ARS | Publication request: Identification of a mutation associated with permethrin resistance in the para-type sodium channel of the stable fly (Diptera: Muscidae)

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 25, 2010
Publication Date: February 20, 2011
Citation: Olafson, P.U., Pitzer, J.B., Kaufman, P.E. 2011. Identification of a mutation associated with permethrin resistance in the para-type sodium channel of the stable fly (Diptera: Muscidae). Journal of Economic Entomology. 104(1):250-257.

Interpretive Summary: The insect sodium channel is of particular interest for evaluating resistance to pyrethroid insecticides because; it is the target molecule for this major class of neurotoxic insecticides. To date, little is known regarding possible mutations in the stable fly that might account for increased resistance to pyrethroid insecticides. A portion of the stable fly sodium channel gene (domain II), was compared between individuals of a laboratory strain selected for resistance to permethrin and the unselected, parental generation. A single base difference resulting in a leucine to histidine amino acid change was identified (Leu1014His), and its location corresponded with that observed for knockdown resistance (kdr) mutations in other insects. As a result, the allele was designated “kdr-his”. A PCR-based assay was developed to assess the frequency of this mutation in genomic DNA of individual stable flies from the laboratory selections, which provided further evidence that the kdr-his allele accounts for the observed level of permethrin resistance in the selected strain. The assay was then utilized to evaluate the frequency of the mutation from five, field-collected populations originating from three horse farms near Ocala, FL, one horse farm near Gainesville, FL, and one dairy farm near Hague, FL. Frequency of the kdr-his allele ranged from 0.46 to 0.78, supporting further investigation of allele prevalence throughout the stable fly season and in response to field insecticide application.

Technical Abstract: The insect sodium channel is of particular interest for evaluating resistance to pyrethroids because it is the target molecule for this major class of neurotoxic insecticides. The stable fly sodium channel coding sequence representing domains IS6 thru IVS6 was isolated, and the domain II coding sequence compared between individuals of a laboratory strain selected for resistance to permethrin and the unselected, parental generation. A point mutation resulting in a leucine to histidine amino acid change was identified (Leu1014His), and its location corresponded with that observed for knockdown resistance (kdr) mutations in other insects. As a result, the allele was designated “kdr-his”. A molecular assay was developed to assess the frequency of this mutation in genomic DNA of individual stable flies from the laboratory selections, which provided further evidence that the kdr-his allele accounts for the observed level of permethrin resistance in the selected strain. The assay was then utilized to evaluate the frequency of the mutation from five, field-collected populations originating from three horse farms near Ocala, FL, one horse farm near Gainesville, FL, and one dairy farm near Hague, FL. Frequency of the kdr-his allele ranged from 0.46 to 0.78, supporting further investigation of allele prevalence throughout the stable fly season and in response to field insecticide application.