Analysis of secondary metabolites produced by four antifungal bacteria from potato and strawberry plants and their rhizosphere soils

This study was designed out in the framework of evaluating the capacity of growth improvement and protection of plants against biotic and abiotic agents by plant growth-promoting rhizobacteria (PGPR).Accordingly, we evaluated the power of four bacterial isolates that were identified as B6 (Bacillus amyloliquefaciens DMB3), F31 (Acinetobacter lwoffii strain HATC14), Fr43 (Pseudomonas brassicacearum subsp.neoaurantiaca strain IHBB13645), and B29 (Bacillus amyloliquefaciens strain CD2901) in producing specific metabolites, such as siderophores, indole acetic acid (IAA), phosphatases, cellulases, hydrocyanic acid (HCN).The ratio of siderophore production reaches its maximum on the 3rd day of incubation in the four bacterial strains with yellow halo diameter values varying between 1.9 and 2.15.The production of siderophores in the liquid medium is maximal at concentrations of 1 and 20 mmol/l of Fe 3+ with a percentage between 70.8 and 90.64%.This declines at concentrations of 100 and 150 mmol/l in Fe 3+ .The catecholate and hydroxamate siderophores are produced by the three bacterial isolates (Fr43, F31, B29).While strain B6 produces only catecholate.In addition, the Carboxylate siderophore is produced only by strain Fr43.Qualitative production of indole acetic acid was observed in all isolates tested in solid and liquid media.Strains F31, Fr43, B29 and B6 produced 51.21 g/ml, 62.8 g/ml, 77.29 g/ml and 83.09 g/ml of IAA, respectively.In addition, the results show solubilization of Ca 3 (PO 4 ) 2 by the four strains with the presence of a clear halo with a diameter varying between 10 and 16 mm and a quantity between 30.15 g/ml and 82.43 g/ml.The cellulolytic activity of the four isolates Fr43, B6, F31 and B29 showed a halo that reached diameters of 28 mm, 25 mm, 23 mm and 21 mm, respectively.Furthermore, HCN production is illustrated in strains B6 and B29 alone.