Abstract:

In order to ascertain the insecticidal activity and probe into the insecticidal mechanism of Interruptin B, we studied its biological activity against the 3rd larvae of Plutella xylostella and Ostrinia furnacalis with leaf dipping method and the effect on the number of blood corpuscles in Spodoptera litura larvae by injection and blood cell count, and observed the cell proliferation inhibition of S. litura ovary cells (SL cells) using MTT method. Meanwhile, we observed its effect on the shape, density and the adherence rate of cells by inverted microscope. The results indicated that Interruptin B had the antifeedant and insecticidal activity against the 3rd instar larvae of P. xylostella and O. furnacalis. At 48 h post treatment, the AFC₅₀ values of Interruptin B against the 3rd instar larvae of O. furnacalis and P. xylostella were 108.56 g/mL and 143.88 μg/mL, respectively, while the LC₅₀ values were 346.23 μg/mL and 194.32 μg/mL, respectively. This compound also had strong inhibitive activity on the growth of S. litura larvae, its IC₅₀ values on SL cells at 24 and 48 h post treatment were 13.51 μg/mL and 4.11 μg/mL, respectively. Significant decrease of cell density were observed by microscope in the Interruptin B treated SL cells (P<0.05). The deformation rates of SL cells were 28.18%, 83.90%, 85.18%, 93.93% and 100%, and the adherence rates were 96.59%, 89.90%, 83.18%, 5.06 % and 1.09% at 3, 6, 12, 24 and 48 h post treatment, respectively. The deformation rate and adherence rate of SL cells treated with Interruptin B were significantly different from those in the control at 6-48 h post treatment (P<0.05）. The results show that Interruptin B possesses the antifeedant and insecticidal activity against P. xylostella and O. furnacalis, and can decrease the blood cells of the larvae of S. litura and the density of SL cells, and has strong inhibitive activity on the growth of S. litura larvae. In addition, it can inhibit cell proliferation, change the cell shape, and decrease the adherence rate of SL cells. These suggest that the insecticidal activity of Interruptin B is realized by affecting the cell activity of insects.

Key words: Plutella xylostella, Ostrinia furnacalis, Interruptin B, antifeedant activity, insecticidal activity, Spodoptera litura ovary cells (SL cells)