Evaluation of Rhizobacteria and Siderophores-Producing Bacteria from Roots of Selected Leguminous Crops

Abstract

Siderophore production is a potential tool for plant growth promotion and biocontrol. This study evaluated rhizobacteria and siderophore-producing bacteria obtained from roots of leguminous crops. Soil sample were obtained from root regions of common beans (Phaseolus vulgaris L.), peanut (Arachis hypogaea L.), soybeans [Glycine max (L.) Merr.], and cowpea [Vigna unguiculata (L.) Walp.]. Bacterial isolates were identified based on their morphological and biochemical characteristics. Results obtained were compared with those of Bergey's manual of Systematic Bacteriology. All bacteria were screened for ability to produce indole acetic acid (IAA), ammonia, and phosphate solubilisation, using qualitatively methods. Siderophore production and types of siderophore were determined by growing all organisms on enriched Chrome Azurol S (CAS) agar/broth. The findings revealed the presence of twenty-three (23) bacteria belonging to eight (8) genera that include; Bacillus, Corynebacterium, Enterococcus, Micrococcus, Proteus, Pseudomonas, Staphylococcus, and Streptococcus. All bacteria produced IAA except Enterococcus sp. (BPV) while all bacteria produced ammonia except Bacillus sp. (PAH), Bacillus subtilis (CVU), Enterococcus sp. (BPV), and Staphylococcus sp. (PAH). Bacillus subtilis (SGM), Bacillus sp. (PAH), Enterococcus sp (BPV), Proteus sp. (SGM), Staphylococcus saprophyticus (SGM), and Streptococcus (PAH) were among six bacteria that could not solubilize phosphate. Also, most of the organisms were siderophore-producing bacteria with Bacillus and Pseudomonas genera producing the strongest siderophores, which varied from carboxylate, hydroxamate to catecholate-type siderophores. The use of rhizobacteria and siderophore-producing bacteria (SPB) should be encouraged to improve environmentally friendly farming system and ensure food safety.