Journal of Economic Entomology (2006) 99, 494-501

A.P. Alves, T.A. Spencer, B.E. Tabashnik and B.D. Siegfried (2006)
Inheritance of resistance to the Cry1Ab Bacillus thuringiensis toxin in Ostrinia nubilalis (Lepidoptera: Crambidae)
Journal of Economic Entomology 99 (2), 494-501
Abstract: Laboratory selection with Cry1Ab, the predominant Bacillus thuringiensis (Bt) toxin in transgenic corn, Zea mays L., produced >1000-fold resistance in two laboratory strains of European corn borer, Ostrinia nubilalis (Hübner). We tested the offspring of various crosses to determine the mode of inheritance of resistance to Cry1Ab. Patterns of inheritance of resistance were similar in the two resistant strains. The progeny of reciprocal F₁ crosses (resistant male × susceptible female and vice versa) responded alike in bioassays, indicating autosomal inheritance. The median lethal concentrations (LC₅₀ values) of F₁ were intermediate between the resistant and susceptible parents, indicating approximately additive inheritance. However, the dominance of resistance increased as the concentration of Cry1Ab decreased. Analysis of progeny from backcrosses (F₁ × susceptible strain) suggests that resistance was controlled by more than one locus. In particular, the fit of observed to expected mortality improved as the number of putative loci increased from 1 to 10. The polygenic nature of resistance in these two laboratory strains suggests that major genes for resistance to Cry1Ab were not common in the founding populations of O. nubilalis. A low initial frequency of major genes for Cry1Ab resistance might be an important factor in delaying evolution of resistance to Bt corn in this pest.
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Full text of article
Database assignments for author(s): Blair D. Siegfried, Bruce E. Tabashnik

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ostrinia nubilalis		Italy
	Ostrinia nubilalis		U.S.A. (mid N)
Bacillus thuringiensis genes in crops (entomopathogen)	Ostrinia nubilalis	Maize/corn (Zea mays)
Bacillus thuringiensis Cry1A-toxin (entomopathogen)	Ostrinia nubilalis	Maize/corn (Zea mays)