Managing the root rot disease of sunflower with endophytic fluorescent Pseudomonas associated with healthy plants

Use of pesticides is an effective way to control plant diseases but their excessive or misuse of chemical pesticides can cause environmental pollution. Whereas, biological control of plant diseases with saprophytic bacteria and fungi still giving inconsistent results, utilization of endophytic bacteria in plant disease management has been appeared as a new hope. In current study, 40 isolates of endophytic fluorescent Pseudomonas (EFP) were isolated from 20 healthy plants grown in experimental field of Karachi University and agricultural fields of Karachi and its suburb and Identified according to Bergey's manual. Identification of ten potential isolates was also confirmed using genus-specific primer set Le. PA-GS-R F 5'-CACTGGTG1T- CCTTCCTATA-3' and PA-GS-F 5'-GACGGGT-GAGTAATGCCTA-3'. Phylogenetic reconstruction associated the fluorescent Pseudomonas as a descendent of P. monteilii and P. aenginosa. Out of 40 isolates, 10 caused growth inhibition of all 4 test root rotting fungi Macrophomina phaseolina, Rhizoctonia solani, Fusarium solani and F. oxysporum in vitro. Most of them were found to produce hydrogen cyanide, volatile antifungal metabolites, ammonia and indole acetic acid besides solubilizing phosphate. In field plot experiments five selected isolates of EFP were applied as soil drench, significantly suppressed root rotting fungi of sunflower. EFP-121 was found highly effective in improving plant height and fresh shoot weight, than other isolates and carbendazim, a fungicide. Endophytic fluorescent Pseudomonas associated with healthy plants are seems to be an effective alternate to chemical fungicides.