Identification of soil inhabiting bacteria of vineyards in Zanjan province and investigation of their antagonistic effect on Rhizobium vitis the causal agent of root and crown gall

Crown and root gall caused by Rhizobium vitis, is one of the most important diseases of grapevine worldwide. In Iran٫ the disease has been reported in different areas such as Zanjan province. Despite the importance of the disease in the orchards٫ there is no an effective control measure for the disease. In this study the most important soil-inhabiting bacteria from vineyards in Zanjan province were isolated and were identified. Antagonistic effects of some isolates were investigated against the pathogen. For this mean٫ samples were collected from grapevine roots with surrounding soil in vineyards in different areas of the province. Based on morphological٫ physiological and biochemical characteristics٫ 200 isolates were selected and their inhibitory effects were investigated on the pathogen in vitro for antibiotic production. Fifty isolates with the most inhibitory-effect in the tests were identified to genus and species levels. Some isolates identified as Pseudomonas spp. were further studied for the hcnABC gene. Biochemical tests identified representatives as Pseudomonas fluorescens biovare I٫ III and V٫ P. putida٫ Basillus subtilis٫ Pseudomonas sp. ٫ and Bacillus sp. Identified Pseudomonads showed significant inhibitory effect on R. vitis on King-B medium also via HCN production. In the PCR٫ hcnABC gene was amplified from five Pseudomonas strains. Indeed, seven strains with the most inhibitory-effect in vitro were selected across identified Pseudomonas and Bacillus strains and their antagonistic effect on the pathogen population was studied in the soil environment. Based on the results, all tested bacteria showed significant inhibitory effect on the pathogen population. However٫ Pseudomonas fluorescens bv. V, III and Bacillus subtilis were more effective.