Streptomyces rocheiACTA1551, an Indigenous Greek Isolate Studied as a Potential Biocontrol Agent againstFusarium oxysporumf.sp.lycopersici
Many studies have shown that several Greek ecosystems inhabit very interesting bacteria with biotechnological properties. ThereforeStreptomycesisolates from diverse Greek habitats were selected for their antifungal activity against the common phytopathogenic fungusFusarium oxysporum. The isolate encoded ACTA1551, member ofStreptomycesgenus, could strongly suppress the fungal growth when examined in antagonistic bioassaysin vitro. The isolate was found phylogenetically relative toStreptomyces rocheiafter analyzing its 16S rDNA sequence. The influence of different environmental conditions, such as medium composition, temperature, and pH on the expression of the antifungal activity was thoroughly examined.Streptomyces rocheiACTA1551 was able to protect tomato seeds fromF. oxysporuminfectionin vivowhile it was shown to promote the growth of tomato plants when the pathogen was absent. In an initial effort towards the elucidation of the biochemical and physiological nature of ACTA1551 antifungal activity, extracts from solid streptomycete cultures under antagonistic or/and not antagonistic conditions were concentrated and fractionated. The metabolites involved in the antagonistic action of the isolate showed to be more than one and produced independently of the presence of the pathogen. The above observations could support the application ofStreptomyces rocheiACTA1551 as biocontrol agent againstF. oxysporum.