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Keywords:

  • honey bee;
  • kdr resistance;
  • sodium channel;
  • tau-fluvalinate;
  • Varroa destructor

Abstract

BACKGROUND

Sodium channels (SCs) in mites and insects are target sites for pesticides, including pyrethroids. Point mutations in the SC gene have been reported to change the structural conformation of the protein and its sensitivity to pesticides. To find mutations in the SC gene of the mite Varroa destructor (VmNa), the authors analysed the VmNa gene sequences available in GenBank and prepared specific primers for the amplification of two fragments containing the regions coding for (i) the domain II S4–S6 region (bp 2805–3337) and (ii) the domain III S4-3′ terminus region (bp 4737–6500), as determined according to the VmNa cDNA sequence AY259834.

RESULTS

Sensitive and resistant mite populations did not differ in the amino acid sequences of the III S4-3′ terminus VmNa region. However, differences were found in the IIS4–IIS6 fragment. In the resistant population, the mutation C(3004) [RIGHTWARDS ARROW] G resulted in the substitution L(1002) [RIGHTWARDS ARROW] V (codon ctg [RIGHTWARDS ARROW] gtg) at the position equivalent to that of the housefly L925 in the domain II S5 helix. Additionally, the mutation F(1052) [RIGHTWARDS ARROW] L (codon ttc [RIGHTWARDS ARROW] ctc) at the position equivalent to that of the housefly F975 in the domain II P-loop connecting segments S5 and S6 was detected in both the resistant and sensitive populations.

CONCLUSION

All individuals that survived the tau-fluvalinate treatment in the bioassay harboured the L(1002) [RIGHTWARDS ARROW] V mutation combined with the F(1052), while dead individuals from both the sensitive and resistant populations harboured mostly the L(1002) residue and either of the two residues at position 1052. © 2013 Society of Chemical Industry