Bioprospecting of aerobic endospore-forming bacteria with biotechnological potential for growth promotion of banana plants

- A funnel-like strategy to bioprospect for PGPR on banana was designed.
- Endospore-forming PGPR strains were detected and selected.
- Growth promotion of banana by Bacillus subtilis EA-CB0575 was dose-dependent.
- Bacterial cells and culture supernatant are active and useful for a bioproduct.

High amounts of agrochemicals are regularly used for increasing yields in cultivation of banana. The use of plant growth-promoting rhizobacteria (PGPR) could represent an environmentally friendly alternative that can improve productivity. In this study, we tested a funnel-like strategy to bioprospect aerobic endospore-forming bacteria (AEFB) that could be useful to develop a biotechnological product to promote the growth of banana plants. First, 837 aerobic endospore-forming bacteria were obtained from the rhizosphere of banana and plantain. Then, the isolates were assessed for both: their capacity to promote growth of maize seedlings (used as a model plant) and to display specific biochemical PGPR-associated traits. Twenty-two of these strains significantly increased the dry weight of maize seedlings, some of them showing in vitro PGPR traits. Based on this screening, four isolates were selected to conduct evaluations on banana plants, from which, the bacterial strain Bacillus subtilis EA-CB0575 was chosen as a promising plant growth-promoting isolate. Further studies with this strain showed that the application of either spores, vegetative cells (both at concentrations 1 × 107 and 1 × 108 CFU/mL), or the cell-free supernatant (CFS) of its fermentation significantly increased the dry weight of banana plants, compared with the non-treated control. Our results suggest that both cellular structures of B. subtilis EA-CB0575 and the metabolites and/or elements contained in its CFS enhance the growth and development of banana plants.