Evaluation of mechanisms of azinphos‐methyl resistance in the codling moth Cydia pomonella (L.)

Abstract

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.

Tools for Resistance Monitoring in Oriental Fruit Moth (Lepidoptera: Tortricidae) and First Assessment in Brazilian Populations

“…It is noticeable that the Vacaria population owning the lowest speciÞc AChE activity also was the least susceptible to carbaryl. Similar OP resistance associated to reduced AchEÕs afÞnity for ASCh substrate was described previously in C. pomonella (Reuveny and Cohen 2004). This resistance to chlorpyriphos in oriental fruit moth populations also was associated with an increase of GST and EST (for both ␣-NA and p-NA substrates) activities.…”

Acetylcholinesterase mutation in an insecticide-resistant population of the codling moth Cydia pomonella (L.)

“…In the codling moth, Cydia pomonella L., cross-resistances to different classes of insecticides have been related to enhanced detoxification (Sauphanor et al, 1997;Bouvier et al, 2002), whereas a kdr mutation through leucine to phenylalanine replacement at position 1014 of the voltagedependent sodium channel gene has been identified in pyrethroid resistant populations (Brun-Barale et al, 2005). Organophosphorous (OP) insecticides are the most intensively used against C. pomonella worldwide and resistances to these compounds have frequently been recorded in this species (Welter et al, 1991;Bush et al, 1993;Knight et al, 1994;Sauphanor et al, 1998;Dunley and Welter, 2000;Reuveny and Cohen, 2004). OPs irreversibly inhibit acetylcholinesterase (AChE, EC 3.1.1.7) which is a key enzyme catalysing the hydrolysis of the neurotransmitter acetylcholine in the nervous system, thereby ending transmission of nerve impulses at cholinergic synapses.…”

Molecular Cloning and Expression of CYP9A61: A Chlorpyrifos-Ethyl and Lambda-Cyhalothrin-Inducible Cytochrome P450 cDNA from Cydia pomonella

“…The codling moth Cydia pomonella (L.) (Lepidoptera: Tortricidae) is one of the most serious pests of pome fruits and walnuts in many countries where these crops are cultivated [1–6]. The fruit damages by C. pomonella include boring tunnels to the center of fruit to feed on seeds, contaminating fruits with their frass, and causing fruit abscission.…”