Characterization of the antagonistic activity of a new indigenous strain of pseudomonas fluorescens isolated from onion rhizosphere

H. Afsharmanesh, M. Ahmadzadeh, M. Javan-Nikkhah, K. Behboudi
doi: 10.4454/jpp.v92i1.29
Bean damping-off caused by Rhizoctonia solani is one of the most widespread diseases of this plant. Fluorescent pseudomonads able to produce secondary antifungal metabolites can inhibit soil-borne plant pathogens. For this reason the antagonistic activity of Pseudomonas fluorescens UTPF5 against R. solani AG-4 was assessed in bean under in vivo and in vitro conditions. Production of some secondary metabolites and their impact on mycelial growth of R. solani was also studied. The results showed that UTPF5 could inhibit the growth of R. solani both in vitro and in vivo, and suppress the disease by 33.34% and 14.29% by soil drenching and seed treatment, respectively. Population density of UTPF5 decreased from about 109 CFU seed-1 to 2.07×104 CFU g-1 root after one month of growth of plants in non-infected soil. Production of HCN, siderophore and protease, and involvement of siderophore, volatile and nonvolatile metabolites on growth of the fungus were observed in UTPF5. Occurrence of the phlD gene in UTPF5 was demonstrated using PCR with the primers phl2a and phl2b. The characteristics mentioned above show that P. fluorescens strain UTPF5 is a potential biocontrol agent of R. solani.