Plant Growth-promoting and Bio-control Activity of Micrococcus luteus Strain AKAD 3-5 Isolated from the Soybean (Glycine max (L.) Merr.) Rhizosphere

Abstract

Background: Applications of bioinoculants for improving crop productivity may be an eco-friendly alternative to chemical fertilizers. Rhizosphere or soil-inhabiting beneficial microbes can enhance plant growth and productivity through direct and indirect mechanisms, i.e., phosphate solubilization, nutrient acquisition, phytohormone production, etc. Objective: This study is based on the hypothesis that diseases resistant plants can act as a source of potential microbes that can have good plant growth-promoting traits and bio-control potential. Methods: In this study, we have isolated the rhizobacterial strains (AKAD 2-1, AKAD 2-10, AKAD 3-5, AKAD 3-9) from the rhizosphere of a disease-resistant variety of soybean (JS-20-34) (Glycine max (L.) Merr.). These bacterial strains were further screened for various plant growth-promoting traits (phosphate solubilization, indole acetic acid (IAA), ammonia, biofilm, HCN, Exopolysaccharide (EPS), and enzyme production activity (catalase, cellulase, and chitinase)). Results: Among four, only bacterial strain AKAD 3-5 has shown plant-growth-promoting and biocontrol (98%) activity against Fusarium oxysporum. Morphological, biochemical, and molecular characterization (16S rRNA) revealed that this rhizobacterial isolate AKAD 3-5 closely resembles Micrococcus luteus (Gene bank accession: MH304279). Conclusion: Here, we conclude that this strain can be utilized to promote soybean growth under varied soil stress conditions.