Biochemical and Antagonistic Profiling of Rhizobacterial Isolates from Mungbean Rhizosphere against Macrophomina phaseolina

Dry root rot, caused by Macrophomina phaseolina, is a devastating soil-borne disease of mungbean (Vigna radiata) leading to severe yield losses in many warm regions. The pathogen produces resilient microsclerotia that can persist in soil and seeds for years, complicating management using crop rotation or chemical fungicides. As an eco-friendly alternative, plant growth-promoting rhizobacteria (PGPR) from the mungbean rhizosphere were investigated for their antagonistic activity against M. phaseolina. In this study, we isolated multiple rhizobacterial strains from mungbean field soils and screened them in vitro for antifungal efficacy using a dual culture assay. The most promising isolates were characterized biochemically and evaluated for traits such as enzyme production, indole-3-acetic acid (IAA) secretion, phosphate solubilization, and hydrogen cyanide (HCN) generation. Results showed that several isolates (especially those identified as Bacillus and Pseudomonas spp.) significantly inhibited M. phaseolina mycelial growth (up to ~60% inhibition) on potato dextrose agar. These antagonistic bacteria also exhibited multiple beneficial traits, including IAA production and phosphate-solubilization, which can promote plant growth. Statistical analysis confirmed the efficacy of the top isolates (p < 0.05). The findings underscore the potential of indigenous mungbean rhizobacteria as biocontrol agents to suppress Dry root rot. Deploying such PGPR in mungbean cultivation could reduce reliance on chemical fungicides and improve disease management in a sustainable manner. Further greenhouse and field trials are warranted to validate the biocontrol and growth-promoting effects of these isolates under natural conditions.