BIOCONTROL OF FUSARIUM OXYSPORUM IN UNSTERILIZED SOIL BY NOVEL STREPTOMYCES CACAOI SUBSP CACAOI [M20]

Abstract

Objective: To find bio fungicide from mangrove actinomycetes for controlling seed and soil borne pathogen-Fusarium oxysporum. Methods: A total of 25 actinomycetes were isolated by pour plate method. These were screened for fungicidal activity by agar plug method. The isolate M20 was characterised further for identification. The phytotoxicity study was done; biocontrol of Fusarium oxysporum with 10% culture filtrate was done using food poisoning technique. Volatile toxicity of isolate M20 was studied by inverted plate technique. The methanolic crude extract was subjected for UV–Vis spectral analysis for identifying the group of compound present.Results: The isolated M20 found to be better in antifungal activity. 10% culture filtrate actively inhibited the growth of Fusarium oxysporum (77.7%), 10% culture filtrate was taken as a standard concentration for biocontrol of Fusarium oxysporum using green gram as the test plants. The 15th-day green gram plants under treatment with the antagonist (A), antagonist+pathogen (A+P), antagonist+pathogen+rhizobium (A+P+R) yielded high biomass and better growth. The disease development by the pathogen in green gram was controlled by the antagonist. The compounds (pyrimidine nucleosides-neutral and acidic polyoxins (230 nm), (270-290 nm) and heptaene antifungal antibiotics (406-417 nm)) are preliminarily confirmed from the methanolic crude extract of the isolate M20-Streptomyces cacaoi subsp cacaoi.Conclusion: Since the isolate M20 controlled the growth and disease causing potentiality of Fusarium oxysporum, it can be effectively used to control seed and soil borne diseases that are caused by Fusarium oxysporum.