Management of Common Blight Disease Caused by Xanthomonas axonopodis pv. phaseoli by Using the Plant Growth-Promoting Rhizobacteria (PGPR) and Some Plant Extracts

Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that actively colonize plant roots and increase plant growth and yield. Promising plant extracts for the management of plant diseases are environmentally safe, long-lasting and extracts of certain plants contain alkaloids, tannins, quinones, coumarins, phenolic compounds and phytoalexins. The aim of this study was to evaluate the effectiveness of five PGPR and fifteen plants extract on bean plants against Xanthomonas axonopodis pv. phaseoli, the causal agent of common blight of bean, and their effects on plant growth in glasshouse conditions. The disc diffusion method with a minor modification was used for testing of inhibitory activity. The minimum inhibitory concentration (MIC) values were determined by using modified disc diffusion method at five different concentrations and streptomycin sulphate was used as control chemical. Rhizobacteria strains isolated from rhizospehere and phyllosphere of some healthy plants were applied with a suspension of 10⁸ cfu ml^-1 after sowing at 3, 5 and 10 days and a virulent strain of X. a. pv. phaseoli (Xap12) was inoculated by inserting a hypodermic needle. Some growth parameters (plant height, fresh and dry matter weight) were determined 30 days later after applications and the disease symptoms were evaluated by 0-5 scale in the experiments. As a result of all experiments, applications of PGPR and some plant extracts suppressed the bacterial disease of bean and increased growth parameters. This study indicated that PGPRs and some plant extracts may be used in prevention programs to combat the common blight disease.

 This study was supported by Selcuk University Scientific Researches Coordinators