| Summary: | The increasing prevalence of crop-threatening root-knot nematodes (RKNs) has stimulated extensive research to discover effective nematicides. A highly focused strategy for accomplishing this is the development of biocontrol agents by a variety of soilborne microorganisms, as different bacterial metabolites have demonstrated promising nematicidal activities. In this study, we characterized the nematicidal and suppressive activity of a bacterial isolate against the agriculturally important RKN <i>Meloidogyne incognita</i> and the model nematode <i>Caenorhabditis elegans</i>, and the main <i>M. incognita</i>-toxic metabolite of the strain. After a preliminary screening of 22 bacterial isolates with a corrected mortality (CM) of whole-cell culture greater than 50% against <i>C. elegans</i> from different RKN-incident soils in China, a total of 14 isolates with CM of the supernatant of culture suspension (SCS) higher than 50% against both <i>M. incognita</i> and <i>C. elegans</i> were rescreened. An isolate with the highest CM of 86.1% and 95.0% for <i>M. incognita</i> and <i>C. elegans</i>, respectively, was further identified as the species <i>Brevundimonas bullata</i> via morphological examination, physiological and biochemical assays and alignment analysis of 16S rRNA gene sequences. The SCS of this strain, namely, <i>B. bullata</i> MB756, exhibited synchronous <i>M. incognita</i> killing activity along with significant detrimental effects on the growth, brood size, and locomotion of <i>C. elegans</i>. The effects of heat treatment, pH, inoculations, and protease K proteolysis on the CM of MB756 SCS were evaluated. A major <i>M. incognita</i>-toxic substance in the MB756 SCS was assayed and identified using thin-layer chromatography, column chromatography and high-performance liquid chromatography with a mass spectrometer, and it was preliminarily identified as 2-ethylhexan-1-ol, with a molecular formula of C<sub>8</sub>H<sub>18</sub>O and a molecular weight of 130.3 Da.
|
|---|