Identification and pathogenicity of the bacterium associated with blight of gerbera in Federal District

Resumo

The gerbera is among the most extensively exploited flowers in Brazil, prominent in the country’s national agribusiness. In 2013, leaf samples of gerbera plants showing symptoms of bacterial blight were collected in six cut-flower high tunnels, located in the settlement of Núcleo Rural Alexandre Gusmão, Brazlândia-DF, and these presented 80% of infected plants mainly on lower leaves. From leaf segments, rod-shaped Gram-negative bacteria were isolated, producing white colonies and fluorescent pigment in King-B medium. The bacterial isolates obtained were subjected to phenotypic and molecular characterization, including pathogenicity tests, LOPAT and partial sequencing of the 16S rDNA gene. The seven isolates obtained were Gram-negative, aerobic, oxidase-positive, produced fluorescent pigment, induced hypersensitivity in tobacco leaves, used sorbitol and glutamate, were pathogenic to 24 different plant species and the sequences of rDNA showed 99 % identity with P. cichorii. By corroboratively analyzing the above-mentioned tests it was concluded that the isolates belong to the Pseudomonas cichorii species. To our knowledge, this is the first report of P. cichorii in gerbera in the Federal District