Exploring the bioactive potential of rhizospheric Streptomyces clavuligerus against Macrophomina phaseolina, an incitant of groundnut dry root rot disease

Dry root rot caused by Macrophomina phaseolina is the most destructive soil-borne fungal disease that severely hampers groundnut production. This study investigated the multifaceted biocontrol and plant growth-promoting potential of rhizospheric Streptomyces spp., focusing on the strain Streptomyces clavuligerus GRS-8. In vitro dual culture assays revealed that GRS-8 exhibited the highest antifungal activity, inhibiting 76.50 % of M. phaseolina mycelial growth. The strain also produced key metabolites, including indole-3-acetic acid, siderophores, and hydrolytic enzymes, contributing to plant growth promotion and defense priming. In silico molecular docking identified quininone oxime as a potent bioactive compound with high binding affinity to five virulence-associated proteins of M. phaseolina. Molecular dynamics simulations confirmed the structural stability of the lipase-quininone oxime complex, supporting its potential as a fungal inhibitor. Under protected cultivation, the combined application of GRS-8 liquid formulation via seed treatment, basal application, and soil drenching significantly reduced dry root rot incidence by 73.10 % and enhanced the activity of host defense enzymes. These findings highlight the dualistic mechanism of S. clavuligerus GRS-8 involving direct antifungal action and host defense induction, underscoring its potential as a promising biocontrol agent for sustainable groundnut cultivation.