غلام خداکرمیان

he possibility of biological control of the Fusarium pseudograminearum, the causal agent of wheat crown rot and seedling blight by bacterial antagonistic strains were evaluated. Healthy spike of wheat and soil samples were collected from Mazandaran and Golestan provinces. A totalof 312 bacterial strains (G+ve & G-ve) were isolated and then the inhibition zones of bacterial strains on mycellium growth of the pathogen were determined. According to the phenotypic features and electrophoretic protein patterns, representatives of bacterial strains were identified as a Pseudomonas fluorescens biov. I,Bacillus subtilisstrains 53 & 71 and Streptomyces sp.In vitro conditions, the effect of bacterial exudates, volatiles substance and thiophanat-methyl on the prevention of mycelial growth and its effects were studied on morphology of disease agent. The results showed that the exudate of strain 32 of P.fluorescens biov I. was more effective with 2.54 cm inhibition zone than the other strains. All strains were able to produce volatile substances, but the strain 53 of B. subtiliswas better than other treatments and reduced the mycelial growth of the F. pseudograminearumabout 47.77% Bacterial exudates and volatile substances of antagonist strains caused deformation and swelling of F. pseudograminearummycelia. The comparison between the 50 ppm concentrate of thiophanat- methyl and bacterial exudates showed that antagonists had a better effect on preventing growth of the disease agent, so that B. subtilisstrain 71, P. fluorescensbiovI strain32 and thiophanat-methyl reduced the mycelial growth of F. pseudograminearum 85.74%, 97.12% & 97.1% respectively. The results of greenhouse studies showed that the effect of antagonists were significant and seed and soil treatments by strain 71 of B. subtilisand Streptomycessp. strain 3 in the presence of the disease agentleads to increase plant height, dry and fresh weight of shoot and root.