FIRST REPORT OF PECTOBACTERIUM CAROTOVORUM subsp. CAROTOVORUM CAUSING STEM ROT ON GREENHOUSE TOMATOES IN SYRIA

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During winter 2010 and 2011, stem rot symptoms were seen on greenhouse-grown tomato (Lycopersicom esculentum) plants in Tartous governorate (Syria). Affected plants showed darkening and water soaking of the stem and vascular browning, followed by wilting and death. These symptoms were similar to those re- ported from Tunisia by Hibar et al. (2007). Bacteria isolated on King’s medium B (KB) from rotting stems, formed round, slightly convex, white- to cream-coloured colonies. Twelve isolates were Gram-negative, not fluorescent on KB, facultative anaerobic in Hugh and Leifson medium, negative for levan production, oxi- dase, arginine dihydrolase, acid from malonate and utilization of keto-methyl glucoside and catalase-positive and induced hyper- sensitive reaction on tobacco and soft rot of potato slices. Acid was produced from trehalose, sucrose, arabinose, rafinose, but not form arabitol, sorbitol and maltose. These tests indicated the presence of P. carotovorum subsp. carotovorum (Pcc), whose iden- tity was confirmed by PCR, using the Pcc-specific primer pair Y1: 5’-TTACCGGACGCCGAGCTGTGGCGT-3’ and Y2: 5’- CAGGAAGATGTCGTT ATCGCGAGT-3’ (Helias et al., 1998). Pathogenicity tests consisted in needle puncture inoculation of tomato seedling stems with bacteria suspension in distilled water (108 CFU/ml) whereas controls were injected with sterile distilled water. All plants were covered with polyethylene bags for 24 h and placed in a climatic chamber at 25°C, 80% RH and a 12 h phothoperiod. After three to seven days, all inoculated plants, but not controls, showed darkening and water-soaking of the stem and vascular browning. Some plants died within three days. To our knowledge this is the first record of the occurrence of soft rot, caused by Pcc on greenhouse tomatoes in Syria.