Suppression of Macrophomina root rot, Fusarium wilt and growth promotion of some pulses by antagonistic rhizobacteria

The present study aimed to isolate Bacillus and Streptomyces species to control Macrophomina phaseolina and Fusarium oxysporum f. sp. udum that cause root rot and wilt diseases in pulses in general and pigeon pea, respectively. Bacillus subtilis BRBac4-1, B. subtilis BRBac24-2 and Bacillus siamensis BRBac21-1, Streptomyces cavourensis BRAcB10-1 and Streptomyces griseofuscus BRAcB11-2 showed potential antagonistic activity against Macrophomina phaseolina and Fusarium oxysporum f. sp. udum, in a dual culture assay. These rhizobacteria were found to possess multiple plant growth-promoting traits besides producing -lytic enzymes, non-volatile metabolites (iturin and surfactin), and volatile organic carbon compounds (disulphide, azithromycin, 1-butanol, 2-methyl, and dimethyl disulphide) with antifungal activities which were detected in culture filtrate through GC-MS and LC-MS analyses. A pot culture experiment was conducted to test plant growth promotion and disease suppression capacity of the selected rhizobacteria in green gram, black gram, and red gram. In a pot culture experiment, combined inoculation of B. siamensis BRBac21-1 plus S. cavourensis BRAcB10-1 rendered the plant more resistant to fungal infection and further development through the induction of systemic defense in host tissue by improving the status of different defense enzymes (phenylalanine ammonia lyase, polyphenol oxidase, and peroxidase). Furthermore, these two bacteria significantly reduced disease severity, and, promoted shoot and root growth in all the tested crops. In conclusion, B. siamensis BRBac21-1 and S. cavourensis BRAcB10-1 displayed the potential antifungal activities and promoted plant growth and the combined bio-formulation of these two rhizobacteria may be used to manage wilt and root rot pathogens in pulses after field evaluation.