Association of voltage-gated sodium channel mutations with field-evolved pyrethroid resistant phenotypes in soybean aphid and genetic markers for their detection

Authors: VALMORBIDA, IVAIR - Iowa State University; HOHENSTEIN, JESSICA - Iowa State University; Coates, Brad; BEVILAQUA, JULIA - Universidade Federal De Santa Maria; MENGER, JAMES - University Of Minnesota; HODGSON, ERIN - Iowa State University; KOCH, ROBERT - University Of Minnesota; O'NEAL, MATTHEW - Iowa State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2021
Publication Date: 7/14/2022
Citation: Valmorbida, I., Hohenstein, J.D., Coates, B.S., Bevilaqua, J.G., Menger, J., Hodgson, E.W., Koch, R.L., O'Neal, M.E. 2022. Association of voltage-gated sodium channel mutations with field-evolved pyrethroid resistant phenotypes in soybean aphid and genetic markers for their detection. Scientific Reports. 12.Article 12020. https://doi.org/10.1038/s41598-022-16366-1.
DOI: https://doi.org/10.1038/s41598-022-16366-1

Interpretive Summary: Soybean aphids are a pest of soybean crops across the Midwest United States that harm plant health by direct feeding and spreading of disease-causing viruses. The ability of farmers to control crop damage and yield loss is problematic due to the development of pyrethroid insecticide resistance by soybean aphid. The genetic mechanism of soybean aphid resistance remained relatively unknown until a USDA researcher along with a team of university collaborators identified mutations, unique to resistant aphids, in the voltage-gated sodium channel (vgsc) gene. Analogous mutations in other insects are known to reduce the binding of pyrethroid insecticides to the vgsc protein and cause resistance. Genetic markers were developed and used to determine that the frequency of these vgsc mutations are significantly increased in field populations after pyrethroid applications. The genetic markers are able to accurately predict pyrethroid resistance in soybean aphids and are valuable tools for monitoring for resistance and the evaluation of strategies to reduce the spread of resistance. This research will be of interest to university, government, and industry stakeholders, as well as regulatory agencies interested in understanding the factors causing insecticide resistance in arthropod pest species, and developing tools to monitor for resistance in field populations.

Technical Abstract: The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is an invasive species in the United States. The extensive use of pyrethroid insecticides to manage A. glycines since introduction has contributed to field-evolved resistance. A colony, SBA-MN1-2017, was initiated from A. glycines collected at fields following pyrethroid insecticide control failures. SBA-MN1-2017 has a lambda-cyhalothrin resistance ratio (RR) 48.23-fold greater than a susceptible control colony (SBA-ISU-B1), which is conferred by a mechanism independent of detoxification as demonstrated by lack of effect by pyrethroid synergist. Sequencing of full-length cDNAs and genomic DNA fragments from the voltage-gated sodium channel (vgsc) of SBA-ISU-B1 and three additional resistant populations (RR range 3.94 to 38.57), detected two non-synonymous mutations in the resistant aphids; a classic knockdown resistance (kdr) leucine to phenylalanine mutation at A. glycines vgsc protein position 1024 (L1024F), and a methionine to isoleucine change at position 928 (M928I). Genetic markers detecting L1024 and M928I mutant alleles demonstrated the association of heterozygote genotypes encoding kdr (1024 L/F) and super-kdr (1024 L/F + 928 M/I) with survival in laboratory bioassays and following application of pyrethroid insecticide in field trials. Although we show that both kdr and super-kdr genotypes are associated with pyrethroid resistance in A. glycines, the greater proportional increase in among survivors of bioassayed and field applied pyrethroid levels suggest the greater contribution of super-kdr to field-evolved resistance traits. Interestingly, these differences in vgsc genotype are not alone explanatory of nearly the 12.25-fold variance in RR estimated among resistant populations. Thus, other mechanisms in combination with mutations in the vgsc are likely to contribute to observed differences in RR in A. glycines. Regardless, the genetic markers developed and validated here are predictive of resistance in field populations, and provide diagnostic tools for application in monitoring and resistance management strategies.