Characterization of Pseudomonas fluorescens strain CV6 isolated from cucumber rhizosphere in Varamin as a potential biocontrol agent

• Published in: Australian Journal of Crop Science Vol. 4; no. 9; pp. 676 - 683
• Main Authors: Maleki, M, Mostafaee, S, Mokhtarnejad, L, Farzaneh, M
• Format: Journal Article
• Language: English
• Published: Lismore, N.S.W Southern Cross Publishers 2010
• Subjects: biological control agents; cucumbers; Cucumis sativus; Experiments; Growth; Growth (Plants); isolation; Phytophthora drechsleri; Plant growth-promoting rhizobacteria; plant pathogenic fungi; Pseudomonas fluorescens; Pseudomonas fluorescens strain CV6; Rhizobiales; rhizosphere; Seeds; strains; Iran
• ISSN: 1835-2707; 1835-2693; 1835-2707

Antagonistic rhizobacteria, more specifically fluorescent pseudomonads and certain species of Bacillus, are known to control of fungal root diseases of agronomic crops. In this study, 144 bacteria were isolated from cucumber rhizosphere and screened as potential biological control agents against Phytophthora drechsleri, causal agent of cucumber root rot, in vitro and greenhouse condition. On the basis of dual culture assays, eight isolates were selected for root colonization, PGPR and greenhouse studies. Among these isolates, isolate CV6 exhibited the highest colonization on the roots and significantly promoted plant growth under in vitro condition. In greenhouse studies mortality in pots treated with strain CV6 was very low and percent of healthy plants were 85.71%. Based on biochemical and physiologic tests and 16SrDNA homology, this isolate identified as Pseudomonas fluorescensstrain CV6. Strain CV6 was shown to have broad spectrum in vitro antibiotic activity against 11 additional plant pathogens. It was able to produce considerable amount of siderophore and acid indole-3-acetic acid (IAA). With the addition of tryptophan from 50 to 500 mg/ml the production of IAA was increased up to 15.3 micro g/ml. The bacterium showed positive reactions for HCN, catalase, protease, and phosphatase, and negative for the production of pectinase, lipase and cellulase. Results from this study provide comprehensive information on nutritional requirements and biocontrol mechanisms of strain CV6 that can be used for commercial use and appropriate application of this bacterium.