Sunday, July 26, 2009
P79

An evaluation on Antifungal activity of Bacillus subtilis against some pathogenic plant fungi

Shadi Selselehzakeri1, Abbas Akhavansepahy1, and Mohammadreza Rezapanah2. (1) Department For Microbiology, Basic Science College, North Tehran Branch, Islamic Azad University, Tehran, Iran, Shariati street, Dastgerdi avenue, Takharestan avenue, Number 23, Floor 4, Tehran, 1918663368, Iran, (2) Biological Control Department, Tehran, Iran, Iran

Bacillus subtilis have the potential to produce antifungal compounds which are placed in iturin group and for this reason they are one of the most important bacteria which could be used in the biological control of pathogenic plant fungi.  In this investigation, a few local and standard isolates of B.subtilis were cultured in Nutrient Broth medium and their antifungal activity vs. Fusarium solani ATCC 11712 and Pythium ultimum ATCC 20692 were evaluated by Agar-well method.  Growth and production of these compounds of the screened bacterium for the factors like carbon and nitrogen sources, were optimized.  The metabolites were extracted and also evaluated in comparison of iturin and surfactin through the High Performance Liquid Chromatography (HPLC).  The antifungal compounds of B.subtilis could inhibit the growth of the both fungi.  Antifungal peptides of iturin group were produced in NB medium with glucose and yeast extract at neutral pH and 30◦C.  Chromatograms of HPLC were revealed the active compounds by identical peaks with the similar retention times as antibiotic compounds belonging to the iturin group.  Antifungal and synergistic effect of iturin A, surfactin and metabolites of B.subtilis were evaluated via Agar-well method. The selected isolate of B.subtilis was the local one which was screened from the soil samples.  The average index of growth suppression of P.ultimum in presence of 50 µl of B.subtilis metabolites, iturin A (1mg/ml), surfactin (1mg/ml) were 20.2, 13.8, 13.4 mm, respectively. This bacterium and its components probably can be suitable candidate for biological control of some pathogenic plant fungi.

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