations of continuous selection with fipronil. The selection resulted in 300-fold increase in resistance to fipronil, and 3.5- and 6.5-fold cross-resistance to dieldrin and endosulfan, respectively, in the SZ-F strain compared with the unselected SZ strain. Analysis of detoxification enzyme activities and bioassay with synergists indicated that metabolic mechanisms are not important to fipronil resistance of the SZ-F strain and that the fipronil resistance is most likely attributed to target site insensitivity. The genomic DNA fragments flanking the second membrane-spanning region of Rdl gamma-aminobutyric acid (GABA) receptor gene from P. xylostella, PxRdl, were cloned and sequenced. A single allele of the PxRdl gene (encoding A302 or allele PxRdl-Ala) was found in both the Roth (susceptible) and SZ strains. In addition to the wild-type allele PxRdl-Ala, the resistant SZ-F strain carried a mutant PxRdl allele with the conserved amino acid replacement A302(GGC)--> S302(TCC) (allele PxRdl-Ser). The mutant PxRdl-Ser allele frequency in the SZ-F strain was 30%. After treatment of 20 mg/l fipronil on the SZ-F strain, the PxRdl-Ser allele frequency in the survivors increased to 57%. High frequency of the PxRdl-Ala allele remaining in the resistant SZ-F strain suggested that the A302S mutation in the PxRdl gene is partially associated with fipronil resistance and that other mutation(s) in the PxRdl gene or other Rdl-like subunit(s) may contribute to fipronil resistance.
authors.affiliation: Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Ageng
authors.initials: A
authors.lastname: Li
authors.forename: Yihua
authors.initials: Y
authors.lastname: Yang
authors.forename: Shuwen
authors.initials: S
authors.lastname: Wu
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Yidong
authors.initials: Y
authors.lastname: Wu
mesh_terms: D000409:Alanine; D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D004026:Dieldrin; D004726:Endosulfan; D007305:Insecticide Resistance / Q000235:genetics / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology; D008969:Molecular Sequence Data; D009036:Moths / Q000187:drug effects / Q000502:physiology*; D020125:Mutation, Missense; D011720:Pyrazoles / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D012694:Serine
chemical_list: D007306:Insecticides; D011720:Pyrazoles; D012694:Serine; D004026:Dieldrin; D000409:Alanine; D004726:Endosulfan; C082360:fipronil