Biocontrol of tomato soil-borne diseases by fungivorous nematode Aphelenchoides bicaudatus

Crop soil-borne diseases caused by pathogens, such as Fusarium spp. and root-knot nematodes, contribute to substantial yield losses worldwide. This study investigated the biocontrol potential of the fungivorous nematode, Aphelenchoides bicaudatus isolate A23, against soil-borne diseases. Strain A23 showed strong antagonism against phytopathogenic fungi, while remaining non-pathogenic to tomato plants. Among the four soil-borne pathogenic fungi tested, A. bicaudatus exhibited a pronounced feeding preference for Fusarium spp., reducing the incidence of tomato Fusarium wilt by up to 60%. Moreover, in both pot and field trials, A. bicaudatus significantly suppressed root-knot nematode attack reflected in reduced galling index, egg masses, and egg production, thereby increasing fruit yield relative to the control. Split-root assays and qRT-PCR analysis demonstrated that root-knot nematode suppression by A. bicaudatus was primarily mediated by induced systemic resistance, involving the activation of salicylic acid-dependent defense pathways. Additionally, high-throughput amplicon sequencing indicated that A. bicaudatus inoculation reshaped the rhizosphere microbiome by enrichment of beneficial bacterial and fungal genera, while reducing pathogen-associated taxa such as Fusarium. Collectively, these results demonstrated that A. bicaudatus isolate A23 is an effective biocontrol agent that operates through an integrated mechanism combining direct fungal predation, plant defense priming, and beneficial microbiome reshaping. This study establishes a foundation for using fungivorous nematodes in a multifunctional role for crop disease management.