Journal of Insect Science (2006) 6 (46), 47-48

E.J.G. Pereira, B.A. Lang, M. Zhuang, N.P. Storer and B.D. Siegfried (2006)
Development and characterization of European corn borer resistance to the Cry1F toxin from Bacillus thuringiensis
Journal of Insect Science 6 (46), 47-48
in M. Adams et al. [editors] Abstracts of the Fifth International Symposium on Molecular Insect Science (May 20-24, 2006, Tucson, Arizona USA), 76 pp.
Abstract: Evolution of resistance by insect-pests is the greatest threat to the continued success of Bacillus thuringiensis toxins used in sprays or in transgenic crop plants such as maize expressing the Cry1F toxin for control of lepidopteran pests. Availability of laboratory-selected insect strains allows determination of biochemical mechanisms of resistance that can evolve as well as identification of genes involved. A strain of European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), obtained from field collections throughout the U.S. Corn Belt in 1996 was selected in the laboratory for resistance to Cry1F by exposure to the toxin incorporated into artificial diet. The selected strain developed more than 3000-fold resistance to Cry1F, yet it was as susceptible to Cry1Ab and Cry9C as the unselected control strain. Only a low level of cross resistance (7-fold) to Cry1Ac was observed. Dose-response of reciprocal parental crosses indicated that the resistance is autosomal and recessive. Backcross of the F₁ generation with the selected strain revealed that a single locus or a set of tightly linked loci is responsible for the resistance. Analyses using ligand-toxin immunoblotting and Surface Plasmon Resonance to measure Cry1F binding to brush border membrane vesicles of midgut epithelia from susceptible and resistant larvae showed no reduced binding associated with resistance. Additionally, expression of two putative Cry1-receptor proteins, cadherin and aminopeptidase, was similar in the control and selected strains. Moreover, no altered activity of luminal gut proteases and proteolytic processing of the toxin were observed in the resistant strain. Although the resistance mechanism remains uncertain, there is no direct evidence that altered binding and proteolytic processing of toxin are involved. The resistance mechanism in this Cry1F-selected strain of corn borer appears to be specific and maybe distinct from previously identified resistance mechanisms in Lepidoptera. Follow-up studies are ongoing to isolate the resistance gene(s) and develop molecular probes for monitoring evolution of resistance in the field.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Eliseu José G. Pereira, Blair D. Siegfried

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

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ostrinia nubilalis	Maize/corn (Zea mays)
Bacillus thuringiensis genes in crops (entomopathogen)	Ostrinia nubilalis	Maize/corn (Zea mays)
Bacillus thuringiensis Cry1F-toxin (entomopathogen)	Ostrinia nubilalis	Maize/corn (Zea mays)