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Evaluation of mechanisms of azinphos‐methyl resistance in the codling moth Cydia pomonella (L.)
Author(s) -
Reuveny Haim,
Cohen Ephraim
Publication year - 2004
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20016
Subject(s) - codling moth , paraoxon , oxon , chemistry , acetylcholinesterase , carbaryl , carbamate , enzyme , biochemistry , stereochemistry , biology , pesticide , botany , lepidoptera genitalia , neuroscience , agronomy
Resistance of the codling moth Cydia pomonella (L.) to azinphos‐methyl is not based on enhanced detoxifying enzymes like oxidation mediated by mixed function oxidases or by glutathione S‐transferases. Synergism by S,S,S‐tributylphosphoro‐trithioate was evident, but the overall activity of general esterases using p ‐nitrophenyl acetate as the substrate was similar in resistant and susceptible insects. In comparison to acetylcholinesterase (AChE) from susceptible adult codling moth, the enzyme of insects resistant to azinphos‐methyl has low affinities (higher K m values) to the substrates acetylthiocholine (ATCh) and propionylthiocholine. This difference indicates a possible amino acid alteration at the catalytic or anionic binding sites of the resistant enzyme. Inhibition studies revealed no apparent differences in sensitivity of AChE enzymes from resistant and susceptible moths to organophosphorus compounds (OPs), carbamate insecticides and quaternary ammonium ligands. MEPQ (7‐Methylethoxyphosphinyloxy)‐1‐methylquinolinium) is the most powerful OP inhibitor acting at a nM range, while chlopyrifos oxon, azinphos‐methyl oxon and paraoxon are less inhibitory by 22.9, 82.3 and 475 fold, respectively. The codling moth AChE is a typical enzyme that displays substrate inhibition by ATCh, negligible hydrolysis of butyrylthiocholine, very high sensitivity to the bisquaternary ammonium compound BW284c51 and it is not inhibited by the powerful butyrylcholinesterase inhibitor iso‐OMPA. Of the three carbamates examined, only carbaryl was inhibitory at the mM range while pirimicarb and aldicarb were inactive. Of the quaternary ammonium ligands (except for the powerful BW284c51), edrophonium and decamethonium displayed appreciable inhibition rates, while d‐tubocuraine was practically inactive. Arch. Insect Biochem. Physiol. 57:92–100, 2004. © 2004 Wiley‐Liss, Inc.