43 Serious Outbreak of Clavibacter michiganensis subsp. michiganensis on Tomato in Southern Italy A. Fanigliulo, A. Viggiano and G. Piegari Bioagritest Srl. a Centro Interregionale di Diagnosi Vegetale Zona PIP lotto E2. 85010 Pignola (PZ) Italy A. Crescenzi b Dipartimento di Biologia, Difesa e Biotecnologie Agro-Forestali Università degli Studi della Basilicata Campus Macchia Romana 3A310 85100 Potenza (PZ) Italy Keywords: quarantine pathogen, Clavibacter michiganensis subs. michiganensis, bacterial cancer, tomato Abstract An outbreak of bacterial cancer was observed in tomato fields in the main tomato growing area of Apulia and Basilicata regions, respectively in the campaigns of Foggia and Matera province, in 2010 summer, starting 20-30 days from transplant. Symptoms of systemic wilt of the plant, necrosis of the leaf margin and upward curling of the leaf edges, dark streaks on stems and stem cankers, spots with raised brown centers and external marbling on fruits surrounded by an opaque white halo were observed in open field in the period following to blooming. The disease reached, in some instances, above all at the beginning of ripening, a 100% incidence, with the complete loss of the crop. Detection assays for Clavibacter michiganensis subsp. michiganensis were performed in order to ascertain the etiologic agent, in any case of symptom observation. The diagnostic procedure comprised isolation from infected tissue, presumptive diagnosis with a rapid test, identification of presumptive isolates and determination of pathogenicity. All symp- tomatic plants resulted infected with the bacterium under investigation. They be- longed always to the same cultivar of tomato, ‘Uno Rosso’, and to the same seed batch. This led us to believe that bacterial infection was associated with tomato seed. The suspected tomato seed batch ‘Uno Rosso’ was analyzed using the method for the detection of C. michiganensis subsp. michiganensis on tomato seed (International Seed Federation), working on a slight modification because the seeds under investigation were pills. The result was that the seeds were positive to C. michiganensis subsp. michiganensis. About 40 millions of these tomato pills (100 kg tomato seeds) were distributed, with imaginable consequences on plant health of the industrial tomato crops. This event allowed us to reflect on how important is the use of health seed for the preservation of our agro-systems. INTRODUCTION An outbreak of bacterial cancer was observed in tomato fields in the main tomato growing area of Apulia and Basilicata Regions, Southern Italy, respectively in the campaigns of Foggia and Matera province, in 2010 summer, starting 20-30 days from transplant. Symptoms were observed in open field in the period following to blooming. They consisted in systemic wilt of the plant, often starting unilaterally on a lower leaf; marginal necrosis of wilted leaves (brown, dead tissue) and upward curling of the leaf edges; a creamy-white, yellow or reddish-brown discoloration of vascular tissue in stems, petioles and peduncles of wilted plants; pale-green water-soaked areas between leaf veins which become necrotic, resembling sun-burn; adventitious roots on the stems; light yellow to brown streaks/cankers on stems; a thin, yellow to reddish-brown discolouration of the a info@bioagritest.it; www.bioagritest.it b aniello.crescenzi@unibas.it Proc. III rd IS on Tomato Diseases Eds.: A. Crescenzi and A. Fanigliulo Acta Hort. 914, ISHS 2011