Analysis of Molecular Resistance Mechanisms in Helicoverpa armigera (Hübner) (Noctuidae: Lepidoptera) Populations Under Pyrethroid Stress in Turkey
Keywords:Helicoverpa armigera, pyrethroid insecticides, qRT-PCR, CYP450, esterases and glutathione S-transferases
Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a major pest of economically important crops such as cotton, tomato and soybean. In order to control this pest, pyrethroid insecticides have been extensively used in farming areas all over the world. However, applications of excessive amounts of these insecticides can result in resistance development in the field populations of H. armigera. Resistance to the pyrethroids, beta-cypermethrin and lambda cyhalothrin, was analysed using bioassays. It was found that a Ã‡anakkale field population of H. armigera field showed low (2.1-fold) and moderate (14.5-fold) resistance levels for beta-cypermethrin and lambda-cyhalothrin, respectively. Furthermore, expressions of selected CYP450, GST and esterase genes of H. armigera Ã‡anakkale field populations were compared to those of a susceptible strain using real-time PCR. Our results indicate that H. armigera reacts to pyrethroids mainly by increasing expression levels of CYP450s such as CYP9A12 and CYP9A14. However, GST and esterase genes expression levels were not significantly altered in a field population. GSTs and esterases were also analyzed using biochemical assays.Â While GSTs and esterase genes were not found to be up-regulated in the real-time PCR, except GST-DCNB activity, the biochemical assays also showed no significant increases in enzyme activities in the Ã‡anakkale field population as compared to the susceptible strain. Consequently, CYP9A12 and CYP9A14 together with certain GSTs, catalyzing DCNB substrate, are proposed to be involved in the metabolic responses against beta-cypermethrin and lambda-cyhalothrin insecticides in field population of H. armigera from Turkey.
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