title: Evidence of multiple/cross resistance to Bt and organophosphate insecticides in Puerto Rico population of the fall armyworm, Spodoptera frugiperda.
abstract: Fall armyworm (FAW) is a damaging pest of many economic crops. Long-term use of chemical control prompted resistance development to many insecticide classes. Many populations were found to be significantly less susceptible to major Bt toxins expressed in transgenic crops. In this study, a FAW strain collected from Puerto Rico (PR) with 7717-fold Cry1F-resistance was examined to determine if it had also developed multiple/cross resistance to non-Bt insecticides. Dose response assays showed that the PR strain developed 19-fold resistance to acephate. Besides having a slightly smaller larval body weight and length, PR also evolved a deep (2.8%) molecular divergence in mitochondrial oxidase subunit II. Further examination of enzyme activities in the midgut of PR larvae exhibited substantial decreases of alkaline phosphatase (ALP), aminopeptidase (APN), 1-NA- and 2-NA-specific esterase, trypsin, and chymotrypsin activities, and significant increases of PNPA-specific esterase and glutathione S-transferase (GST) activities. When enzyme preparations from the whole larval body were examined, all three esterase, GST, trypsin, and chymotrypsin activities were significantly elevated in the PR strain, while ALP and APN activities were not significantly different from those of susceptible strain. Data indicated that multiple/cross resistances may have developed in the PR strain to both Bt toxins and conventional insecticides. Consistently reduced ALP provided evidence to support an ALP-mediated Bt resistance mechanism. Esterases and GSTs may be associated with acephate resistance through elevated metabolic detoxification. Further studies are needed to clarify whether and how esterases, GSTs, and other enzymes (such as P450s) are involved in cross resistance development to Bt and other insecticide classes.
authors.affiliation: USDA-ARS-JWDSRC, Stoneville, MS 38776, USA. Electronic address: yc.zhu@ars.usda.gov.
authors.forename: Yu Cheng
authors.initials: YC
authors.lastname: Zhu
authors.affiliation: USDA, Animal and Plant Health Inspection Service, Biotechnology Regulatory Services, Riverdale, MD 20737, USA.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Blanco
authors.affiliation: USDA-ARS-JWDSRC, Stoneville, MS 38776, USA.
authors.forename: Maribel
authors.initials: M
authors.lastname: Portilla
authors.affiliation: USDA-ARS, Poplarville, MS, USA.
authors.forename: John
authors.initials: J
authors.lastname: Adamczyk
authors.affiliation: USDA-ARS-JWDSRC, Stoneville, MS 38776, USA.
authors.forename: Randall
authors.initials: R
authors.lastname: Luttrell
authors.affiliation: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA.
authors.forename: Fangneng
authors.initials: F
authors.lastname: Huang
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000494:pharmacology*; D001483:Base Sequence; D018432:Drug Resistance, Multiple / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D004731:Endotoxins / Q000235:genetics / Q000494:pharmacology*; D004798:Enzymes / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics / Q000494:pharmacology*; D008658:Inactivation, Metabolic; D019476:Insect Proteins / Q000378:metabolism; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010755:Organophosphates / Q000494:pharmacology*; D009946:Organothiophosphorus Compounds / Q000494:pharmacology; D063088:Phosphoramides / Q000494:pharmacology; D011647:Puerto Rico; D018411:Spodoptera / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D004798:Enzymes; D006460:Hemolysin Proteins; D019476:Insect Proteins; D007306:Insecticides; D010755:Organophosphates; D009946:Organothiophosphorus Compounds; D063088:Phosphoramides; C030956:insecticidal crystal protein, Bacillus Thuringiensis; C001969:acephate; D003576:Electron Transport Complex IV; D005982:Glutathione Transferase; D000469:Alkaline Phosphatase
keywords: Alkaline phosphatase; Esterase; Glutathione S-transferase; Resistance; Spodoptera frugiperda; Trypsin