Simultaneous effects of thermal stress and fungal infection on lipid peroxidation and antioxidant system of rice-striped stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae)

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ABSTRACTThe effects of thermal stress, time of exposure, and infection by Beauveria bassiana were determined on the lipid peroxidation and antioxidant system of Chilo suppressalis Walker. The larvae were exposed to 24°C and 34°C for, respectively, 24 h and 72 h. Then, these two groups of larvae were divided into three subgroups: intact larvae, larvae injected with 80 μg/ml of Tween-80 (0.02%), and larvae injected with 104 spores/ml of Beauveria bassiana suspended in 80 μg/ml of Tween-80 (0.02%). The highest activities of superoxide dismutase and peroxidase were found in larvae injected with B. bassiana at both thermal regimes, while the activity of catalase was lowest in these treatments. Highest activities of glutathione S-transferase, glucose-6-phosphate dehydrogenase, and ascorbate peroxidase were observed in the larvae injected with B. bassiana at both thermal regimes. Finally, thermal stress and fungal injection led to the highest amounts of Malondialdehyde and the ratio of oxidized and reduced thiols at both thermal regimes. In our study, the simultaneous exposure of C. suppressalis to thermal stress and B. bassiana infection significantly increased the concentration of oxidative agents in the body of treated larvae, indicating that the antioxidant system may have a role in larval defense.Abbreviations: SOD: Superoxide dismutase; POX: Peroxidase; CAT: Catalase; APOX: Ascorbate peroxidase; GPDH: Glucose-6-Phosphate dehydrogenase; GSTs: Glutathione S-transferases; MDA: Malondialdehyde; RSSR/RSH: Oxidized and reduced thiols.