Clavibacter michiganensis subsp. michiganensis

Taxonomy

Domain	Bacteria
Phylum	Actinomycetota
Subclass	Actinobacteridae
Order	Actinomycetales
Family	Microbacteriaceae
Genus	Clavibacter
Species	Clavibacter michiganensis

Scientific Name

Clavibacter michiganensis ssp. michiganensis

Common Name

bacterial canker and wilt of tomato

Author:John Bonkowski, Bacheline Joseph, Deanna Bayo, University of Florida

Reviewed by:Name, Organization

Pathogen

Clavibacter michiganensissubsp. michiganensis is a gram-positive, non-motile, rod-shaped, aerobic bacterium that causes bacterial canker in tomatoes. Bacterial canker can negatively impact the commercial tomato industry worldwide by killing young plants and disfiguring fruit.

Symptoms and Signs

Bacterial canker can result in a wide array of symptoms depending on environmental conditions, age of the host plant, cultivar susceptibility, and initial means of entry into the plant. Symptoms include stunting, wilting, vascular discoloration, cankers on stems, and lesions on the fruits. Systemic wilt of the plant due to blockage of xylem vessels is the primary symptom of infection. Systemic infections generally occur by entry of bacterium through wounds directly into vascular tissue or via seedborne transmission (5).

Localized infections such as marginal necrosis and leaflet spotting occur when the bacterium enters broken trichomes or natural openings on the leaves. Marginal necrosis, also referred to as the leaf firing stage, is an early symptom in which the lower margins of the leaves appear dark brown and dry. Progressive widening of the necrotic margin may lead to shriveling of leaves and entire stems.

Older leaves can appear necrotic, curled, shriveled, wilted, and/or chlorotic. Stem infections eventually develop cankers that split vertically along the stem. Squeezing an infected, cut stem may produce a yellow exudate from xylem vessels. The bacterium can colonize the tissues of the cortex and pith near the xylem vessels causing creamy, white, yellow, or reddish brown lines along the vascular system (5). Fruit may fall from the tree without developing or may not ripen evenly. A characteristic symptom of bacterial canker is bird’s eye spots which occur on fruits and reduce their quality. The spots are white to yellow and about 3 to 4 mm in diameter with raised light brown centers (2).

Ecology and Spread

Clavibacter michiganensis subsp. michiganensis can be present in the seed, transplants, and production areas. When seedborne, the pathogen can be present both on the outside of the seed as well as beneath the seed coat (1). It may survive on the seed coat for up to five years (7). This allows long distance spread of the disease via infected seeds and transplants. Secondary spread can occur by means of plant debris, weed hosts, infected seedlings, contaminated equipment, overhead irrigation, rain, and cultural operations such as pruning and leaf removal. The pathogen enters the plant through the stomates and wounds in leaves and roots (1). Disease development is favored by warm temperatures (75 to 90 degrees Fahrenheit) and with high moisture or relative humidity. The host range of Clavibacter michiganensis subsp. michiganensis is limited to members of the plant family Solanaceae (4).

Geographic Distribution

EPPO region

Austria, Belarus, Belgium, Bulgaria, Czech Republic, Egypt, Finland, France, Germany, Greece, Hungary, Ireland, Israel, Italy, Lebanon, Lithuania, Morocco, Netherlands, Norway, Poland, Portugal, Romania, Russia, Slovenia, Spain, Switzerland, Tunisia, Turkey, United Kingdom, Ukraine, Yugoslavia.

Asia

Armenia, Azerbaijan, China, India, Iran, Israel, Japan, Lebanon, Turkey.

Africa

Egypt, Kenya, Madagascar, Morocco, South Africa, Tunisia, Togo, Uganda, Zambia, Zimbabwe

North America

Canada, United States of America (California, Florida, Georgia, Hawaii, Iowa, Illinois, Indiana, Michigan, North Dakota, Ohio, Wyoming), Mexico.

Central America and Caribbean

Costa Rica, Cuba, Dominica, Dominican Republic, Grenada, Guadeloupe, Martinique, Panama.

South America

Argentina, Brazil, Chile, Colombia, Ecuador, Peru, Uruguay.

Oceania

Australia, New Zealand, Tonga.

Management

Management of any pathogen is often dependent upon both cultural and chemical options. Consult your local extension specialist or agent for recommendations relevant to your particular host and state. Remember: the label is the law.

Diagnostic Procedures

Recognizing symptoms of the disease is important for determining what procedures to follow to identify the pathogen causing disease development. For symptomatic tomato plants, initial diagnostic measures consist of isolating infected tissues on non-selective and semi-selective media followed by confirmatory procedures to detect Clavibacter michiganensis subsp. michiganensis. These include enzyme-linked immuno assay (ELISA), immunostrips, and polymerase chain reaction (PCR).

Procedures/Media	Result for Clavibacter michiganensis subsp. michiganensis
KOH test	Negative; no stringing is observed (Gram-positive)
Oxidase	Negative; no color change
Urease	Negative; no color change
Kings medium B	Negative; nonfluorescent
Nutrient agar	Fluidal yellow colonies
Yeast extract-dextrose CaCO3 medium	Fluidal and mucoid yellow colonies
Sucrose peptone agar	Positive; colonies are mucoid
Hypersensitive Response	Tomato: Negative; no reaction
	Tobacco: Positive; necrotic area
Miller-Schroth medium	No color change
Crystal violet pectate medium	Negative; pitting is not observed
Arginine Dihydrolase	Negative; no color change
Aerobe-anaerobe test	Aerobic; bacterial growth only at top

ELISA

Immunostrips

Polymerase Chain Reaction

Burokiene, D. (2006). Early detection of Clavibacter michiganensis subsp. michiganensis in tomato seedlings. Agronomy Research, 4(Special), 151-156.

Selected References

1. Blancard, D.. 1995. A Colour Atlas of Tomato Diseases: Observation, Identification and Control. Manson Publications, London. 109-11.

2. CABI and EPPO. Data Sheets on Quarantine Pest: Clavibacter michiganensis subsp. michiganensis. European Plant Protection Organization. Online: http://www.eppo.int/QUARANTINE/bacteria/Clavibacter_m_michiganensis/CORBMI_ds.pdf.

3. Eichenlaub, R., and Gartemann, K. The Clavibacter michiganensis subspecies: molecular investigation of gram-positive bacterial plant pathogens. Annual Review of Phytopathology 49:445-464.

4. Gleason, M. L., Gitaitis, R. D., and Ricker, M. D. Recent progress in understanding and controlling bacterial canker of tomato in eastern North America. Plant Disease 77:1069-1076.

5. Jones, J. B. 1991. Compendium of Tomato Diseases. The American Phytopathological Society, St. Paul, MN. 25-26.

6. Kado, C. I. 2010. Plant Bacteriology. American Phytopathological Society, St. Paul, Minnesota.. 131-35.

7. Plant Science and Landscape Agriculture Extension. Managing Bacterial Canker in Tomato: Key Strategies. Integrated Pest Management Program. Online: http://ipm.uconn.edu/documents/raw2/Managing%20Bacterial%20Canker%20in%20Tomato/Managing%20Bacterial%20Canker%20in%20Tomato.php?display=print.

8. Soil, Crop, & Pest Management. Bacterial Canker. University of Massachusetts Amherst. Online: http://extension.umass.edu/vegetable/diseases/bacterial-canker.

Acknowledgements

• National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2011-41530-30708 as part of "Diagnostic Image Series Development for Supporting IPM in the Southern Region" (USDA-NIFA-RIPM-003351)