Isolation and identification of Bacillus velezensis RTS-M11 and assessment of its antifungal activity

The selection of putative antagonists for the biological control of plant diseases usually involves collecting and screening large numbers of microbial isolates so as to increase the probability of discovering highly effective strains. Different strains of Bacillus velezensis produce secondary antifungal metabolites that could control plant diseases. The ability to form spores makes this bacterium an ideal candidate for biological control. Isolation, characterization, and identification of B. velezensis (native to Iran) from soil and its antifungal activity against Fusarium sp. have been reported in the present study. Eight out of 75 isolates showed antifungal activity against three main species of Fusarium under standard conditions. The morphological and biochemical characteristics, along with the 16S rRNA and gyrB genes sequences of the selected isolate, indicated that it belongs to the B. velezensis species. The results showed that sucrose as a carbon source and peptone as a nitrogen source in a culture medium at pH 7 and an agitation speed of 200 rpm led to the maximal growth rate and antifungal activity in the B. velezensis sp.RTS-M11 selected strain. This isolate seems potentially useful as a biological agent against a few Fusarium sp. but needs more study in the future.