ARS | Publication request: Increased toxicity of Bacillus thuringiensis Cry3Aa against Crioceris quatuordecimpunctata, Phaedon brassicae and Colaphellus bowringi by a Tenebrio molitor cadherin fragment

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2011
Publication Date: March 14, 2011
Citation: Gao, Y., Jurat-Fuentes, J., Oppert, B.S., Fabrick, J.A., Lui, C.A., Gao, J., Lei, Z. 2011. Increased toxicity of Bacillus thuringiensis Cry3Aa against Crioceris quatuordecimpunctata, Phaedon brassicae and Colaphellus bowringi by a Tenebrio molitor cadherin fragment. Pest Management Science. 67(9): 1076-1081. http://dx.doi.org/10.1002/ps.2149.

Interpretive Summary: Bacillus thuringiensis (Bt) is a bacteria used to control insect pests. Bt generally does not kill beetle pests, limiting Bt use in integrated pest management. We evaluated a novel peptide from a beetle toxin receptor to determine the potential to enhance the activity of Bt toxins against beetle pests of vegetables in China. When the peptide was added to the Bt toxin Cry3Aa, BT was as much as 15.3-fold more effective for control of these pests. This demonstrates that the peptide has potential to be used in Bt sprays or incorporated into transgenic Bt crops to protect against coleopteran pests.

Technical Abstract: BACKGROUND: Biopesticides containing Cry insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are effective against many lepidopteran pests, but there is a lack of Bt-based pesticides to efficiently control important coleopteran pests. Based on the reported increase of Bt toxin oligomerization by a polypeptide from the Cry3Aa receptor cadherin in Tenebrio molitor (Coleoptera: Tenebrionidae), we hypothesized that this cadherin peptide, rTmCad1p, would enhance Cry3Aa toxicity towards coleopteran larvae. To test this hypothesis, we evaluated the relative toxicity of Cry3Aa with or without rTmCad1p against damaging chrysomelid vegetable pests of China. RESULTS: Cry3Aa toxicity was evaluated in the spotted asparagus beetle (Crioceris quatuordecimpunctata), cabbage leaf beetle (Colaphellus bowringi), and daikon leaf beetle (Phaedon brassicae). To assess the effect of rTmCad1p on Cry3Aa toxicity, neonate larvae were fed Cry3Aa toxin alone or in combination with increasing amounts of rTmCad1p. The data demonstrated that Cry3Aa toxicity was significantly increased in all three vegetable pests, resulting in as much as a 15.3-fold increase in larval mortality. CONCLUSION: The application of rTmCad1p to enhance Cry3Aa insecticidal activity has potential for use in increasing range and activity levels against coleopteran pests displaying low susceptibility to Bt-based biopesticides.