Abstract: To understand the effects of insecticides on the adaption of the whitefly Bemisia tabaci Mediterranean to stress environment, the expression of the heat shock protein gene hsp70 in this whitefly was investigated using real-time quantitative PCR after treatment with LC₂₅, LC₅₀ and LC₇₅ of nitenpyram, chlorpyrifos and beta-cypermethrin, respectively, at different temperatures. The results showed that at the lower temperature (15℃) the treatments of the three insecticides at LC₅₀ and LC₇₅ for 24 h significantly induced an increase in the expression level of hsp70, and then the expression was decreased gradually and showed no difference from the untreated control at 72 h after treatment; the three insecticides at LC₂₅, however, showed no effect on the expression of hsp70. At room temperature (25℃), nitenpyram, chlorpyrifos and beta-cypermethrin at LC₅₀ and LC₇₅ induced the expression of hsp70 significantly at 24 h after treatment, and then the expression levels were decreased gradually to the normal level at 72 h after treatment; the three insecticides at LC₂₅, however, induced an increased expression of hsp70 with the treatment time. At a higher temperature (32℃), nitenpyram, chlorpyrifos and cypermethrin at LC₂₅ and LC₅₀ significantly induced the expression of hsp70 at 24 h after treatment and the expression levels were then decreased and showed no difference from the control at 72 h after treatment. The high-level expression of hsp70 induced by insecticides enhances the tolerance of the whitefly to insecticides and high temperature, which may be one of the reasons that this whitefly expanded quickly in China.

Key words: Bemisia tabaci Mediterranean, insecticide, heat shock protein, hsp70, mRNA expression level