title: Genetics of resistance to phosphine in Rhyzopertha dominica (Coleoptera: Bostrichidae).
abstract: The inheritance of resistance to phosphine was studied in two strains of the lesser grain borer, Rhyzopertha dominica (F.), labeled 'Weak-R' and 'Strong-R'. These strains were purified versions of field-selected populations collected in Queensland, Australia. Weak-R and Strong-R were, respectively, 23.4 times (20-h exposure) and 600 times (48-h exposure) resistant to phosphine compared with a reference susceptible strain (S-strain). Each -R strain was crossed with the S-strain and the response to phosphine was measured in their respective F1, F2, and F1-backcross (F1-BC) progenies. Data from testing of reciprocal F1 progeny indicated that resistance in Weak-R was autosomal and incompletely recessive with a degree of dominance -0.96. Modified chi-square analysis and contingency analysis of the observed response to phosphine of F1-BC and F2 progenies rejected the hypothesis of single gene inheritance of resistance. Analysis of the response of the F1, F2, and F1-BC progeny from the Strong-R x S-strain cross also rejected the null hypothesis for single gene resistance. Resistance in the Strong-R strain was autosomal and incompletely recessive with a degree of dominance of -0.64. The Weak-R and Strong-R strains were then crossed. Analysis ofthe F1 and F2 progenies of this reciprocal cross revealed that the strong resistance phenotype was coded by a combination of the genes already present in the Weak-R genotype plus an extra major, incompletely recessive gene. There was also evidence of a minor dominant gene present in approximately 5% of Strong-R individuals.
authors.affiliation: Queensland Department of Primary Industries, Indooroopilly, Australia. Pat.Collins@dpi.qld.gov.au
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Collins
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Daglish
authors.forename: Mervyn
authors.initials: M
authors.lastname: Bengston
authors.forename: Tina M
authors.initials: TM
authors.lastname: Lambkin
authors.forename: Hervoika
authors.initials: H
authors.lastname: Pavic
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000235:genetics*; D005260:Female; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides; D008297:Male; D010720:Phosphines
chemical_list: D007306:Insecticides; D010720:Phosphines; C044646:phosphine