Screening for resistance alleles to Cry1 proteins through targeted sequencing in the native and invasive range of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Authors: TANDY, PETER - University Of Tennessee; LAMOUR, KURT - University Of Tennessee; PLACIDI DE BORTOLI, CAROLINE - University Of Tennessee; Nagoshi, Rodney; EMRICH, SCOTT - University Of Tennessee; JURAT-FUENTES, JUAN LUIS - University Of Tennessee

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2023
Publication Date: 6/13/2023
Citation: Tandy, P., Lamour, K., Placidi De Bortoli, C., Nagoshi, R.N., Emrich, S., Jurat-Fuentes, J. 2023. Screening for resistance alleles to Cry1 proteins through targeted sequencing in the native and invasive range of Spodoptera frugiperda (Lepidoptera: Noctuidae). Journal of Economic Entomology. 116(3):935-944. https://doi.org/10.1093/jee/toad061.
DOI: https://doi.org/10.1093/jee/toad061

Interpretive Summary: The fall armyworm, Spodoptera frugiperda, is a highly polyphagous pest native to the tropical Americas that has spread in the last few years to become a global superpest threatening food and fiber production. Transgenic crops producing insecticidal proteins from the bacterium, Bacillus thuringiensis, are used for effective control of this pest in its native range, yet evolution of practical resistance represents the greatest threat to sustainability of this technology and its potential efficacy in the fall armyworm invasive range. Monitoring for resistance is vital to management approaches to delay fall armyworm resistance to Bt crops. In this study, a scientist at USDA-ARS, CMAVE, Gainesville, FL in collaboration with scientists from the University of Tennessee, Knoxville, performed a new method of DNA sequence analysis of large populations to confirm detection of known and candidate resistance alleles in field-collected fall armyworm from continental USA, Africa (Ghana, Togo and South Africa) and Southeast Asia (Myanmar). Results confirm distribution of a known resistance allele to be limited to Puerto Rico and identify a candidate resistance allele potentially spreading in North America. This study provides valuable information about the distribution of resistant alleles in fall armyworm populations as well as a new method for use in BT resistance monitoring programs.

Technical Abstract: The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a highly polyphagous pest native to the tropical Americas that has spread in the last 6 years to become a global superpest threatening food and fiber production. Monitoring for resistance is vital to management approaches to delay S. frugiperda resistance to Bt crops. DNA-based resistance screening methods would provide higher sensitivity and cost-effectiveness than currently used bioassay-based resistance monitoring. So far, practical S. frugiperda resistance to Bt corn has been genetically linked to mutations in the SfABCC2 gene, providing a model to develop and test monitoring tools. In this study, we performed targeted SfABCC2 sequencing followed by Sanger sequencing to confirm detection of known and candidate resistance alleles to Cry1F corn in field-collected S. frugiperda from continental USA, Africa (Ghana, Togo and South Africa) and Southeast Asia (Myanmar). Results confirm distribution limited to Puerto Rico for a known resistance allele and identify a candidate resistance allele potentially spreading along the migratory route of S. frugiperda in North America. In addition, results detected a candidate resistance allele unique to the invasive S. frugiperda range. Taken together, these results support the use of targeted sequencing in Bt resistance monitoring programs.