Bacillus subtilis Strains Isolated from Cocoa Trees (Theobroma cacao L.) Rhizosphere for their use as Potential Plant Growth Promoting Rhizobacteria in Côte d'Ivoire.

Abstract

Plant growth promoting rhizobacteria (PGPR) are important for agriculture through their activity in stimulating and facilitating plant growth. The rhizobacteria were screened for molecular characterization and followed by their indole acetic acid (IAA) production, phosphate solubility, antibiosis activity. In this study, 162 soil samples were collected from the cocoa rhizosphere to isolate Bacillus subtilis strains using Mössel agar medium with an additional egg yolk and identified by sequencing the ytcP gene. The ability of each strain to form biofilms was obtained in a tube. Indole-3-acetic acid (IAA) production was estimated in Yeast Peptone Dextrose (YPB) broth. Phosphates were solubilized by each strain on Pikovskaya agar medium. The detection of lipopeptide genes using the molecular method has established the possession of isolates by antimicrobial genes. Fifty (50) B. subtilis strains were isolated and identified using the ytcP gene. Ninety percent (90%) of the strains were able to form a biofilm. All isolates produced an IAA. Forty (40 (80%)) of B. subtilis were solubilized phosphate with phosphate solubilizing index (PSI) of 0 to 97.33 ± 0.70%. Of all B. subtilis strains, 45 (90%) have the srfAA gene, 19 (38%) have the fenD gene and 12 (24%) have the ituC gene. B. subtilis strains from cocoa rhizosphere would be beneficial for agricultural production by their PGPR activities.