Analysis of the activity and biological control efficacy of the Bacillus subtilis strain Bs-1 against Meloidogyne incognita

Abstract

Root-knot nematodes are severe soil-borne pathogens that cause great damage to vegetable crops and economic losses all over the world annually. Therefore, there is an urgent need to seek novel nematicides or biological control agents. In this study, a bacterium strain, the Bacillus subtilis strain Bs-1, was obtained from rhizospheric soil, and had strong nematicidal effects and caused egg hatching inhibition and repellence of Meloidogyne incognita. Nematicidal activity was evaluated according to fermentation assays, and the mortality rate of second-stage juveniles (J2s) to the Bs-1 fermentation treatment was 100%. The results of ovicidal experiments indicated that fermentation of the strain Bs-1 also had a strong effect on decreasing the egg hatching rate. In both pot and field experiments, Bs-1 fermentation was able to significantly reduce root galls and promote the growth of cucumber. A repellence test of Bs-1 fermentation showed that a majority of J2s were obviously repelled by the Bs-1 fermentation and supernatant, but were attracted by cucumber root extracts. The gas chromatography-mass spectrometry (GC-MS) results showed that the volatile organic components (VOCs) produced by the strain Bs-1 were complex and diverse, such as ketones, acids, alkyls, sulfide and heterocyclic compounds and so on. These results revealed that the B. subtilis strain Bs-1 provides strong suppression against M. incognita and could be used as a potential biological control agent to suppress M. incognita.