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Pathogenicity and repulsion for toxin‐producing bacteria of dominant bacteria on the surface of American pine wood nematodes

Liu, Kan‐Cheng, Zeng, Fei‐Li, Ben, Ai‐Ling, Han, Zheng‐Min
Phytopathologische Zeitschrift 2017 v.165 no.9 pp. 580-588
Delftia, Nematoda, Pinus, Pseudomonas putida, Rhizobium, Stenotrophomonas maltophilia, bacteria, biological control, culture media, microbial culture, nucleotide sequences, pathogenicity, ribosomal DNA, seedlings, sequence analysis, staining, toxicity, vascular wilt, wood, China
Bacteria were isolated from the surface of two samples of American pine wood nematodes to identify methods of controlling pine wilt disease. The dominant bacterial strains were identified, and their toxicity and pathogenicity, in addition to their competitiveness with other pathogenic bacteria, were measured to ascertain how bacteria on the surface of American pine wood nematodes might be used to prevent and control pine wilt disease. The bacterial isolates show that the dominant bacteria carried by the two samples of pine wood nematodes are US4, US5, Smal‐007 and Rrad‐006. Based on routine staining, morphological observation and 16S rDNA sequence analysis, the four strains were identified as Delftia lacustris, Pseudomonas putida, Stenotrophomonas maltophilia and Rhizobium nepotum. The incubation of four dominant bacterial strains and Chinese dominant bacterial strains on the surface of aseptic nematodes and in nutrient broth showed that Smal‐007 and Rrad‐006 have strong competitiveness on the surface of pine wood nematodes. Using a bacterial culture medium to measure the propensity of pine seedlings to wilt, all the American dominant bacterial strains were shown to be less toxic than the Chinese dominant strains. If pine seedlings are inoculated with both bacterial and aseptic pine wood nematodes, American dominant bacterial strains present less pathogenicity than the Chinese dominant bacterial strains. In particular, Smal‐007 and Rrad‐006 show the lowest pathogenicity. If pine seedlings are inoculated with both bacterial and wild pine wood nematodes, American dominant bacterial strains significantly reduce the pathogenicity of wild pine wood nematodes isolated from Zhejiang Province, China. The effects of Smal‐007 and Rrad‐006 are confirmed as the most prominent. The American dominant strains Smal‐007 and Rrad‐006 satisfy two main requirements: excellent repulsion performance and low pathogenicity. Therefore, they can be used as candidate strains for biocontrol bacteria.