Poster Session: New and Emerging Diseases-Bacteria

381-P

Characterization of saprophytic bacteria that react with Clavibacter michiganensis subsp. michiganensis in seed health testing.
P. SUDARSHANA (1), M. May (1), C. Kurowski (1), S. Thomas (1)
(1) Monsanto Vegetable Seeds, Woodland, CA, U.S.A.

Diagnosis of tomato canker involves examination of symptomatic plant tissue, testing with immunostrips, isolation of bacteria on selective media plates and PCR analysis. Saprophytic bacteria with similar colony morphology to Clavibacter michiganensis subsp. michiganensis (Cmm) often result in false positive reactions with Cmm immunostrips and complicate the diagnostic process. In this study, eighty five tomato tissue samples asymptomatic to Cmm and positive by immunostrip testing were analyzed. Cmm-like bacterial colonies were isolated and characterized by conventional and realtime PCR and pathogenicity testing. All tested isolates were negative by pathogenicity assays and by the industry validated realtime PCR. However, some isolates resulted in false positive reactions using the published Cmm primers, CMM5/6. Sequence analysis of bacterial 16S rDNA fragments showed similarities to Microbacterium paraoxydans and Ochrobactrum sp. Developing specific and sensitive PCR primers by comparing the genome sequences of Cmm and saprophytic isolates will be discussed.
Keywords: Bacteria-Phytoplasma-Spiroplasma-Fastidious Prokaryote, Vegetables, Tomato