Antagonistic Activity of Streptomyces olivaceus against Rhizoctonia solani

Biological control offers an environmentally friendly alternative to the use of chemical pesticides for controlling plant diseases. Biological activity of Iranian (Streptomyces olivaceus strain 115) against (Rhizoctonia solani Kuhn AG-3, Teleomorph: Thanatephorus cucumeris [(Frank) Donk]) was investigated. A collection of about 200 Actinomycete isolates was screened for the ability to produce metabolites that inhibit (R. solani) growth in vitro and in vivo. The (Streptomyces olivaceus strain 115) showed strong in vitro antagonistic activity against (R. solani) in Agar disk, Well- diffusion ad Dual culture methods by producing extra cellular antifungal metabolites. This strain was propagated in submerged cultures and active crude was prepared upon which some biological characterization performed. The active metabolite was polar, soluble in H2O and methanol but insoluble in chloroform, dichloromethane and hexane. Thermal inactivation point of active phase was 80°C. MIC of the crude was determined as 2.5 mg/ml against (R. solani). Stability of the active crude in DM solvent and dry form persisted one month at 15° C and three months at 25° C respectively. Antifungal activity was persistent in 6- 9 range of pH. Antifungal gene from (S. olivaceus strain 115) is a useful candidate for genetic engineering of agriculturally important crops for increased tolerance against (R. solani) and similar phytopathogens.

کلیدواژه ها:

Antifungal ، Biological control ، Actinomycetes ، Streptomyces olivaceus ، Rhizoctonia solani ، Bioassay ، Thermal Inactivation Point