Azelaic acid from Pseudomonas nicosulfuronedens MiC45 as an effective compound against Meloidogyne incognita in susceptible pepper.

BACKGROUND: Globally restricted high-toxic chemical nematicides have triggered an urgent demand for ecologically compatible biocontrol alternatives. Antagonistic microbes and their bioactive metabolites serve as eco-friendly candidates to manage Meloidogyne incognita. This study aimed to screen rhizosphere antagonistic bacteria, characterize their primary nematicidal metabolite, and validate their nematicidal efficacy. RESULTS: Strain Pseudomonas nicosulfuronedens MiC45, isolated from the rhizosphere soil of healthy pepper in nematode-infested fields, exhibited potent nematicidal activity, yielding a corrected second-stage juvenile mortality rate of 89.54% at 48 h post-treatment. Liquid chromatography-mass spectrometry (LC-MS) analysis identified azelaic acid as the critical bioactive constituent within its ethyl acetate fermentation extract, with a detected concentration of 505.73 μg/mL. In vitro tests showed that azelaic acid exhibited dose-dependent lethal activity against M. incognita. At 500 μg/mL, the nematodes mortality reached 84.22%, surpassing the positive control abamectin (76.75%). In addition, concentrations ≥ 300 μg/mL greatly suppressed nematode egg hatching, with an inhibition index of 98.71% at 500 μg/mL after 11 days. Moreover, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging revealed cuticle disruption and ultrastructural damage in treated nematodes. Azelaic acid also induced dose-dependent reactive oxygen species (ROS) generation within nematodes. Pot experiments demonstrated that both MiC45 fermentation broth and azelaic acid significantly reduced root gall numbers and nematode invasion, while the fermentation broth simultaneously enhanced pepper biomass. CONCLUSION: Azelaic acid from strain MiC45 suppresses M. incognita by destroying body structures and triggering oxidative stress. These findings provide a theoretical foundation for developing novel biopesticides for pepper production and offer a solid basis for environmentally friendly alternatives to conventional chemical nematicides. © 2026 Society of Chemical Industry.