A Geographical Polymorphism in a Voltage-gated Sodium Channel Gene in the Mite, Varroa destructor, from Korea

Varroa destructor is an ecto-parasite mite and worldwide pest of the honey bee Apis mellifera L. The pyrethroid tau-fluvalinate (Apistan), an acaricide has been used for varroa mite control since the mid 1980s. Even though resistance to tau-fluvalinate in varroa mites have been reported from Europe,Israel, and USA, the tau-fluvalinate resistance in varroa mites has never been investigated in Korea. We conducted bioassay in several apiaries located different regions in Korea.The tau-fluvalinate resistances in varroa mites in Anseong and Gwangju apiaries were statistically higher than in Cheongsong, Chuncheon, and Gochang apiaries. Since tau-fluvalinate is known to act on the sodium channels directly, partial genomic DNA fragments of a voltage-sensitive sodium channel gene from varroa mites were cloned and sequenced. Two novel mutations in sodium channels of varroa mites were present in eight apiaries. Two mutations might be a geographical polymorphism of sodium channel of varroa mites in Korea. The nucleotide sequences of two clones were deposited in the GenBank under accession number FJ216961 and FJ216962, respectively.