An Amino Acid Substitution (L925V) Associated with Resistance to Pyrethroids in Varroa destructor

Joel González-Cabrera,T G Emyr Davies,Linda M Field,Martin S Williamson,Peter J Kennedy,Guy Smagghe

doi:10.1371/journal.pone.0082941

Abstract

The Varroa mite, Varroa destructor, is an important pest of honeybees and has played a prominent role in the decline in bee colony numbers over recent years. Although pyrethroids such as tau-fluvalinate and flumethrin can be highly effective in removing the mites from hives, their intensive use has led to many reports of resistance. To investigate the mechanism of resistance in UK Varroa samples, the transmembrane domain regions of the V. destructor voltage-gated sodium channel (the main target site for pyrethroids) were PCR amplified and sequenced from pyrethroid treated/untreated mites collected at several locations in Central/Southern England. A novel amino acid substitution, L925V, was identified that maps to a known hot spot for resistance within the domain IIS5 helix of the channel protein; a region that has also been proposed to form part of the pyrethroid binding site. Using a high throughput diagnostic assay capable of detecting the mutation in individual mites, the L925V substitution was found to correlate well with resistance, being present in all mites that had survived tau-fluvalinate treatment but in only 8 % of control, untreated samples. The potential for using this assay to detect and manage resistance in Varroa-infected hives is discussed.

Highlights

The infestation of Western honey bees (Apis mellifera) by the ectoparasitic mite Varroa destructor has been an important factor contributing to the increasing losses of colonies reported in many European countries [1]
The RNA was reverse transcribed into cDNA to amplify the four fragments encompassing domains I, II, III and IV of the V. destructor voltage-gated sodium channel (VGSC) (Fig. 1, Table 3)
Samples DL, C and D showed a G to C polymorphism at base 3952 compared to samples V8 and V10 causing an arginine (CGT) to glycine (GGT) substitution at channel residue 1318 (Varroa numbering as this region is not conserved in the housefly VGSC)

Summary

Introduction

The infestation of Western honey bees (Apis mellifera) by the ectoparasitic mite Varroa destructor has been an important factor contributing to the increasing losses of colonies reported in many European countries [1]. Tau-fluvalinate and flumethrin) among the most useful products for providing selective and effective control of the parasite without harming the bees on which they feed [1]. Widespread use of these compounds, as with most pesticides, has led to selection for resistance and reports of reduced efficacy of pyrethroid products against Varroa are common place. Following initial reports in Europe during the mid 1990s [4], resistance has been reported from most parts of the world [4,5,6,7,8,9,10,11,12] and has resulted in a gradual decline in the use of pyrethroids and their replacement by less effective chemical treatments [13]

Methods

Results

Conclusion