Large-Scale Monitoring of the Frequency of Ryanodine Receptor Target-Site Mutations Conferring Diamide Resistance in Brazilian Field Populations of Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

• Published in: Insects (Basel, Switzerland) Vol. 13; no. 7; p. 626
• Main Authors: Okuma, Daniela M, Cuenca, Ana, Nauen, Ralf, Omoto, Celso
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 13.07.2022; MDPI
• Subjects: Bioassays; Butterflies & moths; Cereal crops; chlorantraniliprole; Corn; Cotton; Crop damage; Crops; Cross-resistance; Damage; Eastern Hemisphere; fall armyworm; flubendiamide; Genetics; Genotyping; High resistance; Insecticide resistance; Insecticides; Laboratories; Monitoring; Mutation; Pest resistance; Pests; Population genetics; Populations; Proteins; Receptors; ryanodine receptor; Ryanodine receptors; Spodoptera frugiperda; Strains (organisms); Tropical environment; Tropical environments; Western Hemisphere; Brazil; United States > US; China; Africa; India; diamide insecticide; target-site resistance; chlorantraniliprole; corn; fall armyworm; Spodoptera frugiperda; ryanodine receptor; flubendiamide; I4790K mutation
• ISSN: 2075-4450; 2075-4450
• DOI: 10.3390/insects13070626

Fall armyworm (FAW), , is an important lepidopteran pest in the Americas, and recently invaded the Eastern Hemisphere. In Brazil, FAW is considered the most destructive pest of corn and cotton. FAW has evolved resistance to many insecticides and (Bt) proteins. Here, a large-scale monitoring was performed between 2019 and 2021 to assess diamide insecticide susceptibility in more than 65 FAW populations sampled in corn and cotton. We did not detect a significant shift in FAW susceptibility to flubendiamide, but a few populations were less affected by a discriminating rate. F2 screen results of 31 selected FAW populations across regions confirmed that the frequency of diamide resistance alleles remained rather stable. Two laboratory-selected strains exhibited high resistance ratios against flubendiamide, and cross-resistance to anthranilic diamides. Reciprocal crosses indicated that resistance is autosomal and (incompletely) recessive in both strains. F1 backcrosses suggested monogenic resistance, supported by the identification of an I4734M/K target-site mutation in the ryanodine receptor (RyR). Subsequent genotyping of field-collected samples employing a TaqMan-based allelic discrimination assay, revealed a low frequency of RyR I4790M/K mutations significantly correlated with phenotypic diamide resistance. Our findings will help to sustainably employ diamides in FAW resistance management strategies across crops.