Biocontrol potential of Pseudomonas fluorescens strains producing 2,4-diacetylphloroglucinol and hydrogen cyanide against tomato Fusarium wilt

Pseudomonas fluorescens strains producing 2,4-diacetylphloroglucinol (DAPG) contribute to the biological control of many fungal plant diseases. Tomato Fusarium wilt is one of the most important diseases of this plant that causes considerable damage to the crop. In the current study, 35 strains of P. fluorescens were screened for the presence of phlD and hcnAB genes and it was revealed that nine strains harbored the target genes. Antagonistic ability of phlD+ and hcnAB닚� was tested against pathogen under in vitro conditions using dual culture method and five strains including PGU, PGU1, PGU2, PGU3 and CHA0 were selected for further studies. Strains were checked for production of antimicrobial metabolites and plant growth promoting traits and then, their potential to control Fusarium wilt and promoting tomato growth was investigated under greenhouse conditions. Laboratory results showed that bacterial strains were capable of producing antimicrobial compounds like DAPG, pyoluteorin and monoacetylphloroglucinol, hydrogen cyanide, indole-3-acetic acid, protease and solubilization of mineral phosphate. Strains were also able to control the disease and stimulate tomato plants growth significantly under greenhouse conditions and PGU strain performed better in comparison to other strains. This study suggests that the production of antimicrobial metabolites and/or metabolites stimulating plant growth plays a key role in effective disease control and increasing plant growth parameters under greenhouse conditions.