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Effect of synthetic pyrethroid lambda-cyhalothrin on Helicoverpa armigera glutathione s-transferases

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2004
Konuş, Metin
Helicoverpa armigera is a polyphagous pest. Due to excessive use of insecticides, the field populations of H. armigera have become resistant to synthetic pyrethroids by one or combination of three mechanisms; reduced penetration through the cuticle, decreased nerve sensitivity and enhanced metabolism by the detoxification enzymes especially glutathione S-transferases. In this study, gut sections of H. armigera were obtained from Adana and Antalya field populations and susceptible populations from Israel. Each gut section was homogenized separately in 1.0 ml, 40 mM and pH 7.5 phosphate buffers. GST activity was determined using CDNB as substrate. Product formation linearly increased up to 29.5æg proteins in 20mM, pH 7.5 phosphate buffers. Maximum reaction rate was reached at 30?C. The Vmax and Km values for GST towards CDNB and GSH were calculated with Lineweaver-Burk and Eadie-Scatchard plots as CDNB Vmax; 6.54æmol/min/mg, 6.35æmol/min/mg , Km; 0.29mM, 0.28mM ,respectively and as GSH Vmax; 6.42æmol/min/mg, 6.65æmol/min/mg, Km; 0.22mM, 0.23mM, respectively. Cytosolic GST activity of each individual from Adana, Antalya and susceptible populations were determined under optimized conditions. The mean of GST activity in Adana population (n=50) and Antalya population (n=50) were found 7.824æmol/min/mg and 9.518æmol/min/mg, respectively. The mean of GST activity in susceptible population (n=50) was determined as 3.272æmol/min/mg. According to these results, GST activities of Adana and Antalya field populations̕ showed statistically significant increase (p<0.05) than susceptible H. armigera populations with ANOVA method. In addition, Antalya population showed statistically increase (p<0.05) GST activity than Adana.