title: Genetics and evidence for an esterase-associated mechanism of resistance to indoxacarb in a field population of diamondback moth (Lepidoptera: Plutellidae).
abstract: Bioassays (at generation G2) with a newly collected field population (designated CH3) of Plutella xylostella L. from farmers' fields in the Cameron Highlands, Malaysia, indicated resistance ratios of 813-, 79-, 171-, 498- and 1285-fold for indoxacarb, fipronil, spinosad, deltamethrin and Bacillus thuringiensis toxin Cry1Ac respectively compared with a laboratory susceptible population (Lab-UK). At G2 the field-derived population was divided into two subpopulations: one was selected (G2 to G7) with indoxacarb (indoxa-SEL), while the second was left unselected (UNSEL). A significant reduction in the resistance ratio for each compound was observed in UNSEL at G8. For indoxa-SEL, bioassays at G8 found that selection with indoxacarb gave a resistance ratio of 2594 compared with Lab-UK and of 90 compared with UNSEL. The toxicity of fipronil, spinosad and deltamethrin was not significantly different in indoxa-SEL at G8 compared with G2 but was significantly greater than UNSEL at G8. The toxicity of Cry1Ac was significantly reduced in indoxa-SEL at G8 compared with G2 but was also significantly greater than UNSEL at G8. This suggests that indoxacarb selection maintained resistance to these compounds in the indoxa-SEL population. Synergist studies indicated that resistance to indoxacarb in indoxa-SEL was esterase associated. Logit regression analysis of F1 reciprocal crosses between indoxa-SEL and Lab-UK indicated that resistance to indoxacarb was inherited as an autosomal, incompletely recessive (D(LC) = 0.35) trait. Tests of monogenic inheritance suggested that resistance to indoxacarb was controlled by a single locus.
authors.affiliation: Division of Biology, Faculty of Natural Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, UK. h.a.sayyed@sussex.ac.uk
authors.forename: Ali H
authors.initials: AH
authors.lastname: Sayyed
authors.forename: Denis J
authors.initials: DJ
authors.lastname: Wright
mesh_terms: D000818:Animals; D004950:Esterases / Q000378:metabolism*; D040582:Inheritance Patterns; D007305:Insecticide Resistance / Q000235:genetics* / Q000502:physiology; D007306:Insecticides / Q000378:metabolism*; D007928:Lethal Dose 50; D009036:Moths / Q000201:enzymology* / Q000235:genetics*; D010078:Oxazines / Q000378:metabolism*; D012641:Selection, Genetic
chemical_list: D007306:Insecticides; D010078:Oxazines; C401104:indoxacarb; D004950:Esterases