Nematicidal potential of Bacillus cereus strain NA12 isolated from the rhizosphere of Bergenia ciliata against Meloidogyne incognita

Tomato ( Solanum lycopersicum L.) is an economically important crop in Pakistan, but its yield is often reduced due to infections caused by the root-knot nematode Meloidogyne incognita . Given the environmental and health risks associated with chemical nematicides, there is an increasing need to explore sustainable biological alternatives. This study aimed to isolate and evaluate a nematicidal bacterial strain from the rhizosphere of Bergenia ciliata . Soil samples were cultured on bacterial growth medium, and isolated strains were screened for nematicidal activity using Caenorhabditis elegans as a model organism. Among bacterial isolates, strain NA12 showed approximately 54% nematode mortality on nematode growth medium. In food choice and lawn-leaving assays, nematodes actively avoided bacterial strain NA12, indicating the production of repellent or toxic metabolites. Furthermore, the impact of growth medium on bacterial virulence was also determined; the virulence of NA12 was influenced by the growth medium, with higher activity observed on PGS medium. The bacterial strain was identified as Bacillus cereus through 16S rRNA gene sequencing. For in vivo testing, NA12 was applied to tomato plants via soil drenching, followed by inoculation with Meloidogyne incognita . Treated tomato plants showed significantly reduced root galling and improved growth parameters compared to untreated controls. Importantly, Bacillus cereus NA12 was non-pathogenic to tomato and slightly promoted plant growth, as shown by increased biomass and flower production. These findings suggest that Bacillus cereus NA12 has potential as a biocontrol agent against Meloidogyne incognita . Further research is recommended to elucidate its mode of action and potential for field application.