Phytopathogenic molds cause huge losses in agriculture. Chemical fungicides are mostly used for this purpose, but they present relative high hazard for consumers and the environment. In recent years, however, much research has been devoted in the study of natural antagonistic relationships between bacteria and phytopathogenic fungi. After reviewing this area of reserach, we decided to evaluate potential application of Bacillus spp as antifungal antagonists. We used a direct antagonism assay on potato dextrose agar (PDA) to identiffy a Bacillus strains such as B. siamensis displaying antagonistic activity against several phytopathogenic fungi. It was out aim to evaluate the effect of the liquid culture filtrate of B. siamensis against Aspergillus niger and Botrytis cinerea by adding the filtrate directly to the liquid PDA, where the fungal cultures were cultivated on. We tested influence of cultivation time (48 - 72 hours), glucose concentration (5 - 20 g/L) and culture filtrate concentration (1% - 10%) on fungal cultures growing on PDA. The highest growth inhibition of both B. cinerea and A. niger were detected when B. siamensis was cultivated in low glucose medium (5 g/L) for 48 h. We achieved inhibition of up to 50% of fungal growth. Based on our results, we can conclude that the B. siamensis strain has a good potential as biocontrol agent against several phytopathogenic fungi. Particularly strong effect on growth was observed on the fungus B. cinerea.
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