Global patterns of insect resistance to transgenic Bt crops: The first 25 years

Authors: TABASHNIK, BRUCE - University Of Arizona; Fabrick, Jeffrey; CARRIERE, YVES - University Of Arizona

Submitted to: Journal of Economic Entomology
Publication Type: Review Article
Publication Acceptance Date: 10/27/2022
Publication Date: 1/4/2023
Citation: Tabashnik, B.E., Fabrick, J.A., Carriere, Y. 2023. Global patterns of insect resistance to transgenic Bt crops: The first 25 years. Journal of Economic Entomology. 116(2):297-309. https://doi.org/10.1093/jee/toac183.
DOI: https://doi.org/10.1093/jee/toac183

Interpretive Summary: Transgenic plants producing insecticidal proteins from Bacillus thuringiensis (Bt) are grown widely to control pests, but evolution of insect resistance has reduced the efficacy of Bt crops. Here, an ARS scientist at Maricopa, AZ and collaborators analyzed global resistance monitoring data for the first 25 years of cultivation of Bt crops including corn, cotton, soybean, and sugarcane. A total of 73 cases were examined including 24 pest species from 12 countries. The cases of practical resistance rose from 3 in 2005 to 26 in 2020. Practical resistance has been documented in some populations of 11 pest species, collectively affecting nine widely used crystalline (Cry) Bt toxins in seven countries. Conversely, 30 cases reflect no decrease in susceptibility to Bt crops in populations of 15 pest species in nine countries. The remaining 17 cases provide early warnings of resistance, which entail genetically based decreases in susceptibility without evidence of reduced efficacy. The early warnings involve four Cry toxins and the Bt vegetative insecticidal protein Vip3Aa. Factors expected to favor sustained susceptibility include abundant refuges of non-Bt host plants, recessive inheritance of resistance, low resistance allele frequency, fitness costs, incomplete resistance, and redundant killing by multi-toxin Bt crops. Also, sufficiently abundance refuges can overcome some unfavorable conditions for other factors. These insights may help to increase the sustainability of current and future transgenic insecticidal crops.

Technical Abstract: Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have improved pest management and reduced reliance on insecticide sprays. However, evolution of practical resistance by some pests has reduced the efficacy of Bt crops. We analyzed global resistance monitoring data for 24 pest species based on the first 25 years of cultivation of Bt crops including corn, cotton, soybean, and sugarcane. Each of the 73 cases examined represents the response of one pest species in one country to one Bt toxin produced by one or more Bt crops. The cases of practical resistance rose from 3 in 2005 to 26 in 2020. Practical resistance has been documented in some populations of 11 pest species (nine lepidopterans and two coleopterans), collectively affecting nine widely used crystalline (Cry) Bt toxins in seven countries. Conversely, 30 cases reflect no decrease in susceptibility to Bt crops in populations of 15 pest species in nine countries. The remaining 17 cases provide early warnings of resistance, which entail genetically based decreases in susceptibility without evidence of reduced efficacy. The early warnings involve four Cry toxins and the Bt vegetative insecticidal protein Vip3Aa. Factors expected to favor sustained susceptibility include abundant refuges of non-Bt host plants, recessive inheritance of resistance, low resistance allele frequency, fitness costs, incomplete resistance, and redundant killing by multi-toxin Bt crops. Also, sufficiently abundant refuges can overcome some unfavorable conditions for other factors. These insights may help to increase the sustainability of current and future transgenic insecticidal crops.