Physiological Optimization and Biocontrol Potential of a Rhizospheric Isolate of Victoriomyces antarcticus Against Cucumber Soil-Borne Pathogens

Driven by the need for sustainable agricultural alternatives to synthetic fungicides, this study investigates the physiological optimization and biocontrol potential of the fungus Victoriomyces antarcticus (isolate AF1), isolated for the first time from the cucumber rhizosphere in Iraq (GenBank: OR131302). Physiological assays revealed that the optimal conditions for mycelial growth were Potato Dextrose Agar (PDA), a temperature of 20°C, pH 6.0, and complete darkness, highlighting its psychrotolerant nature. Antagonistic assays demonstrated significant efficacy against the soil-borne pathogen Rhizoctonia solani, with a maximum growth inhibition rate of 82.22% using the fungal sterile filtrate at a 50% concentration. HPLC analysis identified key bioactive phenolic compounds, predominantly Gallic acid (40.23 µg/ml) and Caffeic acid (22.51 µg/ml), which are likely responsible for the observed antifungal activity. These findings position V. antarcticus as a novel and potent biocontrol agent, offering a viable, eco-friendly strategy for managing root-rot diseases in sustainable cucumber production.