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Disease Note.

First Report of Bacterial Spot of Celery Caused by Pseudomonas cichorii in Argentina. A. M. Alippi, Laboratorio de Fitopatologia, Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, calles 60 y 119, c.c. 31, 1900 La Plata, Argentina and Comision de Investigaciones Cientificas. Plant Dis. 80:599. Accepted for publication 29 February 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0599C.

In 1995, small, angular, water-soaked spots were observed on celery leaves (Apium graveolens L. cv. Golden Boy ) in a commercial field in La Plata, Argentina. When the spots occurred in large numbers, the whole leaf became chlorotic. Older lesions were dry and rusty brown with angular edges. Some plants showed elongated, dark brown lesions about 2 to 5 mm long on petioles.A bacterium consistently isolated from leaf and petiole spots produced a diffusible green-fluorescent pigment when cultured on King's medium B. The bacterium was a Gram-negative rod averaging 0.4 x 2.14 µm, non-spore-forming and catalase positive. In LOPAT (levan-oxidase-potato rot-arginine dihydrolase-tobacco hypersensitivity) tests, all strains induced a strong hypersensitive reaction in tobacco leaves and were oxidase positive, and negative for soft rot of potato, levan production, and arginine dihydrolase, indicative of group III of fluorescent pseudomonads. All strains showed oxidative metabolism of glucose and were able to use asparagine as the sole carbon source. Acid was produced aerobically from D-mannitol but nol from D-(-)arabinose, sorbitol, or inositol. The strains were positive for utilization of L(+)tartrate but did not utilize Tween 80 or reduce nitrates to nitrites. No growth occurred at 37C. All strains were sensitive to 10 µg of streptomycin in an antibiotic disk assay and to copper sulfate at concentrations of 0.16 and 0,64 mM in an agar plate assay (1). Symptoms similar to the lesions observed in the commercial field were observed on celery leaf blades 7 days after inoculation by misting with a bacterial suspension of 107 cells/ml. Additional pathogenicity tests were performed on tomato (Lycopersicon esculentum Mill, hybrid LSL TT-6), cabbage (Brassica oleracea L. var. capitata cv. Ruby perfection), broccoli (Brassica oleracea. L. var. botrytis cv. Atlantic); cauliflower (B. oleracea var. botrytis cv. Snow March); chrysanthemum (Chrysanthemum x morifolium Ramat), and common chicory (Cichorium intybus L.). The bacterium was reisolated from lesions of inoculated plants. The pathogen was identified as Pseudomonas cichorii (2) based on morphological, biochemical, and physiological characteristics and host range. This is the first report of Pseudomonas cichorii in Argentina.

References: (1) K. Pohronezny et al. Plant Dis 78:150. 1994. (2) J P. Wilkie and D W. Dye. N.Z J. Agric. Res. 17:123. 1974.