Biological control of Bipolaris spicifera, the causal agent of wheat root rot by Pseudomonas fluorescens isolates

ABSTRACT: Bipolaris spicifera is a fungal pathogen causing damage to the wheat root and Pseudomonas fluorescens is one of the major fungal biocontrol agents found in the soil and the rhizosphere of various crop systems. The present study was carried out to evaluation the potential role of indigenous root-inhabiting Pseudomonas isolates in biological control of B. spicifera. Soil and root samples were collected from wheat fields of Gorgan province to isolate Pseudomonas fluorescens with potential antagonistic activities. 305 isolates of P.fluorescens were isolated from rhizosphere soil samples and five isolates were screened with better antagonistic effects against the fungus in petri dish experiments. Antagonistic properties of P. fluorescens isolates including K16, K14, S5, G7 and P3 were surveyed under laboratory, greenhouse and field conditions. The results showed that the isolate K14 decreased the growth of fungal mycelia in mutual inhibition tests and production of volatile compounds by 79.6 % and 81.7 %, respectively. The isolate S5 had the best ability for antibiotic production and reduced the mycelial growth up to 90 %. In greenhouse experiments, the isolate K16 was more efficient than other isolates in controlling the disease. Analysis of other growth factors also confirmed that K16 and K14 were more efficient than other tested isolates in greenhouse. In field experiments, treatment of seeds with isolates S5, K14 and K16 were as effective in controlling the disease as benomyl application.