Bacillus velezensis BER1 triggered mutualism in the rhizosphere of tomato toward to the suppression of the bacterial wilt

Background: Ralstonia solanacearum is a soil-borne pathogen known for wreaking havoc on crops. Rhizosphere microbiome perform a variety of services that are critical for soil-borne disease prevention. However, it remains unclear how to enhance the positive potential of rhizosphere probiotic microorganisms and how their effects are mediated. The aim of this study was to investigate the ecological mechanism by which biocontrol inoculants regulate rhizosphere flora in enhancing disease inhibition.Results: To disentangle the mechanism of probiotic bacterial inoculants action in the rhizosphere, a growth chamber experiment was conducted to better understand the alterations in the indigenous rhizosphere community associated with tomato cultivated in a bacterial wilt soil, as well as the reactions of rhizosphere microbial populations to an applied probiotic bacterial inoculant. We discovered that probiotics (represented by Bacillus velezensis BER1) changed the microbial composition of bacterial wilt soil and dramatically boosted the abundance of the rhizosphere resident Flavobacterium spp. We also explored the correlation between probiotic inoculants and native Flavobacterium (represented by OUT 438) and disease incidence, as well as the capacity of the two strains to interact to enhance biofilm formation, which may well underlie pathogen suppression. Intriguingly, the two-species consortium also enhanced plant defense responses. This study found that probiotic inoculants can build a plant-beneficial alliance with particular bacterial taxa in the rhizosphere to jointly against the soil-borne pathogen.Conclusion: Our findings imply that disease prevention can be improved indirectly via synergistic interactions between a probiotic bacterial inoculant and a partner species.