August 25, 2004
From: ProMED-mail<promed@promedmail.org>
Source: American Phytopathological Society, Plant Disease Notes [edited] <http://www.apsnet.org/>

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis on greenhouse-grown tomato in the western Mediterranean region of Turkey
E. Basim, University of Akdeniz, Korkuteli Vocational School, Department of Plant Production, 07800, Antalya, Turkey; H. Basim, University of Akdeniz, Faculty of Agriculture, Department of Plant Protection, 07058, Antalya,
Turkey; and E. R. Dickstein and J. B. Jones, University of Florida, Department of Plant Pathology, Gainesville, 32611. Plant Dis. 88:1048, 2004; published on-line as D-2004-0624-04N, 2004. Accepted for publication 15 Jun 2004.

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 Keciborlu, Candir, and Seyhler in the Isparta Province in the western Mediterranean Region of Turkey. Disease incidence ranged from 26 to 65 percent, 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).

30 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 percent) 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 100 million 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 25C. 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 1st 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.

[This is the 2nd outbreak of bacterial canker in tomato reported in the region, the lst being in 2001. _Clavibacter michiganensis_ subsp. _michiganensis_ (Cmm) affects field and greenhouse production systems, often inducing severe, in some cases total, crop loss. Tomato and pepper are major hosts. The primary source of the pathogen is contaminated seeds and transplants. The pathogen can survive in non-decomposed tomato crop residues and on seed for up to 5 years. Infested seed is the principal means of long-distance spread. Solanaceous weeds can be alternate hosts of the pathogen. Disease management involves the use of disease-free seed, planting resistant cultivars, and enforcement of vigilant phytosanitary procedures (decontamination of supporting stakes and equipment in greenhouse production systems and rotation of the crop in field conditions). Some degree of control can be obtained by applying chemical and antibiotic treatments, but they should be used sparingly so as to prevent development of resistant strains of the pathogen. According to the manufacturer, Virkon S is effective in disinfecting tomato seeds from canker infection without any adverse effects on seed germination or seedling stand.

ProMED-mail has no financial relationship with Antec International, the manufacturer of Virkon S. - Mod.DH]