Identification of Xanthomonas axonopodis (syn:campestris) pv. pelargonii causal agent of bacterial blight on geranium (Pelargonium spp.) and research on it?s biological control

Leaf spots with yellow halo, leaf necrosis, and stem rot on were detected on ivy geranium (Pelargonium peltatum) plants in Adana and İstanbul cities. Totally 29 light yellow colonies were isolated on Nutrient agar, YDC and King?s medium B from diseased plants. In pathogenicity tests, bacteria were inoculated by sterile tootpith on stems of zonal geranium (Pelargonium x hortorum) cuttings and characteristic disease symptoms were observed within 8-10 days on inoculated cuttings. Bacteria were identified as Xanthomonas axonopodis pv. pelargonii by traditional bacteriological tests, ImmunoStrip, DAS-ELISA, PCR and whole cell fatty acid methyl ester analysis (FAME). In biological control studies, 16 soil samples were taken from geranium rhizosphere in Adana for isolating candidate plant growth promoting rhizobacteria (PGPR). Totally 234 candidate PGPR were isolated from samples. Among 60 PGPR strains were solubulized phosphorus on solid NBRIP medium. Five PGPR strains were selected for pot studies to reduce disease. Two PGPR strains reduced disease incidence at % 88-100 for leaf infections and one PGPR strain significantly reduced disease incidence at % 63 for stem infections. Key words: Pelargonium, bacteria, Xanthomonas, identification, PGPR