title: Electrical penetration graph technique as a tool to monitor the early stages of aphid resistance to insecticides.
abstract: BACKGROUND
  Sulfoxaflor, a new insecticide from the sulfoximine chemical family, and imidacloprid, a widely used neonicotinoid insecticide, were tested to assess the susceptibility and feeding behaviour of two populations of Myzus persicae: Mp61, which exhibited target-site R81T resistance to neonicotinoids, and Mp1989, a laboratory clone maintained since 1989 as a susceptible reference.
  
  
  RESULTS
  The imidacloprid LC50 value for Mp61 was 16 times higher than for Mp1989, showing a moderate level of resistance. Sulfoxaflor LC50 values for Mp61 and Mp1989 were much closer. The probing behaviour, as assessed by electrical penetration graphs (EPGs), of both populations was clearly altered by sulfoxaflor, which reduced the ability of aphids to find and feed from the phloem. The feeding behaviour of the susceptible Mp1989 population was much more severely affected than the moderately resistant Mp61 population on imidacloprid-treated plants. PCR assays of both aphid populations followed by DNA sequencing identified differences between populations in the point mutation in the β-subunit of the nicotinic acetylcholine receptor linked to the resistant gene against the neonicotinoid insecticide.
  
  
  CONCLUSIONS
  Sulfoxaflor provoked feeding cessation more rapidly than imidacloprid in both aphid populations. Sharp differences in feeding behaviour were detected between the susceptible and the moderately resistant neonicotinoid-resistant aphid populations. The EPG technique can be used as a useful tool to give new insights into the functional effects of new chemical compounds and for early detection of low to moderate levels of resistance of sap-feeding insects to insecticides. The potential of this technique was validated by molecular analysis of the R81T mutation target site.
authors.affiliation: Institute of Agricultural Sciences, ICA, CSIC, Madrid, Spain.
authors.forename: Elisa
authors.initials: E
authors.lastname: Garzo
authors.affiliation: Institute of Agricultural Sciences, ICA, CSIC, Madrid, Spain.
authors.forename: Aranzazu
authors.initials: A
authors.lastname: Moreno
authors.affiliation: Institute of Agricultural Sciences, ICA, CSIC, Madrid, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Hernando
authors.affiliation: Institute of Agricultural Sciences, ICA, CSIC, Madrid, Spain.
authors.forename: Vera
authors.initials: V
authors.lastname: Mariño
authors.affiliation: Dow Agrosciences Iberica S.A., Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Torne
authors.affiliation: Centre for Plant Biotechnology and Genomics, UPM-INIA, Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Estrella
authors.initials: E
authors.lastname: Santamaria
authors.affiliation: Centre for Plant Biotechnology and Genomics, UPM-INIA, Pozuelo de Alarcón, Madrid, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Díaz
authors.affiliation: Institute of Agricultural Sciences, ICA, CSIC, Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Fereres
mesh_terms: D000818:Animals; D001042:Aphids / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D001681:Biological Assay / Q000379:methods*; D004252:DNA Mutational Analysis; D004560:Electricity; D005247:Feeding Behavior / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides / Q000494:pharmacology*; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D013457:Sulfur Compounds / Q000494:pharmacology
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D011725:Pyridines; D013457:Sulfur Compounds; C082359:imidacloprid; C560328:sulfoxaflor
keywords: EPGs; green peach aphid; neonicotinoids; resistance; sulfoximine