Role of the kdr and super-kdr sodium channel mutations in pyrethroid resistance: correlation of allelic frequency to resistance level in wild and laboratory populations of horn flies (Haematobia irritans).
The kdr and super-kdr point mutations found in the insect sodium channel gene are postulated to confer knockdown resistance (kdr) to pyrethroids. Using an allele-specific PCR assay to detect these mutations in individual horn flies, Haematobia irritans (L.), we determined the allelic frequency of the kdr and super-kdr mutations in several wild and laboratory populations. Wild populations with very similar allelic frequencies had resistance levels that ranged widely from 3- to 18-fold relative to a susceptible population. Conversely, the kdr allele frequency in a lab population with 17-fold resistance was nearly double that found in a heavily pressured wild population with 18-fold resistance. We conclude that, although the kdr mutation confers significant levels of pyrethroid resistance, a substantial component of resistance in insecticidally pressured populations is conferred by mechanisms that are PBO-suppressible. High super-kdr allele frequencies were detected in two resistant lab populations, but in wild populations with equivalent resistance the super-kdr allele frequency was very low. Interestingly, in over 1200 individuals assayed, the super-kdr mutation was never detected in the absence of the kdr mutation.
Jamroz
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USDA-ARS Knipling-Bushland Livestock Insects Research Laboratory, Kerrville, TX 78028, USA. rjamroz@ktc.com
Guerrero
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FD
Kammlah
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DM
Kunz
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SE
D000483:Alleles; D000818:Animals; D004175:Diptera / Q000235:genetics*; D005787:Gene Frequency; D005838:Genotype; D019476:Insect Proteins / Q000235:genetics* / Q000502:physiology; D007305:Insecticide Resistance / Q000235:genetics; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D011722:Pyrethrins; D015222:Sodium Channels / Q000235:genetics* / Q000502:physiology
D019476:Insect Proteins; D011722:Pyrethrins; D015222:Sodium Channels