Evaluation of Bio-Friendly Formulations from Siderophore-Producing Fluorescent Pseudomonas as Biocontrol Agents for the Management of Soil-Borne Fungi, Fusarium oxysporum and Rhizoctonia solani

Secretion of siderophores by Pseudomonas aeruginosa F2 and P . fluorescens JY3 was evaluated on chrome azurol S (CAS) agar plates and their inhibitory effect was inspected against Fusarium oxysporum and Rhizoctonia solani . Production of siderophores as biocontrol agents from F2 and JY3 was accomplished in two optimized media. Afterward, cell-free supernatants of the bacterial cultures containing siderophores were used for the preparation of two bio-friendly formulations for the management of F . oxysporum and R . solani under greenhouse conditions. The investigated bacterial isolates, F2 and JY3, showed antagonistic activity in vitro against F . oxysporum and R . solani and produced siderophores in optimized media with high efficiency. Colonies of both bacterial isolates were grown exponentially with a constant specific growth rate of 0.07 h −1 and 0.27 h −1 , correspondingly. Siderophores estimated in 10 µL reached their highest value of 16.95% at 47 h and 19.5% at 48 h for isolate F2 and JY3, respectively. Formulations of siderophore-generating F2 and JY3 reduced damping-off caused by F . oxysporum by 40% and 80%, while the reduction percentage of damping-off caused by R . solani reached 87.5% and 62.5%, correspondingly. Moreover, both formulations encouraged the growing of wheat plants where the fresh and dry weight of shoots and roots were increased compared to the treatment with each fungus. In conclusion, bio-friendly formulations resulting from this investigation can play an active role in managing soil-borne diseases.