New Disease Reports
New Disease Reports (2008) 18, 33.
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First report of Clavibacter michiganensis subsp. sepedonicus causing bacterial ring rot of potato in Turkey

Ş. Altundağ 1, A. Karahan 1*, A.O. Kılınç 1 and M. Özakman 2

* aynur_karahan@zmmae.gov.tr

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Accepted: 04 Dec 2008

During the 2007 seed potato monitoring programme in Turkey, 336 tuber samples from Kayseri province were tested for the presence of ring rot and brown rot diseases according to the EC Directives 93/85/EEC (Anon., 1993) and 98/57/EC (Anon., 1998). Three samples gave a positive immunofluorescence test (IF) result for the ring rot pathogen, Clavibacter michiganensis subsp. sepedonicus (Spieckermann & Kotthoff) Davis. et al.(Cms). Tuber heel end extracts were plated onto NCP-88 medium. Creamy-white, smooth, mucoid-fluidal colonies were selected and purified. External symptoms were observed on tubers of all three samples (two of cv. Soleia and one of cv. Safrane) as sunken and cracked areas (Fig. 1). When tubers were cut transversely, typical symptoms were seen through the vascular ring of tubers as a brown cheesy decay. Bacterial ooze was expressed when tubers were squeezed (Fig. 2). A positive IF result was obtained directly from the ooze. Isolates hydrolysed aesculin and produced catalase. They did not produce acid from glycerol, lactose, rhamnose and salicin. They gave negative results for oxidase activity, growth at 37°C, urease activity, starch hydrolysis, tolerance of 7 % NaCl, indole production and gelatine liquefaction.

Suspensions of pure colonies in water (c. 109 cfu per ml from each of the three samples were used for real-time PCR (Schaad et al. ,1999), with Ct values of 16.53, 16.21 and 32.2. Suspensions (106 cfu/ml) were injected into stems of ten Solanum melongena plants (cv. Black Beauty) at leaf stage 3. Control plants were inoculated with sterile water. Plants were incubated at 21°C and 70-80 % humidity. First symptoms were observed as dark green areas on leaves after ten days followed by wilting and necrosis (Figure 3). Cms was re-isolated and identified.

An intensive survey in 1988-1989 had shown that the potato growing areas of Turkey were free of the ring rot pathogen (Benlioğlu et al., 1991). This is the first report of Cms in Turkey. Strict control measures have been taken in contaminated and potentially contaminated fields since Cms is a regulated quarantine organism in Turkey.

Figure1+
Figure 1: External tuber symptoms of ring rot showing sunken and cracked areas
Figure 1: External tuber symptoms of ring rot showing sunken and cracked areas
Figure2+
Figure 2: Ring rot symptoms of vascular ring as a brown cheesy decay and bacterial ooze
Figure 2: Ring rot symptoms of vascular ring as a brown cheesy decay and bacterial ooze
Figure3+
Figure 3: Positive pathogenicity test on eggplant
Figure 3: Positive pathogenicity test on eggplant

References

  1. Anon., 1993. Council Directive 93/85/EEC on the control of potato ring rot . Official Journal of the European Communities L 259, 1-25.
  2. Anon., 1998. Council Directive 98/57/EC on the control of Ralstonia solanacearum (Smith) Yabuuchi et al. Official Journal of the European Communities L 235, 1-39.
  3. Benlioğlu K, Öktem Y.E, Özakman M, 1991. Bacterial diseases of potatoes in the major potato-growing areas in Turkey. Bulletin OEPP/EPPO Bulletin 21, 67-72.
  4. Schaad N.W, Berthier-Schaad Y, Sechler A, Knorr D, 1999. Detection of Clavibacter michiganensis subsp. sepedonicus in potato tubers by Bio-PCR and an automated real-time fluorescence detection system. Plant Disease 83, 1095-1100
This report was formally published in Plant Pathology

©2008 The Authors