Outbreak of bacterial speck disease in a nursery in the eastern mediterranean region of Turkey

A severe leaf speck disease developed on container-grown tomato (Lycopersicon esculentum cv. 'Soray') plants in a commercial nursery in the Eastern Mediterranean Region of Turkey, in December 2002. Incidence of the disease was approximately 25% in the nursery. Symptoms first appeared as water-soaked (1-3 mm in diameter) and irregular-shaped lesions on cotyledons and young true leave. There was halo on young true leaves, but not on cotyledons. Lesions on true leaves later enlarged and became brown to dark brown and angular. On older leaves and petioles, lesions coalesced, causing large areas of necrosis. A fluorescent, gram negative and rod-shaped bacterium was consistently isolated from diseased tissues onto King's Medium B. All of the strains were identified as Pseudomonas syringae pv. tomato with similarity incidence of 61 to 90% based on fatty acid methyl ester (FAME) analysis in Sherlock Microbial Identification System (Microbial ID, Newark, DE, USA). All of the bacterial strains were negative for oxidase, arginine dihydrolase and pectolytic activity, but positive for levan production. They induced hypersensitive reaction on tobacco leaves. All strains were capable of acid production from glycose, glycerin, sorbitole, sucrose, mannose, fructose, L (+) arabinose, D (-) mannitol, D (+) xylose, but not from lactose, maltose, raffinose, melibiose, trehalose and D (-) arabinose. Pathogenicity was confirmed by spray inoculating three plants with 106cfu/mL adequeous suspension of bacteria from 48-h King's Medium B cultures. Inoculated plants and water-sprayed controls were covered with polyethylene bags for 24 hours in a climate room at 25°C, 70% relative humidity and 16-hour per day light period. Bags were removed and plants maintained in the climate room to observe symptoms. Typical speck lesions on the inoculated plants similar to those observed in the nursery were developed within 5-7 days after inoculation. No symptoms developed on negative control plants. The bacterium was re-isolated from the inoculated plants and characterized as identical to the original strain (GSPB 483, obtained from Gottingen, Germany). Occurrence of bacterial speck disease on greenhouse- and field-grown tomato in Turkey has been reported previously, but this is the first observation of Pseudomonas syringae pv. tomato causing disease on tomato in a commercial nursery in the Eastern Mediterranean Region of Turkey