Phytophthora infestans is a pathogen threatening potato and tomato tillages. Environmentally safe biological methods are searched for the prevention against this pathogen. Many biocontrolling agents occur in plants or on their surfaces. Our studies were aimed at searching for effective antagonists against P. infestans among the isolates of endophyte and epiphyte bacteria. 37 endophyte and 26 epiphyte bacterial strains isolated from Equisetum arvense, Elymus repens and Chenopodium album L. were studied. The bacterial strains were screened for their antagonistic activity against Phytophthora infestans. The inhibitory effect of the bacteria was estimated based on the calculation of the per cent of relative growth. All tested isolates showed antagonistic properties against P. infestans. The strongest activity was observed for the B. subtilis strain. Plant species and the tested parts of the plants had an important influence on the antagonistic activity of bacterial strains isolated from these plants. The endophyte growth rate inhibition of P. infestans was higher than for the epiphyte strains and was over 40% for most isolates. Bacterial biocontrolling agents should be searched among endophytes of the studied plants and not among bacteria colonizing their phyllosphere.

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