Protorhabditis nematodes and pathogen-antagonistic bacteria interactively promote plant health

Abstract

Abstract Background Fertilization practices control bacterial wilt-causing Ralstonia solanacearum by shaping the soil microbiome. This microbiome is the start of food webs, in which nematodes act as major microbiome predators. However, the multitrophic links between nematodes and the performance of R. solanacearum and plant health, and how these links are affected by fertilization practices, remain unknown. Results Here, we performed a field experiment under no-, chemical-, and bio-organic-fertilization regimes to investigate the potential role of nematodes in suppressing tomato bacterial wilt. We found that bio-organic fertilizers changed nematode community composition and increased abundances of bacterivorous nematodes (e.g., Protorhabditis spp.). We also observed that pathogen-antagonistic bacteria, such as Bacillus spp., positively correlated with abundances of bacterivorous nematodes. In subsequent laboratory and greenhouse experiments, we demonstrated that bacterivorous nematodes preferentially preyed on non-pathogen-antagonistic bacteria over Bacillus. These changes increased the performance of pathogen-antagonistic bacteria that subsequently suppressed R. solanacearum. Conclusions Overall, bacterivorous nematodes can reduce the abundance of plant pathogens, which might provide a novel protection strategy to promote plant health. Video Abstract

Keywords

• Bio-organic fertilization
• Ralstonia solanacearum
• Bacterivorous nematode selective predation
• Pathogen-suppressing Bacillus spp
• Nematode-bacteria trophic interaction