Biosurfactants Producing Bacteria as Dual Agents for Plant Growth Promotion and Biocontrol of Pyricularia grisea in Finger Millet under in vitro Condition

Abstract

The present study investigates the potential of biosurfactant producing bacteria isolated from hydrocarbon contaminated soils as dual agents for plant growth promotion and biocontrol of Pyricularia grisea, the causal pathogen of blast disease in finger millet (Eleusine coracana) under in vitro experimental conditions. Enrichment culture techniques yielded sixty-eight bacterial isolates amongst which, five were efficient biosurfactant producers viz., BSB-2, BSB-4, BSB-11, BSB-41 and BSR-51. BSB-2 and BSB-41 demonstrated efficient phosphate (1.55 mg/L, 1.48 mg/L) and potassium solubilization (2.66 mg/L, 2.43 mg/L) indicating strong nutrient-solubilization potential. Antifungal assays using the poison food technique revealed that at 4 mg/mL, BSB-2 (71.28%) showed the highest inhibition of mycelial growth of Pyricularia grisea followed by BSB-41 (70.05%). BSB-2 exhibited the highest biomass reduction of Pyricularia grisea (82.50 %), followed by BSB-41 (78.93%). Elevated levels of β-1,3-glucanase (BSB-2: 4.10 U/mL, BSB-41: 3.75 U/mL) and chitinase activity (BSB-2: 2.87 U/mL) further confirmed their enzymatic role in pathogen degradation. The dual mechanism of biosurfactant combines nutrient solubilization (P, K) with enzymatic (glucanase, chitinase) activities of the isolates resulted in effective fungal suppression and improved nutrient bioavailability, indicating a synergistic mechanism of action. Their multifunctional traits position them as promising bioinoculants for integrated nutrient and disease management in finger millet cultivation. The study emphasizes the potential of biosurfactant producing bacteria as environmentally safe solutions for promoting plant growth and biocontrol agents that enhance soil health, suppress pathogens, boost crop productivity, and strengthen long-term agricultural sustainability.