Biocidal spectrum of a rice field cyanobacterium Nostoc sp.

Abstract

The antimicrobial efficacy of hexane, dichloromethane and ethyl acetate extracts of a rice-field cyanobacterium, Nostoc sp., were evaluated against cyanobacteria and phytopathogenic fungi. The maximum production of biocidal compounds was observed in cultures grown for 20 days under optimized conditions (phosphate =1.4 mg/l; light intensity ≈ 3000-4000 lux). Fractionation of the extracts showed six spots on silica-gel-coated plates. Hexane extract was the most potent biocide, showing marked (35-42%) reduction in the growth of fungi, but no negative influences on seed germination or seedling growth of wheat, rice and mung bean, emphasizing its suitability for use in agriculture.

Keywords: Antifungal; extract; inhibition zone; metabolite; Pythium debaryanum; Rhizoctonia solani