Multi-cycle application of Virgibacillus dokdonensis induces a root-knot nematode-suppressive soil via specifically recruiting functional Pseudomonas

INTRODUCTION: Inducing the development of disease-suppressive soils against root-knot nematodes (RKNs) represents a sustainable strategy for reducing pesticide dependence, with microbial management serving as a core approach. However, the formation mechanisms, key microbial drivers, and functional stability of RKN disease suppressive soil remain poorly understood. OBJECTIVES: This study aimed to elucidate the ecological mechanisms underlying soil microbiome-mediated suppressiveness against RKNs induced by multi-cycle application of the deep-sea biocontrol bacterium Virgibacillus dokdonensis MCCC 1A00493. METHODS: Using a three-cycle consecutive microcosm experiment, we tracked RKN disease incidence and soil microbial community dynamics. We combined microbiome sequencing with functional assays to identify key functional taxa, and constructed synthetic microbial communities (SynComs) to validate their synergistic suppression with V. dokdonensis. RESULTS: Continuous application of V. dokdonensis significantly reduced RKN disease, with the control efficacy reaching 37.86%, 51.11%, and 65.85% over three cropping cycles. This suppressiveness was achieved through direct antagonism and the reshaping of the soil bacterial community, which involved the successful colonization of V. dokdonensis and specific enrichment of indigenous functional Pseudomonas. Metagenomic analysis indicated a significant upregulation of bacterial chemotaxis genes. Further chemotaxis assays confirmed that the fermentation supernatant of V. dokdonensis specifically attracts high-nematicidal Pseudomonas, achieving a relative chemotaxis index reaching 3.0 to 9.1. Based on this, we constructed synthetic communities of functional Pseudomonas with varying complexity levels. Among them, a simplified SynComV1, consisting of Pseudomonas monteilii, P. parafulva, P. fulva, P. plecoglossicida, and P. putida, exhibited the greatest disease suppression, reaching 48.38%. Notably, co-application of V. dokdonensis and SynComV1 demonstrated significant synergistic effects, enhancing the control efficacy to 58.33%. CONCLUSIONS: Overall, this study revealed that multi-cycle application of V. dokdonensis induces a RKN-suppressive soil by specifically recruiting indigenous high-nematicidal Pseudomonas to synergistically suppress RKN disease. These findings provide a practical strategy for developing efficient and sustainable technologies for RKN management.