Abstract:[Objective] The actinomycete strains with high nematicidal activity against Bursaphelenchus xylophilus were isolated and identified. The virulence factors were determined. [Methods] Strains were selected by plate activity test and insecticidal activity detection by metabolites. Strains were identified by phenotypic and genotypic characteristics. After analyzing the primary characteristics of the activity substances in the fermented broth, the virulence factor was purified and identified using alcohol precipitation, extracted by chloroform, chromatographer, and GC-MS. [Results] Seventy nine actinomycetes were isolated and six strains which had nematicidal activity to B. xylophilus were totally found from the rotten wood, dry branches and fallen leaves in Baotianman Natural Reserves in Nanyang, Henan Province, China. Among which, an actinomycete strain C620, showed the highest nematicidal activity to B. xylophilus. The culture supernatant from the strain C620 separately killed 60.0% and 81.5% of B. xylophilus within 48 h and 60 h, which suggested the high toxic activity toward the nematodes. The actinomycete was classified to be Kitasatospora genus. The virulence factor in the fermented broth of C620 showed strong thermal stability, light stability and storage resistance. The bioactive substance was stable in alkaline environments and can be dissolved in water. Finally, the compound was found to be 1-phenyl-3-(2-pyridyl)-5-pyrazolone. [Conclusion] An actinomycete strain Kitasatospora sp. C620 with high killing activity against B. xylophilus was isolated and the virulence factor was 1-phenyl-3-(2-pyridyl)-5-pyrazolone.
