Screening, isolation and mechanism of a nematicidal extract from actinomycetes against the pine wood nematode Bursaphelenchus xylophilus

Actinomycetes are an important microbial resource closely related to human production and life. Approximately 70% of the antibiotics currently used are produced by various actinomycetes. Pine wilt disease (PWD) is caused by the pine wood nematode (PWN) (Bursaphelenchus xylophilus), which is a devastating forest pest that can cause the wilting and death of pine trees. The purpose of this work was to screen out, identify, and ferment active actinomycetes with high lethality to pine wood nematodes and study the active compounds in their secondary metabolites. A group of 227 original strains/isolates of actinomycetes was screened, and Streptomyces sp. TCS19-048 was selected for further analyses. The taxonomic characteristics and molecular analysis results indicated that the strain was a member of the genus Streptomyces and exhibited the highest similarity (99.77%) with the 16S rRNA gene sequences of Streptomyces lactacystinicus OM-6519. Furthermore, the active extract was isolated and had an inhibitory effect on the movement behaviour of B. xylophilus and was able to significantly increase the body fluid leakage of B. xylophilus. This study focused on isolating secondary metabolites from various soil actinomycetes to control PWD and identified an extract with nematicidal activity from a selected strain. The nematicidal effect of extract S-3-1 was confirmed, and the strain Streptomyces sp. TCS19-048 showed good inhibitory activity against B. xylophilus, which was reported for the first time at home and abroad.