Isolation, Characterization of Streptomyces aquilus from Agricultural Soil and its Antifungal Activity Against Rhizoctonia solani

Abstract

Streptomyces, a genus of Actinomycetes that is renowned for the production of various bioactive compounds especially antifungal compounds against phytopathogens. Rhizoctonia solani is a devastating soil-borne fungal pathogen responsible for significant yield losses in potato and several other crops. The current research aimed at the isolation and characterization of Streptomyces strains from agricultural soils and the assessment of their antifungal activity against R. solani. Nine rhizospheric soil samples collected from different agricultural crop fields yielded a total of eighteen Actinomycetes isolates. Primary screening against Rhizoctonia solani identified seven isolates with antagonistic activity. Secondary screening using crude ethyl acetate extracts revealed that isolates W1 (wheat soil isolate) and R1 (rice soil isolate) exhibited the strongest antifungal activity. The antifungal potential of the selected isolates was further evaluated through agar well diffusion, concentration-dependent growth inhibition assay, and fungicidal activity assessment. Isolates W1 and R1 had the highest zones of inhibition. Antifungal potential of the isolates was also measured by finding Concentration-dependent inhibition and Minimum Fungicidal Concentration (MFC) with the isolate W1 exhibiting the best antifungal activity. The isolate W1 was identified as Streptomyces aquilus by molecular identification via 16S rRNA gene sequencing method. The findings concluded that S. aquilus has great prospects of being a biocontrol agent to control the R. solani induced diseases in potato. This study identifies a sustainable and environmentally friendly way of managing plant diseases by utilizing the resources of soils in the form of microbes.