August 23, 2004
From: ProMED-mail<promed@promedmail.org>
Source:  American Phytopathological Society, Plant Disease Notes [edited]

An outbreak of bacterial speck caused by Pseudomonas syringae pv. tomato on tomato transplants grown in commercial seedling companies located in the western Mediterranean region of Turkey

H. Basim, University of Akdeniz, Faculty of Agriculture, Department of Plant Protection, 07058, Antalya, Turkey; E. Basim, University of Akdeniz, Korkuteli Vocational School, Department of Plant Production, 07800, Antalya, Turkey; S. Yilmaz, 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. 88:1050, 2004; published on-line as D-2004-0624-05N, 2004. Accepted for publication 15 Jun 2004.

A serious outbreak of a leaf spot disease was observed on tomato transplants grown in commercial seedling companies in southwestern Turkey (Antalya) during the springs of 2002 and 2003. Disease incidence was more
severe in the western Mediterranean Region of Turkey. Occurrence of the outbreak resulted in approximately 20 and 25 percent seedling losses in the springs of 2002 and 2003, respectively.

The initial symptoms consisted of pronounced water-soaked, dark brown-to-black spots on young expanding leaves that were 1 to 2 mm in diameter. Later, a number of leaf spots on older leaves enlarged and coalesced, causing leaf desiccation and finally, seedling death. In addition, in 2003 the disease incidence was approximately 5 percent in 142 commercial greenhouses. Tomato production was unaffected since significant outbreaks did not occur on greenhouse plants. No fruit symptoms were observed.

26 strains were isolated from diseased tomato seedlings and plants from different greenhouses located in different places and all were gram-negative and fluorescent on King's B medium. All strains were levan and gelatin liquefaction-positive and oxidase and arginine dihydrolase-negative. None of the 26 strains utilized erythritol and L-lactate as the sole carbon source (1,2). Fatty acid analysis identified the strains as _Pseudomonas syringae_ pv. _tomato_ with similarity indices ranging from 0.876 to 0.932 percent.

Pathogenicity of the isolates was confirmed on 4-week-old tomato seedlings (cv. Biotek Selin) sprayed with the bacterial suspensions containing 100 million CFU/ml of sterile water. Later, a number of leaf spots on the leaves enlarged and coalesced, causing leaf desiccation. Inoculated and control tomato seedlings were covered with polyethylene bags and placed in a growth chamber at 25 deg C for 48 h and then the bags were removed.

Small (1 to 2 mm), water-soaked, dark brown-to-black spots similar to those observed in the greenhouses of commercial seedling companies and commercial greenhouses that produce tomato developed on the young expanding leaves of inoculated plants within 7 to 10 days. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants and identified as a strain of _Pseudomonas syringae_ pv. _tomato_. Koch's postulates were fulfilled.

To our knowledge, this is the first report for the occurrence and outbreak of the bacterial speck disease on tomato transplants in greenhouses of commercial tomato seedling production companies in Turkey.

References:
(1) D. C. Hildebrand et al. Pages 60-80 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. N. D. Schaad, ed. The American Phytopathological Society, 1988.
(2) J. B. Jones et al. Plant Dis. 70:151, 1986.

[This is the 2nd outbreak of bacterial speck disease caused by _Pseudomonas syringae_ pv. _tomato_ (Pst) in Turkish glasshouses. There are 2 possible routes for infection. The lst is that tomato seed contaminated with Pst was used to establish seedling transplants. The 2nd is that the seedling production facilities were contaminated by the Pst. In either case, the bacterium can be efficiently spread. Disease management includes use of seed produced on disease-free plants, disease-free transplants, crop rotation with non-solanaceous crops for at least 2-3 years between tomato crops, and resistant cultivars. Proper sanitation such as disinfecting interior glasshouse surfaces is strongly recommended before seeding or transplanting.

Reference was made to AMITOM, which is an association grouping professional organisations of tomato processors in the Mediterranean region based in Avignon, France. I have included a useful informative link that describes tomato production in Turkey.

<http://www.tomate.org/pdf/TURKEY2002_EN.pdf> - Mod.DH]