نقش سامانه‌ی دفاعی آنتی‌اکسیدانی در مهار تنش ناشی از کاربرد حشره‌کش‌ها در جمعیت‌های تریپس غربی گل مقاوم به دی‌کلرووس و آبامکتین

Western flower thrips, as one of the dangerous pests of agricultural crops, has a high potential for the development of resistance to insecticides. The high selective pressure of insecticides that leads to resistance to insecticides is a type of stress that can affect the antioxidant defense system and the indicators of oxidative stress. Therefore, in this study, hydrogen peroxide, phenol and malondialdehyde levels were measured as indicators of oxidative stress. In addition, the activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and polyphenol oxidase were measured in the 2nd instar larvae of eight Iranian populations of western flower thrips.
The results showed that the highest content of hydrogen peroxide in the Yazd and Alborz populations, 1.67 and 1.44-fold with a resistance factor 2.114 and 59.57fold, respectively, as compared to the susceptible population. The level of malondialdehyde was also higher in the resistant populations and was evaluated with a ratio of 3.41-fold for Yazd population and 3.16-fold for Alborz population. Unlike the previous two factors, the amount of phenol in the resistant populations was lower than the susceptible one. Also, the results of the measurement of antioxidant defense enzymes activities showed that superoxide dismutase had a higher activity in Yazd and Alborz populations (4.06 and 2.1-fold) and by converting the superoxide anion into hydrogen peroxide, it led to the induction and increase of catalase activity, equal to 2.23 and 1.32-fold, respectively. However, in high concentrations of hydrogen peroxide, this enzyme is gradually saturated and peroxidases such as ascorbate peroxidase and glutathione reductase are activated. The activity of these two enzymes in Yazd and Alborz populations were equal to 1.9 and 1.53-fold and 1.96 and 1.85-fold, respectively. In addition, polyphenol oxidase showed a significant decrease compared to the susceptible population (0.88 and 0.56-fold). Based on the results, it can be noted that in the two resistant populations of western flower thrips, compared to the susceptible one, the harmful effects caused by the presence of a larger content of reactive oxygen species and then hydrogen peroxide are reduced by increasing the activity of enzymes that play a role in the decomposition of these molecules. The antioxidant defense system has kept the population active against the stress caused by the selective pressure of insecticides.