Antibacterial activity of Iranian Streptomyces coralus strain 63 against Ralstonia solanacearum

Ralstonia solanacearum has worldwide economical importance because of its destructive and soil-borne nature. Clearly chemical measures have lost their attractiveness because of development of resistant strains and undesirable effects on our environment. Consequently, biological control of pathogens is gaining great importance worldwide. To investigate for proper biocontrol agents and to obtain antibacterial antagonists from Iranian soil Actinomycetes, a vast survey was performed. Over 170 isolates of soil Actinomycetes were isolated and screened among which one isolate showed high level of activity in Agar disk and Well diffusion methods against R. solanacearum. It was identified as Streptomyces coralus strain 63. High concentration of antibacterial agent was detected at 8-11th day in shake cultures. Longevity in vitro of the active crude in soluble state determined about 40 days at room temperature. In thermal inactivation point studies, active crude retained activity up to 93°C. Antibacterial activity of the antagonists found in this study highlights their importance as candidates for further investigation in biological control of tested pathogenic bacteria.