Response of Trichogramma brassicae to increasing temperature using molecular and biological methods

The increase in the earth temperature is one of the latest problems threatening the earth ecosystem. Insects as poikilothermic organisms have a high dependence on their environment's temperature so increasing global temperature makes impressions on their distributions, activity, and biological parameters. Trichogramma brassicae (Hymenoptera.: Trichogrammatidae) wasp is one of the most important biological control agents in Iran used to control many species of lepidopterans. In this study, the effect of temperature changes on biological parameters and the expression of two heat shock genes, HSP70 and HSP90, in T. brassicae was studied under laboratory conditions. At first, the main T. brassicae colony was divided into two groups, each of them was separately reared for 20 generations at 30 and 33° C. Then, biological parameters, such as the rate of parasitism, appearance rate, and sex ratio, beside two heat shock gene expressions were assessed. The results indicated that at 33°C, the HSP90 and HSP70 expressions were 2.45 and 1.9 times more than 30°C, respectively, suggesting significant differences at a 99% confidence level. Furthermore, the parasitism rate of T. brassicae at 30 and 33°C were 53.5±2.09 and 40.7±2.14 (from 200 initial eggs), respectively. The obtained results showed that rearing at higher temperature caused to affect the sex ratio, adult appearance rate, and preadult development time. The results of the current study show that increasing global temperature could be result in reducion of the natural enemies efficacy, which will lead to an increase in the probability of pest outbreaks.