Biological control of Sclerotinia sclerotiorum, causal agent of sunflower head and stem rot disease, by use of soil borne Actinomycetes isolates.

Problem statement: High level of biosafety and non adverse effects on the environment of biocontrol strategies of pest management, are priorities of tomorrow's world agriculture. Actinomycetes are active biocontrol agents due to their antagonistic properties against wide range of plant pathogens particularly fungi. Fungal pathogens are liable for a big part of damages in agriculture economy. Approach: In the present research antifungal bioactivity of 50 isolates of Actinomycetes collected from soils of Kerman province of Iran was investigated against Sclerotinia sclerotiorum (Lib.), the causal agent of stem rot in sunflower, through agar disc method and dual culture bioassays. The Streptomyces isolate No. 363 was propagated in submerged cultures and active crude was prepared upon which several biological characterizations performed. Greenhouse studies were achieved to confirm laboratory results. Results: Among the tested Streptomyces isolates, 10 isolates revealed antagonistic properties in dual culture procedure from which isolate No. 363 showed highest bioactivity. The active metabolite of Streptomyces isolate No. 363 was polar and well soluble in H2O. Using agar-disc method, progressive growth of the pathogen was highly reduced by the antagonist through exhibiting ability to constitute fungus-free zones of inhibitions. The results indicated that isolate No. 363 was a proper candidate for field biocontrol studies. Conclusion: Results may open a horizon for production of resistant transgenic plants having antifungal properties originated from biologically active Streptomyces spp. recognition and production of effective metabolite(s) of Streptomyces spp. which was responsible for antifungal activities will be our commercial goal due to rich reserves of soil borne Actinomycetes in Iran.

[1]  S. Aghighi,et al.  First report of antifungal properties of a new strain of Streptomyces plicatus (Strain101) against four Iranian phytopathogenic isolates of Verticillium dahliae, a new horizon in biocontrol agents , 2004 .

[2]  J. Steadman,et al.  A Semi-Selective Medium for Isolation of Sclerotinia Sclerotiorum , 1994 .

[3]  Ralf Thiericke,et al.  Drug Discovery from Nature , 2000 .

[4]  H. Malkawi,et al.  Isolation, identification and analysis of antibacterial activity of soil streptomycetes isolates from north Jordan. , 1999, Microbios.

[5]  I. Saadoun,et al.  Biological Control of Sclerotinia sclerotiorum Using Indigenous Chitinolytic Actinomycetes in Jordan , 2006 .

[6]  T. Kieser.  Practical streptomyces genetics , 2000 .

[7]  G.E.St.J. Hardy,et al.  Biological control of Sclerotinia minor using a chitinolytic bacterium and actinomycetes , 2000 .

[8]  J. Sinclair,et al.  Basic plant pathology methods , 1985 .

[9]  C. Yang,et al.  Generation of PCR-based DNA fragments for specific detection of Streptomyces saraceticus N45. , 2001, Proceedings of the National Science Council, Republic of China. Part B, Life sciences.

[10]  C. Selitrennikoff.  Antifungal Proteins , 2001, Applied and Environmental Microbiology.

[11]  N. Nawani,et al.  Production Dynamics and Characterization of Chitinolytic System of Streptomyces sp. NK1057, a Well Equipped Chitin Degrader , 2004 .

[12]  G. Bonjar.  New Approaches in Screening for Antibacterials in Plants , 2004 .

[13]  D. Gottlieb.  General consideration and implications of the Actinomycetales. , 1973, Society for Applied Bacteriology symposium series.

[14]  G. S. Bonjar,et al.  Broadspectrim, a novel antibacterial from Streptomyces sp. , 2004 .

[15]  B. Hwang,et al.  Diversity of antifungal actinomycetes in various vegetative soils of Korea. , 2002, Canadian journal of microbiology.

[16]  R. Gharaibeh,et al.  The Streptomyces flora of Jordan and its' potential as a source of antibiotics active against antibiotic-resistant Gram-negative bacteria , 2002 .