SCREENING OF ACTINOMYCETES FOR ANTIMICROBIAL ACTIVITY AGAINST THE STRAINS OF RALSTONIA SOLANACEARUM (TOMATO BACTERIAL WILT DISEASE)R. JAYASHREEAbstract Actinomycetes constitute the most important group of bacteria, in which Streptomyces having them, high potential in producing secondary metabolites e.g. antibiotics. Actinomycetes play an important role in the rhizosphere region where they influence plant growth and protect plant roots against invasion by pathogenic fungi. Actinomycetes are isolated by taking soil samples from 3 different habitats of Mahe Region of Puducherry Union Territory, India. These samples were serially diluted and plated on actinomycete isolation agar media. Potential colonies were screened and purified. Isolates were morphologically characterized. Antibacterial activity and Minimum Inhibitory Concentration (MIC) of the purified extract of isolates were evaluated. Six actinomycete isolates were observed according to the colour of aerial mycelium from different soils of Mahe region. They are characterized by their tough powdery, pigmented colonies. These were gray, cream, blue, pink, red and white. Among 6 actinomycete, antibiotics produced by one of the Streptomyces isolates had shown activity against Ralstonia solanacearum. Other isolates did not show any antibiosis against any of the test pathogens. The plant pathogen was inhibited by most of the Streptomyces isolates. |