In this study, the occurrence of fluorescent pseudomonads in wheat rhizosphere and the ability of 40 isolates of Pseudomonas fluorescens to suppress the G.g. tritici were investigated. Wheat plants with rhizospheric soil were collected from different fields in Tehran province, Ghazvin plain and Garmsar. Enumeration of these bacteria were carried out through spread plate method, using selective S1 medium. A pure culture of each isolate was prepared after several subculturings on the same medium. Bacterial isolates were identified on the basis of morphological, physiological and biochemical tests. The suppressive effect of strains against take-all casual agent were investigated on the NA and PDA media. Based on the results, a high population of fluorescent pseudomonads existed in wheat rhizosphere, ranging from 5×103 to 1.26×106 cfu g-1 soil, in different fields. Most strains were able to limit the growth of G.g.tritici on both NA and PDA media under in vitro conditions.However, the degree of inhibition was not the same, being observed to be varied from 0 to more than 70% for different strains.
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