Effect of nitrogen sources on the production of antifungal metabolites by Streptomyces hygroscopicus

Biotechnologically produced antifungal compounds for control of plant diseases caused by phytopathogenic fungi represent a promising alternative to synthetic pesticides. Fungi from the genera Alternaria and Fusarium are listed among important storage pathogens of apple fruits. A. alternata causes significant annual losses of apple fruit. Also, F. avenaceum is one of the most commonly encountered Fusarium species identified as the causal agent of a wet apple core rot. Species of the Streptomyces genera are soil bacteria that produce significant quantities of bioactive compounds in appropriate media. Defining the culture medium composition is the basis of bioprocesses development. Nitrogen source is critical component of cultivation medium and also the most useful tool for stimulation of the antifungal metabolites production. The aim of this study was to select the best nitrogen sources in medium for the production of antifungal compounds effective against A. alternata and F. avenaceum by S. hygroscopicus. Activity of the cultivation liquids on A. alternata and F. avenaceum isolates was tested in vitro using well diffusion method. The results indicate that maximum inhibition zone was reached in medium with soybean meal as nitrogen source with inhibition diameter more than 35 mm for both tested fungi.