Identification of fluorescent pseudomonads isolated from potato Rhizospher and assessment of their antagonistic activity towards Pectobacterium carotovorum under field condition

Potato rhizospher soil and tubers were collected from Hamadan, Damavand and Qasere-Shrin areas. A total of 96 Fluorescent Pseudomonads strains from collected soil and tuber samples were isolated on pseudomonas agar F medium. Based on the antagonistic activity of the fleuoresent pseudomonads strains against Pectobacterium carotovoru invitro, 40 representatives were selected and their phenotypic features were characterized. Phenotypic feature characterizations resulted three species including Pseudomonas aeruginosa, P. Putida and P. fluorescens (bv. II, III & IV). Antagonistic activity assessment of 20 representative's strains of the above species towards Pectobacterium carotovorum the causal agent of potato rot disease invitro indicated that they could inhibit growth of pathogen and siginificant differences among the appllied strains were observed. Based on the results of invitro xperiments six strains were selected. Bacterial suspention from these strains with OD (optical density) 0.1 in 600nm were made in distilled water. The bacterial suspention were diluted 1000 (concentration I) and 10000 (concentration II) times respectively. Potato tubers were sprayed with bacterial suspension and they were put in soil infested with P. carotovorum. Randomized block design in three replicate were used for this experiment. Tested strains showed biocontrol activity towards P. carotovorum and significant differences were observed among their efficacy were observed. They reduced the potato rot disease caused by P. carotovorum between 2.5 to 38.75 %. No significant differences were observed between the two applied concentrations of the antagonistic bacterial suspensions.