Potato is considered as an important product all over the world for food supply. Common scab disease of this product caused by Stereptomyces scabies is a serious disease which diminishes product quantity and marketability. We studied an environmental friendly method to control the disease and for this purpose interaction between the causal agent of the disease and rhizospheric bacteria were investigated. Pathogenic S. scabies strains were isolated from infected potato tuber on potato dextrose agar (PDA) medium, and their pathogenicity was confirmed. For biocontrol of the potato scab disease, a total of 74 strains of bacteria were isolated from healthy tubers and examined for their ability to inhibit S. scabies on PDA medium. Interaction between potato rhizosphere bacteria and Stereptomyces scabies under laboratory and greenhouse conditions were studied in a complete randomized design with three replicates. Results showed that EMJ12, EMJ42, and EMJ14 strains with a mean diameter of growth inhibition zone 3.10, 3.10, and 2.36 centimeter were the most effective in laboratory respectively. Assessment of disease severity reduction by these bacterial strains in greenhouse showed that the EMJ8, EMJ14, and EMJ12 isolates reduced the disease 80%, 80%, and 40% respectively. Results of bacterial identification by standard bacteriological methods showed that the isolated strains were belonging to Pseudomonas, Bacillus, Ralstonia, Genera and Entrobacteriaceae family. Sequences of EMJ14 strains to sequence the bacterium Pseudomonas salomonii available in NCBI database sites were similar.
