초록
<P>The <I>Bacillus velezensis</I> GJ-7 strain isolated from the rhizosphere soil of <I>Panax notoginseng</I> showed high nematicidal activity and therefore has been considered a biological control agent that could act against the root-knot nematode <I>Meloidogyne hapla</I>. However, little was known about whether the GJ-7 strain could produce volatile organic compounds (VOCs) that were effective in biocontrol against <I>M. hapla</I>. In this study, we evaluated the nematicidal activity of VOCs produced by the fermentation of GJ-7 in three-compartment Petri dishes. The results revealed that the mortality rates of <I>M. hapla</I> J2s were 85% at 24 h and 97.1% at 48 h after treatment with the VOCs produced during GJ-7 fermentation. Subsequently, the VOCs produced by the GJ-7 strain were identified through solid-phase micro-extraction gas chromatography mass spectrometry (SPME-GC/MS). Six characteristic VOCs from the GJ-7 strain fermentation broth were identified, including 3-methyl-1-butanol, 3-methyl-2-pentanone, 5-methyl-2-hexanone, 2-heptanone, 2,5-dimethylpyrazine, and 6-methyl-2-heptanone. The in vitro experimental results from 24-well culture plates showed that the six volatiles had direct-contact nematicidal activity against <I>M. hapla</I> J2s and inhibition activity against egg hatching. In addition, 3-methyl-1-butanol and 2-heptanone showed significant fumigation effects on <I>M. hapla</I> J2s and eggs. Furthermore, all six of the VOCs repelled <I>M. hapla</I> J2 juveniles in 2% water agar Petri plates. The above data suggested that the VOCs of <I>B. velezensis</I> GJ-7 acted against <I>M. hapla</I> through multiple prevention and control modes (including direct-contact nematicidal activity, fumigant activity, and repellent activity), and therefore could be considered as potential biocontrol agents against root-knot nematodes.</P>