First report of Pseudomonas mediterranea causing tomato pith necrosis in Argentina

During the summers of 2007 and 2008 fruiting tomato plants (Solanum lycopersicum cv. Orco) from commercial glasshouses near La Plata, Argentina (35S 57W) showed abundant adventitious root production, apical chlorosis of leaves and a brown discoloration of the stem pith. These symptoms were similar to those reported by López et al. (1994) and Catara et al. (2002) on tomatoes affected by Pseudomonas corrugata or P. mediterranea. Bacteria consistently isolated from stem lesions formed cream-coloured, glistening, convex colonies on sucrose peptone agar and were non-fluorescent on King’s medium B. Four strains were selected for further study. All were aerobic, Gram-negative rods with PHB inclusions. In LOPAT tests, all induced a hypersensitive response in tobacco plants, were oxidase positive, did not cause soft rot of potato tubers, and were negative for levan and arginine dihydrolase. Colonies developed at 28C and 37C but not at 41C. Additional characterization was achieved by API 20 NE tests strips (Biomerieux®). Reference strains 536·7 (Spain), 592·4 (Spain) and CFBP 10906 (France) of P. mediterranea and strain NCPPB 2445 of P. corrugata were included in all tests for comparison.Facultad de Ciencias Agrarias y ForestalesCentro de Investigaciones de Fitopatologí