Volatile organic compounds produced by Paenibacillus polymyxa J2-4 exhibit toxic activity against Meloidogyne incognita.

Abstract

Root knot nematodes cause great damage to crops worldwide. Due to the negative effects of the application of fumigant and old chemical nematicides, biological nematicides have drawn increasing attention in recent years. Here we tested the fumigant activity of the volatile organic compounds (VOCs) blends emitted from Paenibacillus polymyxa and pure commercial VOCs against M. incognita. In this study, we investigated whether P. polymyxa strain J2-4 could produce VOCs that exhibit nematicidal activity. In vitro assays indicated that J2-4 VOCs were highly toxic to second stage juveniles (J2s) and could inhibit egg hatching. Three-layered pot experiments showed that the number of nematodes that penetrating in cucumber roots was reduced by 69.27% after the application of J2-4 VOCs under greenhouse conditions. We identified 14 volatiles using solid-phase micro-extraction gas chromatography-mass spectrometry. The efficacy of six commercially available VOCs, namely 2-isobutyl-3-methylpyrazine, 2,4-dimethoxybenzaldoxime, 2-dodecanone, 2-tridecanol, 2-tridecanone, and 2-tetradecanol, against M. incognita were examined. Except for 2,4-dimethoxybenzaldoxime, the remaining five VOCs showed strong direct-contact nematicidal activity against J2s of M. incognita, and only 2-isobutyl-3-methylpyrazine showed strong fumigant activity against J2s of M. incognita. In pot experiments, 2-isobutyl-3-methylpyrazine and 2-dodecanone reduced the number of root galls by about 70%, and 2-tridecanone reduced the number of root galls and egg masses by about 63% compared with controls. Paenibacillus polymyxa strain J2-4 exhibited high fumigant activity against M. incognita. Our results provide evidence for the use of J2-4 and its VOCs as biocontrol agents in the management of root-knot nematodes. © 2023 Society of Chemical Industry.