First report of Pith Necrosis of tomato caused by Pseudomonas mediterranea in Turkey

During winter and spring of 2001-2003, 83 greenhouse-grown tomato (Lycopersicon esculentum) crops in Antalya and Mugla, in the Mediterranean and Aegean regions of Turkey, were surveyed for pith necrosis. Bacteria were consistently isolated on nutrient agar (NA) or King's Medium B (KB) from the stems of tomato plants of the most commonly-grown cultivars (cvs. Selin and Astona) showing brown water-soaked and dry pith necrosis symptoms. Bacterial suspensions (50 µl, 108 cfu per ml) in sterile distilled water, prepared from 24 h cultures, were injected into the axils of the first true leaves of four-week-old tomato plants (cvs. Selin and Astona, six plants of each cultivar per strain). A reference strain of Pseudomonas mediterranea CFBP5404 (from France) and sterile distilled water were used as positive and negative controls respectively. After inoculation, plants were enclosed in polyethylene bags for 3 days to maintain high humidity. Symptoms did not develop on negative control plants but were observed after 14 days on plants inoculated with bacteria (Fig. 1).

The pathogenic bacteria were aerobic, produced smooth colonies on NA, were non-fluorescent on KB, oxidase positive, did not produce levan, were non-pectolytic and reduced nitrates to nitrites (Lelliot & Stead, 1987) as described for both P. corrugata and P. mediterranea. In PCR using both type I primers (PC5/1 and PC5/2) and type II primers (PC1/1 and PC1/2) (Catara et al., 2002), 71 of the 83 bacteria isolated were identified as P. corrugata by amplification of a 1100 bp DNA fragment, but 12 were identified as P. mediterranea by amplification of a 600 bp DNA fragment (Fig. 2) identical to that of the reference strain of P. mediterranea CFBP5404.

Identification as P. mediterranea was also confirmed by comparing BOX-PCR profiles of the isolates to those of the reference cultures of P. corrugata and P. mediterranea (Fig. 3). Pith necrosis of tomatoes caused by P. corrugata and P. fluorescens has been reported previously in Turkey (Demir, 1990; Saygili et al., 2004). This is the first report of P. mediterranea causing tomato pith necrosis in Turkey.