Biological Impact and Enzyme Activities of Spodoptera litura (Lepidoptera: Noctuidae) in Response to Synergistic Action of Matrine and Beauveria brongniartii

Abstract

Matrine, a naturally occurring heterocyclic compound, has been shown to enhance the pathogenicity of the entomopathogenic fungus Beauveria brongniartii against Spodoptera litura. In the current study, the biological impacts and synergism activities of these two agents on nutritional efficiency and antioxidant enzymes in S. litura were explored. Our results showed a high antifeedant activity of B. brongniartii and matrine on S. litura. The S. litura larvae were unable to pupate and emerge when treated with combinations of matrine and B. brongniartii. Following on, we measured the activities of five important antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), acetylcholinesterase (AChE), and glutathione-S-transferase (GST)] when treated with B. brongniartii SB010 (1 × 10⁹ spores/ml), matrine (0.5 mg/ml), and B. brongniartii SB010 (1 × 10⁹ spores/ml) + matrine (0.5 mg/ml). The results indicated the detoxification activity of the five enzymes in the fat body and hemolymph of S. litura when facing a combined B. brongniartii and matrine challenge. The activities of the enzymes were significantly lower than that of the control group 7 days post-treatment, indicating the inhibitory effect of the two xenobiotics. Matrine had better inhibition effects than B. brongniartii in a majority of the trials. The improved detoxification activity of the five enzymes may be the internal mechanism of synergism of matrine on B. brongniartii.

Keywords: Beauveria brongniartii; Spodoptera litura; antioxidant enzymes; matrine; nutritional efficiency.

Figure 1

Effect of Beauveria brongniartii and matrine on the pupation rate of Spodoptera litura. Bars having different letters show significant differences between treatments. T1 = Control; T2 = Matrine 0.5 mg/L; T3 = Matrine 1.0 mg/L; T4 = B. brongniartii 1 × 10⁸ conidia/ml; T5 = B. brongniartii 1 × 10⁸ conidia/ml; T6 = B. brongniartii11 1 × 10⁸ conidia/ml + Matrine 0.5 mg/L; T7 = T6 = B. brongniartii 1 × 10⁸ conidia/ml + Matrine 1.0 mg/L; T8 = B. brongniartii 1 × 10⁹ conidia/ml + Matrine 0.5 mg/L; and T9 = B. brongniartii 1 × 10⁹ conidia/ml + Matrine 1.0 mg/L.

Figure 2

Effect of Beauveria brongniartii and matrine on the emergence rate of Spodoptera litura. Bars having different letters show significant differences between treatments. T1 = Control; T2 = Matrine 0.5 mg/L; T3 = Matrine 1.0 mg/L; T4 = B. brongniartii 1 × 10⁸ conidia/ml; T5 = B. brongniartii 1 × 10⁸ conidia/ml; T6 = B. brongniartii 1 × 10⁸ conidia/ml + Matrine 0.5 mg/L; T7 = B. brongniartii 1 × 10⁸ conidia/ml + Matrine 1.0 mg/L; T8 = B. brongniartii 1 × 10⁹ conidia/ml + Matrine 0.5 mg/L; and T9 = B. brongniartii 1 × 10⁹ conidia/ml + Matrine 1.0 mg/L.

Figure 3

Changes in glutathione-S-transferase (GST) activity of Spodoptera litura following treatment with Beauveria brongniartii and matrine (A) in the fat body and (B) in hemolymph. Bars having different letters show significant differences between treatments at different time intervals.

Figure 4

Changes in acetylcholinesterase (AChE) activity of Spodoptera litura after treatment with Beauveria brongniartii and matrine (A) in the fat body and (B) in hemolymph. Bars having different letters show significant differences between treatments at different time intervals.

Figure 5

Changes in superoxide dismutase (SOD) activity of Spodoptera litura after treatment with Beauveria brongniartii and matrine (A) in the fat body and (B) in hemolymph. Bars having different letters show significant differences between treatments at different time intervals.

Figure 6

Changes in catalase (CAT) activity of Spodoptera litura following treatment with Beauveria brongniartii and matrine (A) in the fat body and (B) in hemolymph. Bars having different letters show significant differences between treatments at different time intervals.

Figure 7

Changes in peroxidase (POD) activity of Spodoptera litura following treatment with Beauveria brongniartii and matrine (A) in the fat body and (B) in hemolymph. Bars having different letters show significant differences between treatments at different time intervals.