First Report of Bacterial Leaf Spot Caused by Pseudomonas cichorii on Schefflera arboricola in Turkey.

Abstract

In late winter and spring of 2006 and 2008, leaf spots with yellow halos were observed on dwarf schefflera (Schefflera arboricola cvs. Gold Capella, Trinette, and Green Gold) that were grown as potted plants in two commercial ornamental greenhouses in Adana and Mersin, Turkey. Average disease incidence was assessed as 10% during the term of the study. Isolations were made from leaf spots symptoms on King's medium B. Bacteria consistently isolated from diseased tissues formed green fluorescent colonies on the medium. Ten representative bacterial strains were examined and found to be gram negative, rod shaped, and aerobic, levan, pectolytic, and arginine dihydrolase negative, and oxidase positive. They all induced a hypersensitive response in tobacco (Nicotiana tabacum cv. Samsun). All strains were identified as Pseudomonas cichorii with similarity indices of 79 to 99% based on fatty acid methyl ester (FAME) profiles determined by Sherlock Microbial Identification System software (TSBA 6 v. 6.00; Microbial ID, Newark, DE). Pathogenicity of the strains was confirmed on five dwarf schefflera plants by leaf tissue infiltration with bacterial suspensions (107 CFU ml-1) in sterile distilled water. P. cichorii NCPPB 3802 and sterile water were used as positive and negative controls, respectively. The same symptoms as those observed in the commercial greenhouses were observed on dwarf schefflera leaves within 12 to 15 days after inoculation. The bacteria were reisolated from the inoculated plants and identified as the same as the original strain by conventional tests and FAME analysis. Negative control plants remained disease free. Occurrence of bacterial leaf spot caused by P. cichorii on vegetable crops in Turkey (1,3) and dwarf schefflera in other countries (2) has been reported previously, but to our knowledge, this is the first report of the observation of P. cichorii on dwarf schefflera in Turkey.