The College of Medicine, Malawi-Liverpool Wellcome Trust, Clinical Research Programme, Chichiri, Blantyre, Malawi.
Pest Manag Sci. 2011 Aug;67(8):891-7. doi: 10.1002/ps.2145. Epub 2011 Mar 22.
The tomato red spider mite, Tetranychus evansi (Baker and Pritchard), is a serious pest of solanaceous crops in many African countries. In this study an investigation has been conducted to establish whether mutation of the para-type sodium channel underlies pyrethroid resistance in T. evansi strains collected in Southern Malawi.
Two T. evansi strains from Malawi showed tolerance to the organophosphate chlorpyrifos and resistance (20-40-fold) to the pyrethroid bifenthrin, but were susceptible to two contemporary acaricides (abamectin and fenpyroximate) in insecticide bioassays. Cloning of a 3.1 kb fragment (domains IIS5 to IVS5) of the T. evansi para gene from pyrethroid-resistant and pyrethroid-susceptible strains revealed a single non-synonymous mutation in the resistant strains that results in an amino acid substitution (M918T) within the domain II region of the channel. Although novel to mites, this mutation confers high levels of resistance to pyrethroids in several insect species where it has always been associated with another mutation (L1014F). This is the first report of the M918T mutation in the absence of L1014F in any arthropod species. Diagnostic tools were developed that allow sensitive detection of this mutation in individual mites.
This is the first study of pyrethroid resistance in T. evansi and provides contemporary information for resistance management of this pest in Southern Malawi.
番茄红蜘蛛，Tetranychus evansi（贝克和普里查德），是许多非洲国家茄科作物的严重害虫。在这项研究中，进行了一项调查，以确定马拉维南部采集的T. evansi 菌株对拟除虫菊酯的抗性是否源于para 型钠离子通道的突变。
马拉维的两个 T. evansi 菌株对有机磷毒死蜱具有耐受性，对拟除虫菊酯联苯菊酯表现出抗性（20-40 倍），但在杀虫剂生物测定中对两种当代杀螨剂（阿维菌素和氟虫脲）敏感。从对拟除虫菊酯具有抗性和敏感性的菌株中克隆了 3.1 kb 的 T. evansi para 基因片段（域 IIS5 到 IVS5），发现抗性株系中存在一个单一的非同义突变，导致通道域 II 区内的氨基酸取代（M918T）。尽管这种突变在几种昆虫物种中对拟除虫菊酯具有高水平的抗性，但在这些昆虫物种中，它总是与另一个突变（L1014F）相关，而在螨虫中则是新的。这是在任何节肢动物物种中首次报道 M918T 突变而没有 L1014F 的情况。开发了诊断工具，可用于在单个螨虫中灵敏地检测到这种突变。
这是首次对 T. evansi 进行拟除虫菊酯抗性研究，并为马拉维南部控制这种害虫的抗性提供了最新信息。
