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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #391803

Research Project: Sustainable Pest Management for Arid-Land Agroecosystems

Location: Pest Management and Biocontrol Research

Title: Responses to Bt toxin Vip3Aa by pink bollworm larvae resistant or susceptible to Cry toxins

Author
item TABASHNIK, BRUCE - University Of Arizona
item UNNITHAN, GOPALAN CHANDRA - University Of Arizona
item YELICH, ALEXANDER - University Of Arizona
item Fabrick, Jeffrey
item DENNEHY, TIMOTHY - University Of Arizona
item CARRIERE, YVES - University Of Arizona

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2022
Publication Date: 9/3/2022
Citation: Tabashnik, B.E., Unnithan, G.N., Yelich, A., Fabrick, J.A., Dennehy, T.J., Carriere, Y. 2022. Responses to Bt toxin Vip3Aa by pink bollworm larvae resistant or susceptible to Cry toxins. Pest Management Science. 78:3973-3979. https://doi.org/10.1002/ps.7016.
DOI: https://doi.org/10.1002/ps.7016

Interpretive Summary: Genetically engineered crops producing insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized management of some important insect pests. However, pest resistance to Bt crops diminishes their efficacy and reduces the many benefits of this technology. Resistance to crystalline (Cry) proteins produced in Bt crops has occurred for numerous insect species and has spurred the search for novel proteins with insecticidal activity, including the Bt vegetative insecticidal protein Vip3A. Here, an ARS scientist at Maricopa, AZ and collaborators report the results of lab diet bioassays evaluating responses to Vip3Aa by pink bollworm (Pectinophora gossypiella), one of the world’s most damaging pests of cotton. Overall, Vip3Aa was less potent against pink bollworm larvae susceptible to the Cry toxins, Cry1Ac or Cry2Ab. Conversely, Vip3Aa was more potent than Cry1Ac or Cry2Ab against lab strains highly resistant to those Cry toxins. Five Cry-susceptible field populations from the United States tested in 2005 were also less susceptible to Vip3Aa than a Cry-susceptible lab strain (APHIS-S). Relative to APHIS-S, we found no evidence for significant cross-resistance to Vip3Aa in strains selected in the lab for resistance to Cry1Ac or both Cry1Ac and Cry2Ab, consistent with predictions based on the lack of shared midgut receptors between these toxins and previous results from other lepidopterans. These results indicate that although Vip3Aa is not highly effective against pink bollworm, the moderate efficacy against Cry-resistant insects might be useful as one component of integrated pest management programs where resistant insects are present.

Technical Abstract: Transgenic crops that make insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized management of some pests. However, evolution of resistance to Bt toxins by pests diminishes the efficacy of Bt crops. Resistance to crystalline (Cry) Bt toxins has spurred adoption of crops genetically engineered to produce the Bt vegetative insecticidal protein Vip3Aa. Here we used laboratory diet bioassays to evaluate responses to Vip3Aa by pink bollworm (Pectinophora gossypiella), one of the world's most damaging pests of cotton. Against pink bollworm larvae susceptible to Cry toxins, Vip3Aa was less potent than Cry1Ac or Cry2Ab. Conversely, Vip3Aa was more potent than Cry1Ac or Cry2Ab against laboratory strains highly resistant to those Cry toxins. Five Cry-susceptible field populations were less susceptible to Vip3Aa than a Cry-susceptible laboratory strain (APHIS-S). Relative to APHIS-S, significant resistance to Vip3Aa did not occur in strains selected in the laboratory for >'700-fold resistance to Cry1Ac or both Cry1Ac and Cry2Ab. Resistance to Cry1Ac and Cry2Ab did not cause strong cross-resistance to Vip3Aa in pink bollworm, which is consistent with predictions based on the lack of shared midgut receptors between these toxins and previous results from other lepidopterans. Comparison of the Bt toxin concentration in plants relative to the median lethal concentration (LC50) from bioassays may be useful for estimating efficacy. The moderate potency of Vip3Aa against Cry1Ac- and Cry2Ab-resistant and susceptible pink bollworm larvae suggests that Bt cotton producing this toxin together with novel Cry toxins might be useful as one component of integrated pest management.