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Disease Note.

First Report of Pseudomonas viridiflava Leaf Spot of Red-leaved Chicory. P. Caruso, Istituto di Patologia Vegetale, Universita degli Studi di Catania, 95123 Catania, Italy . V. Catara, Istituto di Patologia Vegetale, Universita degli Studi di Catania, 95123 Catania, Italy. Plant Dis. 80:710. Accepted for publication 15 April 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0710D.

An outbreak of a foliar disease of red-leaved chicory (Cichorium intybus L. var. foliosum cv. Rosso di Treviso) was observed in a commercial nursery greenhouse in Sicily (southern Italy) during January 1994. About 20,000 affected plantlets were unmarketable. Symptoms on one month old plantlets were predominately leaf spots, but lesions on leaf margins of older leaves occurred occasionally. Initially lesions were water-soaked; later they became brown, dry, and papery. The leaf spots were surrounded by a distinct brown border. In beds containing 300 trays (82 plants/tray) the affected plants averaged 20% with an incidence per tray up to 35%. A fluorescent bacterium was consistently isolated from diseased tissues onto King's B medium. Thirteen representative strains were tested negative for oxidase, arginine dihydrolase, and levan. They were catalase positive, hydrolyzed gelatin, and esculin. None of the strains reduced nitrate nor produced lecitinase, Tween 80 esterase, or acid from sucrose. The strains induced a hypersensitive reaction in tobacco, and they rotted potato slices. Pathogenicity of all strains was confirmed by spray inoculating four 1-month-old red-leaved chicory plants with\suspensions containing 108 CFU/ml of each of the strains. Inoculated plants and water sprayed controls were maintained in a greenhouse at 15 to 250C. The plants were covered with polyethylene bags for 24 h before and 48 h after inoculation. Small water-soaked spots surrounded by pale brown haloes developed in 3 days. By 5 to 6 days, the spots became delineated by brown borders, were necrotic and papery, and resembled symptoms on commercial plantlets. Water-sprayed controls remained symptomless. Leaf margin lesions were only occasionally observed. All the strains were characteristic of Pseudomonas viridiflava. This is the first report of leaf spot caused by P. viridiflava on chicory. However, leaf margin lesions and brown rot of head have been reported on "witloof" chicory (C. intybus L. var. sativus) (1).

Reference: (1)R. Vantomme et al. J. Phytopathol. 124:137, 1989.