Bacillus subtilis EA-CB0575 inoculation of micropropagated banana plants suppresses black Sigatoka and induces changes in the root microbiome

Purpose: Root inoculation of plants with beneficial microorganisms promotes plant growth and improves tolerance to biotic and abiotic stresses. In banana plants, microbial inoculation has shown promising effects on plant growth, but the effect on foliar diseases and on the resident native microbial community is yet unknown. We examined the effects of Bacillus subtilis EA-CB0575 introduced on roots of micropropagated banana plants on black Sigatoka disease and on the root microbiome. Methods: In vitro banana seedlings were root-inoculated with strain EA-CB0575, and then treated with the foliar pathogen Pseudocercospora fijiensis. Root bacterial communities were characterized using 16S rRNA gene sequencing, before and after pathogen inoculation; and the severity of the disease was determined. Results: Inoculation of strain EA-CB0575 on in vitro banana roots provided a reduction in the severity of black Sigatoka disease in greenhouse. This inoculation induced changes in the composition of the bacterial root microbiome, changes that arose from amplicon sequence variants (ASVs) of low abundances. Differential abundance analysis of ASV indicated that prior pathogen inoculation significantly more enriched sequences were identified in roots treated with EA-CB0575 (191-ASVs) compared to control plants (73-ASVs), but after pathogen inoculation more sequences were found in control (277-ASVs) than bacterial inoculated plants (60-ASVs). Furthermore, in vitro banana roots host a bacterial community that differ from that of greenhouse plants. Conclusion: Results suggest that banana plants inoculated with B. subtilis EA-CB0575, reshape the composition of the bacterial community in a P. fijiensis dependent manner and induce systemic resistance protecting plants against black Sigatoka.