Abstract:

For evaluating the insect resistance property of Polygonum orientale L, five extracts of its with petroleum ether, chloroform, ethyl acetate, n-butanol and water were tested for their antifeedant activity against plutella xylostella larvae. The results showed that ethyl acetate extract was the most effective one among the five extracts. In 24h and 48h of treatment, the antifeedant rate of the ethyl acetate extract against 3rd instar larvae of p.xylostella at 5.0mg/mL was 68.42% and 62.55%, respectively. The ethyl acetate extract was further separated through silica gel column and the fractions were monitored with analytical thin layer chromatography (TLC). Thirteen fractions were obtained and also tested for their antifeedant activity against p.xylostella larvae. The bioassay results showed that fraction 8 at 2.5mg/mL had higher antifeedant activity to 3rd instar larvae of p.xylostella than other fractions. The antifeedant rate of fraction 8 was 77.13% in 24h of treatment and 68.53% in 48h of treatment. The inhibiting activity of the 8 fraction against two digestive enzymes glutathion-s-transferase and alkaline phosphatase from the p.xylostella larvae was tested, but carboxylesterase and acid phosphatase were induced.