Journal of Insect Science (2003) 3 (36), p. 4 (Gahan et al.)

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L.J. Gahan, F. Gould, S.M. Brown, S.W. Baxter and D.G. Heckel (2003)
Linkage mapping reveals a diversity of mechanisms of resistance to Bacillus thuringiensis toxins in Lepidoptera
Journal of Insect Science 3 (36), 4-4
Sixth International Workshop on the Molecular Biology and Genetics of the Lepidoptera, August 25-30, 2003, Kolympari, Crete
Abstract: Insecticidal toxins from Bacillus thuringiensis (Bt) are widely utilized in foliar sprays and transgenic plants to control Lepidopteran pests of agricultural crops, but the development of resistance poses a threat to their sustainable use. The most common type of resistance to Bt toxins ("Mode 1") is characterized by recessive inheritance, a high level of resistance to (and reduced midgut binding by) at least one Cry1A toxin, and negligible cross-resistance to Cry1C (Tabashnik et al. 1998, Philosophical Transaction of the Royal Society Series B 353: 1751). A 12-domain member of the cadherin superfamily is expressed on larval midgut epithelial membranes and is involved with Cry1A mode of action in Lepidoptera. Mode 1 resistance is caused by mutations in this cadherin in two Lepidopteran species, Heliothis virescens (Gahan et al. 2001, Science 293: 857) and Pectinophora gossypiella (Morin et al. 2003, PNAS USA 100:5004), making this gene a prime target for developing DNA-based screening methods. However, using a linkage-mapping approach, we have been able to show that Mode 1 resistance in a third species, diamondback moth Plutella xylostella, has a different genetic basis. This indicates that screening for mutations in the cadherin gene, while useful in specific cases, may not provide a universal method for detecting Bt resistance in the field. Moreover, non-Mode-1 resistance in the cotton bollworm, Helicoverpa armigera, as well as Heliothis virescens, is caused by a different mechanism altogether. We discuss the implications of this complex genetic basis of resistance for the durability of Bt as a pest control strategy, and for our understanding of Bt mode of action.
Database assignments for author(s): David G. Heckel

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

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Helicoverpa armigera
Plutella xylostella
Chloridea virescens
Pectinophora gossypiella
Bacillus thuringiensis Cry1A-toxin (entomopathogen) Helicoverpa armigera
Bacillus thuringiensis Cry1A-toxin (entomopathogen) Plutella xylostella
Bacillus thuringiensis Cry1A-toxin (entomopathogen) Chloridea virescens
Bacillus thuringiensis Cry1A-toxin (entomopathogen) Pectinophora gossypiella
Bacillus thuringiensis Cry1C-toxin (entomopathogen)