Abstract
This study aims to increase Bacillus and Streptomyces antagonistic activity against the root rot and wilt diseases of pulses caused by Macrophomina phaseolina and Fusarium oxysporum f. sp. udum, respectively. To increase antagonistic action, Bacillus subtilis BRBac4, Bacillus siamensis BRBac21, and Streptomyces cavourensis BRAcB10 were subjected to random mutagenesis using varying doses of gamma irradiation (0.5-3.0 kGy). Following the irradiation, 250 bacterial colonies were chosen at random for each antagonistic strain and their effects against pathogens were evaluated in a plate assay. The ERIC, BOX, and random amplified polymorphic studies demonstrated a clear distinction between mutant and wild-type strains. When mutants were compared to wild-type strains, they showed improved plant growth-promoting characteristics and hydrolytic enzyme activity. The disease suppression potential of the selected mutants, B. subtilis BRBac4-M6, B. siamensisi BRBac21-M10, and S. cavourensis BRAcB10-M2, was tested in green gram, black gram, and red gram. The combined inoculation of B. siamensis BRBac21-M10 and S. cavourensis BRAcB10-M2 reduced the incidence of root rot and wilt disease. The same treatment also increased the activity of the defensive enzymes peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. These findings suggested that gamma-induced mutation can be exploited effectively to improve the biocontrol characteristics of Bacillus and Streptomyces. Following the field testing, a combined bio-formulation of these two bacteria may be utilised to address wilt and root-rot pathogens in pulses.
Highlights
The same treatment increased the activity of the defensive enzymes peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. These findings suggested that gamma-induced mutation can be exploited effectively to improve the biocontrol characteristics of Bacillus and Streptomyces
F. oxysporum sp. udum was inhibited by B. siamensis BRBac 21-M15 to a maximum of 56%
Mutant Bacillus and Streptomyces strains displayed significantly better antagonistic activity against M. phaseolina and F. oxysporum f. sp. udum compared with wild-type bacteria, owing to increased synthesis of lipopeptides, hydrolytic enzymes, and swarming and swimming motilities
Summary
Pulses are India’s most important protein dietary source, with minimal fat and high fibre and nutrient content [1]. India cultivates roughly 34% of the worldwide cultivable land for pulses and contributes 24% of the global pulses production [2]. Productivity of pulses in India is extremely low (652 kg ha−1) (FAOStat, 2013). It is estimated that wilt and rot diseases cause 40–45% of the yield loss in pulses [3,4]. Udum and Macrophomina phaseolina are the primary pathogens responsible for wilt and root rot diseases in pulses, respectively. Traditional methods for controlling soil-borne fungal infections include fungicide treatment, This work is licensed under the Creative Commons Attribution 4.0
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