Although strain UTB1 is able to degrade aflatoxin, its ability to inhibit fungal growth is not considerable. In the present study, we were interested in improving the antagonistic activity of strain UTB1 against A. flavus R5. Mutagenesis by either physical mutagens (gamma or UV irradiation) or chemical mutagens is used as a tool for improvement in potentiality of biocontrol agents and/or antifungal metabolites producers