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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 #363585
Research Project: Ecologically Based Pest Management in Western Crops Such as Cotton

Location: Pest Management and Biocontrol Research

Title: Gossypol in cottonseed increases the fitness cost of resistance to Bt cotton in pink bollworm

Author
item CARRIERE, YVES - University Of Arizona
item YELICH, ALEX - University Of Arizona
item DEGAIN, BEN - University Of Arizona
item HARPOLD, VIRGINIA - University Of Arizona
item UNNITHAN, GOPALAN - University Of Arizona
item KIM, JAE - Monsanto Company
item Mathew, Lolita
item HEAD, GRAHAM - Monsanto Company
item RATHORE, KEERTI - Texas A&M University
item Fabrick, Jeffrey
item TABASHNIK, BRUCE - University Of Arizona

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2019
Publication Date: 8/9/2019
Publication URL: https://handle.nal.usda.gov/10113/6570100
Citation: Carriere, Y., Yelich, A.J., Degain, B., Harpold, V.S., Unnithan, G.C., Kim, J.H., Mathew, L.G., Head, G.P., Rathore, K.S., Fabrick, J.A., Tabashnik, B.E. 2019. Gossypol in cottonseed increases the fitness cost of resistance to Bt cotton in pink bollworm. Crop Protection. 126. https://doi.org/10.1016/j.cropro.2019.104914.
DOI: https://doi.org/10.1016/j.cropro.2019.104914

Interpretive Summary: Although transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) provide many benefits and are widely used, pest resistance to such Bt crops threatens to reduce their continued efficacy. Two major strategies are currently used to delay resistance to Bt crops, including the use of two or more Bt proteins with different modes of action (pyramid strategy) and the simultaneous planting of non-Bt crops with Bt crops to produce an excess of Bt-susceptible insects that can mate with rare resistant individuals produced from Bt fields (refuge strategy). However, additional strategies are needed to extend the life of currently available and/or new Bt proteins and to delay the onset of pest resistance to Bt crops. Here, we test a third possible strategy to delay Bt resistance that involves the manipulation of fitness costs associated with Bt resistant insect populations. Specifically, we tested whether the plant defensive compound gossypol in cottonseed increases costs associated with resistance to Bt toxin Cry1Ac in pink bollworm (Pectinophora gossypiella), a cosmopolitan pest that feeds primarily on cottonseed. Our results show that higher gossypol concentrations in cottonseed increase the fitness cost affecting pink bollworm survival. Hence, designing insecticidal crops and refuge plants that exploit the vulnerability of resistant insects to plant defensive compounds could improve resistance management.

Technical Abstract: Fitness costs of resistance to Bacillus thuringiensis (Bt) toxins can delay or counter the evolution of insect resistance to transgenic Bt crops. Here we tested the hypothesis that the plant defensive compound gossypol in cottonseed increases costs associated with resistance to Bt toxin Cry1Ac in pink bollworm (Pectinophora gossypiella), a cosmopolitan pest that feeds primarily on cottonseed. Previous work showed pink bollworm resistance to Cry1Ac produced by Bt cotton is associated with mutations disrupting a gene encoding a cadherin protein that binds Cry1Ac in susceptible larvae. We used larvae from two strains of pink bollworm, each harboring an intermediate frequency of a different cadherin allele linked with resistance. We tested larvae from both strains on two types of non-Bt cotton that differed nine-fold in the gossypol concentration in their seeds: a transgenic cultivar engineered for low gossypol production and its untransformed parental cultivar. After 10 days of larval feeding on bolls, the resistance allele frequency was significantly lower in larvae from the conventional cotton than transgenic cotton. These results imply the higher gossypol concentration in the conventional cottonseed increased the fitness cost affecting survival. Using a population genetics model, we estimated this increase in survival cost was at least 32%. We also detected a recessive fitness cost reducing larval weight in both strains of pink bollworm that did not differ between the two cotton cultivars. Designing insecticidal crops and refuge plants that exploit the vulnerability of resistant insects to plant defensive compounds could improve resistance management.