Bacterial Canker Caused by Clavibacter michiganensis subsp. michiganensis on Greenhouse-Grown Tomato in the Western Mediterranean Region of Turkey

Abstract

During the 2003 winter growing season, a disease occurred on tomato (Lycopersicon esculentum L.) cvs. Selin, Astona, 198 RN, Malike, and Tulin that were growing in almost all greenhouses of Serik, Aksu, Kumluca, Demre, and Kinik in the Antalya Province, and Keçiborlu, Çandir, and Şeyhler in the Isparta Province in the western Mediterranean Region of Turkey. Disease incidence ranged from 26 to 65%, resulting in economically heavy losses. Symptoms were water-soaked, dark brown-to-black lesions on the leaf margins and asymmetrical wilting of the leaflets. In advanced stages of disease, vascular tissue had a light brown discoloration. A gram-positive bacterium was consistently isolated and formed light gray colonies with internal light gray flecks approximately 2 to 3 mm in diameter on the modified semiselective medium (SCM) (2). Thirty isolates were identified as Clavibacter michiganensis subsp. michiganensis using polymerase chain reaction (PCR) with primers CMM 5 and CMM 6 on the basis of consistent amplification of a 614-bp DNA fragment (1). The isolates were also identified as C. michiganensis subsp. michiganensis (similarity 0.810 to 0.888%) using fatty acid methyl ester (FAME) analysis and Sherlock Microbial Identification System software (Microbial ID, Newark, DE). A pathogenicity test was done by spraying a 6-week-old tomato seedling (cv. Selin) with the bacterial concentration of 108 CFU/ml in sterile water. Control tomato seedlings were only sprayed with sterile water. The inoculated plants were covered with polyethylene bags for 48 h and kept in a growth chamber at 25°C. Symptoms developed on the inoculated plants within approximately 10 days and were similar to those observed in the greenhouse. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants, and its identity was confirmed by colony type on SCM, PCR, and FAME analysis. Although it has been known to be present previously in Aegean, eastern Mediterranean, and the eastern Anatolia regions of Turkey, to our knowledge, this is the first report of bacterial canker on greenhouse tomatoes in the western Mediterranean Region of Turkey. Occurrence of the disease in almost all greenhouses may be the result of the high relative humidity present and the lack of protective bactericide applications in many greenhouses of the region. References: (1) J. Dreier et al. Phytopathology 85:462, 1995. (2) M. Fatmi and N. W. Schaad. Phytopathology 78:121, 1988.