Resistance of Varroa destructor to pyrethroids: A preliminary analysis in Portugal
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Infestations of Varroa destructor are closely associated with colony collapse in the honey bee (Apis mellifera). Currently, three classes of acaricidal compounds are utilized to combat these infestations: pyrethroids (fluvalinate and flumethrin), organophosphates (coumaphos) and formamidines (amitraz). The first cases of V. destructor resistance to pyrethroids were reported in Italy, followed by numerous instances of resistant populations worldwide. The molecular mechanism of V. destructor resistance to pyrethroids is well understood and primarily linked to an amino acid change at position 925, where a leucine (L) is typically found. At this position, three alleles have been described that confer resistance to pyrethroids, where leucine is substituted by valine (L925V), isoleucine (L925I), or methionine (L925M). A novel mutation at position 918 was described in a population from Spain, where the amino acid methionine, normally found at position 918, was replaced by leucine (M918L). In Portugal, gene variation associated with pyrethroid resistance remains unknown. To investigate this mechanism in V. destructor populations from Portuguese apiaries, DNA was extracted from individual mites. This DNA was PCR-amplified using the primers 273-IF_VD (5′-AAGCCGCCATTGTTACCAGA-3′) and 1973-IR_VD (5’- CTGTTGTTACCGTGGAGCA-3′) and subjected to Sanger sequencing. The expected outcome is that mutations are found in Portugal at both positions 925 and 918, due to its geographical proximity to Spain. These results will contribute to the Portuguese beekeeping sector by facilitating the development of strategies for handling V. destructor resistance.
