Characterization of Xanthomonas hortorum pv. pelargonii Isolated from Geranium in Serbia

Geranium leaves and stems with symptoms of bacterial blight were collected from commercial greenhouses during the last decade in Serbia. In total, 17 isolates with colony morphology typical for the genus Xanthomonas were characterized with pathogenicity, biochemical, serological, and molecular assays. All 17 isolates reacted positive in a polymerase chain reaction (PCR) using XcpM1 and XcpM2 primers specific for Xanthomonas hortorum pv. pelargonii. In pathogenicity tests on Pelargonium zonale (leaf and stem inoculation), all isolates caused typical symptoms on leaves starting 2 days after inoculation as sunken, water-soaked, irregular lesions, and 6 to 8 days after inoculation on stems as necrotic lesions also showing yellow exudate. Symptoms resulted in general wilting of inoculated plants 20 days after inoculation. Selected phenotypic tests indicated that all isolates showed the same results as described for the bacterium X. hortorum pv. pelargonii. Repetitive sequence-based PCR typing using BOX and ERIC revealed that all isolates showed two fingerprinting profiles but (GTG)5 and REP did not reveal differences. Multilocus sequence typing of partial sequences of rpoD, dnaK, fyuA, and gyrB genes of tested isolates and sequences obtained from GenBank of Xanthomonas pathovar pathotype strains did not reveal genetic variability among the isolates, showing the same gene sequence pattern.