Point mutations in the voltage-gated sodium channel gene associated with pyrethroid resistance in Iranian populations of the European red mite Panonychus ulmi

• Published in: Pesticide biochemistry and physiology Vol. 157; pp. 80 - 87
• Main Authors: Rameshgar, Fariborz, Khajehali, Jahangir, Nauen, Ralf, Bajda, Sabina, Jonckheere, Wim, Dermauw, Wannes, Van Leeuwen, Thomas
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.06.2019
• Subjects: amino acid substitution; apples; bioassays; copy number variation; enzyme activity; enzymes; fenpropathrin; fenvalerate; Gene duplication; genes; genetic markers; haploidy; Iran; Kdr; males; mites; monitoring; orchards; Panonychus ulmi; pests; point mutation; pyrethrins; Pyrethroids; Resistance; sodium channels; Spider mites; synergism; Tetranychus urticae; toxicity; trees; Voltage-gated sodium channel; Iran; Resistance; Spider mites; Pyrethroids; Kdr; Gene duplication; Voltage-gated sodium channel
• ISSN: 0048-3575; 1095-9939; 1095-9939
• DOI: 10.1016/j.pestbp.2019.03.008

The European red mite Panonychus ulmi (Koch) is a major pest of apple trees worldwide and causes significant damage to apple orchards in Iran. Pyrethroid insecticides/acaricides, such as fenpropathrin and fenvalerate, are widely used to control P. ulmi, but their long-term use may lead to low efficacy. Earlier studies investigating pyrethroid resistance in closely related mites such as Tetranychus urticae revealed that pyrethroid resistance was associated with point mutations in the voltage-gated sodium channel gene (vgsc). The aim of this study was to investigate the biochemical and molecular mechanisms of fenpropathrin and fenvalerate resistance in Iranian populations of P. ulmi. Pyrethroid toxicity bioassays were carried out on different P. ulmi field populations. Marand (resistance ratio, RR = 149), Maraqeh (RR = 90) and Mianeh2 (RR = 71) populations exhibited high levels of resistance to fenpropathrin, compared to a susceptible field population (Shahin Dej). Resistance was also observed for fenvalerate with resistance ratio's ranging from 2- to 20-fold. Synergism experiments and enzyme activity assays predicted a minor role for classical detoxification enzymes. In contrast, two amino acid substitutions in the VGSC, L1024V and F1538I, that were previously shown to confer pyrethroid resistance, were detected in all three resistant P. ulmi populations and point towards target-site insensitivity as the most likely resistance mechanism. Furthermore, sequencing after cloning of vgsc fragments from single haploid males revealed the presence of multiple copies of vgsc in a highly resistant strain. The link between resistance mutations and vgsc copy number variation should be the subject of future study, as this might be used to develop molecular markers for monitoring pyrethroid resistance of P. ulmi in the field. [Display omitted] •Several Iranian populations of P. ulmi were highly resistant to pyrethroids.•Detoxification played a secondary role in resistance to pyrethroids.•L1024V and F1538I mutations of VGSC were detected in resistant populations.•Multiple copies of vgsc gene were found in a resistant population.