title: Selection for chlorpyrifos resistance in Liriomyza sativae Blanchard: Cross-resistance patterns, stability and biochemical mechanisms.
abstract: The vegetable leafminer (VLM), Liriomyza sativae (Diptera: Agromyzidae) is a serious pest of vegetable crops and ornamentals worldwide. In cropping systems with inappropriate management strategies, development of resistance to insecticides in leafminers is probable. Chlorpyrifos is a commonly used pesticide for controlling leafminers in Iran, but resistance to this insecticide in leafminers has not been characterized. In order to develop strategies to minimize resistance in the field and greenhouse, a laboratory selected chlorpyrifos resistant strain of L. sativae was used to characterize resistance and determine the rate of development and stability of resistance. Selecting for resistance in the laboratory after 23 generations yielded a chlorpyrifos resistant selected strain (CRSS) with a resistance ratio of 40.34, determined on the larval stage. CRSS exhibited no cross-resistance to other tested insecticides except for diazinon. Synergism and biochemical assays indicated that esterases (EST) had a key role in metabolic resistance to chlorpyrifos, but glutathione S-transferase (GST) and mixed function oxidase (MFO) were not mediators in this resistance. In CRSS acetylcholinesterase (AChE) was more active than the susceptible strain, Sharif (SH). AChE in CRSS was also less sensitive to inhibition by propoxur. The kinetics parameters (Km and Vmax) of AChE indicated that affinities and hydrolyzing efficiencies of this enzyme in CRSS were higher than SH. Susceptibility to chlorpyrifos in L. sativae was re-gained in the absence of insecticide pressure. Synergism, biochemical and cross-resistance assays revealed that overactivity of metabolic enzymes and reduction in target site sensitivity are probably joint factors in chlorpyrifos resistance. An effective insecticide resistance management program is necessary to prevent fast resistance development in crop systems.
authors.affiliation: Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran.
authors.forename: Ghasem
authors.initials: G
authors.lastname: Askari-Saryazdi
authors.affiliation: Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran. Electronic address: mjhejazi@tabrizu.ac.ir.
authors.forename: Mir Jalil
authors.initials: MJ
authors.lastname: Hejazi
authors.affiliation: Atlantic Turf & Ornamental Consulting, 2940 3rd Street SW, Vero Beach, FL 32967, USA.
authors.forename: J Scott
authors.initials: JS
authors.lastname: Ferguson
authors.affiliation: Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mohammad-Reza
authors.initials: MR
authors.lastname: Rashidi
mesh_terms: D000110:Acetylcholinesterase / Q000235:genetics; D000818:Animals; D004390:Chlorpyrifos / Q000633:toxicity*; D004175:Diptera / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides / Q000633:toxicity*
chemical_list: D007306:Insecticides; D000110:Acetylcholinesterase; D004390:Chlorpyrifos
keywords: Acetylcholinesterase; Chlorpyrifos; Cross-resistance; Detoxification; Vegetable leafminer