First report of bacterial wilt caused by Ralstonia solanacearum biovar 2 on tomato in Turkey

In the summer of 2006 severe wilt symptoms of tomato plants in some fields in the Canakkale province of the Aegean Region of Turkey were observed. Symptoms started as leaf drooping followed by wilting of whole plants within a few days, leading to total plant collapse. Vascular discolouration and browning of the pith in the lower stem occurred. On the stem of some plants, adventitious roots were formed. White, irregular and fluidal colonies with blood red colouration in the centre were consistently isolated from diseased tissues plated onto mSMSA medium (Englebrecht, 1994; Elphinstone et al., 1996).

Isolates were identified as Ralstonia solanacearum (Smith)Yabuuchi et al. by biochemical, immunofluorescense (IF) and Real-time PCR tests. They utilised maltose, lactose and D(+) cellobiose, but not mannitol, sorbitol and dulcitol in accordance with biovar 2 . In IF tests, fluorescing cells with typical morphology were observed at antibody dilutions of 200-12800. Real-time PCR was performed using biovar 2 specific primers and probe as described by Ozakman and Schaad (2003). Ct values of 18.46 and 22.27 were obtained from 2 isolates respectively. Pathogenicity of the strains was confirmed on two week old tomato plants (cv. Rio Grande) inoculated with a bacterial suspension containing 10⁶ cfu/ml using a hypodermic syringe . Control plants were inoculated with sterile water. Inoculated plants were grown in a growth chamber for 15 days at 25°C and 70-80 % humidity. Wilting symptoms were observed 5-6 days after inoculation. No symptoms developed on sterile water controls. The bacteria were re-isolated and identified as R. solanacearum biovar 2. This is the first report of R. solanacearum biovar 2 on tomato in Turkey.