Biological control of Rhizoctonia solani by Pseudomonas strains isolated from the rhizosphere
Subject Areas : Plant MicrobiologyMitra Omidinasab 1 , Mostafa Darvishnia 2
1 - M.Sc. student, Department of Plant Protection, College of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
2 - Associate Professor, Department of Plant Protection, College of Agriculture, Lorestan University, Lorestan, Iran.
Keywords: Damping off, Seed rot, Antagonistic strains, Rhizosphere bacteria,
Abstract :
Background & Objectives: Bean (Phaseolus vulgaris L.) is now widely used as a major food product in many tropical areas and semi-temperate and temperate areas of America, Europe, Africa as well as Asia. Damping off and seed rot are the most frequent and damaging diseases of the legumes worldwide which are caused by Rhizoctonia solani. The purpose of this study was isolation and characterization of rhizosphere bacteria for the biocontrol of the R. solani in the bean. Material & Methods: Four isolated bacteria from bean plants rhizosphere soil in Lorestan province farms were evaluated in vitro as a potential antagonist of the fungal pathogen. In vitro inhibition of R. solani mycelium growth by rhizosphere bacteria were tested on rye agar media. The degree of inhibition in each medium was determined by measuring the halo around the bacterial strains. Results: Sequencing of 16S rRNA and its comparison with Gen Bank sequence database revealed that antagonistic strains belong to Pseudomonas fluorescens, Pseudomonas aeruginosa, Pseudomonas monteilii, and Pseudomonas putida species. All the strains significantly inhibited R. solani growth, resulting in more than 40% inhibition on potato dextrose agar medium (PDA). The results showed the most inhibition by P. putida, and the lowest by P. aeruginosa. Conclusion: Rhizoctonia root-rot is a highly destructive disease in most areas of the world. Biological control using natural microorganisms offers a powerful alternative to chemical control of Rhizoctonia root-rot diseases.
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