title: Correlation between fenvalerate resistance and cytochrome P450-mediated O-demethylation activity in Helicoverpa armigera (Lepidoptera: Noctuidae).
abstract: Cytochrome P450 monooxygenases are a major metabolic mechanism responsible for pyrethroid resistance in Helicoverpa armigera (Hübner) from Asia. Cytochrome P450-mediated O-demethylation activity toward p-nitroanisole (PNOD) of individual fourth instars was determined in five strains of H. armigera by using a microplate reader. The four resistant strains of YS, HD, YGF, and YG59 had 6-, 71-, 2540-, and 11,800-fold resistance, respectively, to fenvalerate in comparison with the susceptible BK77 strain. Their mean PNOD activity was 4-, 10-, 24-, and 60-fold, respectively, compared with the BK77 strain. A strong positive correlation (correlation coefficient r = 0.98) between PNOD activity and fenvalerate resistance was found. Of 48 larvae from each strain, only 4% larvae of the susceptible BK77 strain had detectable PNOD activity, whereas 25, 33, 79, and 96% of larvae from the resistant strains YS, HD, YGF, and YG59 exhibited PNOD activity, respectively. There was a clear discrimination of patterns of PNOD frequency distribution between H. armigera strains and their magnitudes of fenvalerate resistance. The PNOD activity can be used as a biochemical marker for monooxygenase-mediated pyrethroid resistance in field populations of H. armigera.
authors: Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
authors: Song
authors: S
authors: Chen
authors: Yihua
authors: Y
authors: Yang
authors: Yidong
authors: Y
authors: Wu
mesh_terms: D000818:Animals; D000840:Anisoles / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007305:Insecticide Resistance; D007306:Insecticides; D007915:Lepidoptera / Q000201:enzymology*; D008745:Methylation; D009570:Nitriles; D011722:Pyrethrins
chemical_list: D000840:Anisoles; D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D003577:Cytochrome P-450 Enzyme System; C005306:4-nitroanisole; C017690:fenvalerate