Taxonomy

Domain	Bacteria
Phylum	Proteobacteria
Class	Gammaproteobacteria
Order	Enterobacteriales
Family	Enterobacteriaceae
Genus	Pectobacterium
Species	Pectobacterium carotovorum

Scientific Name

Pectobacterium carotovorum ssp. carotovorum

Scientific Name Synonyms

Erwinia carotovora ssp. carotovora

Common Name

bacterial soft rot

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

Reviewed by:Name, Organization

Pathogen

Pectobacterium carotovorum is a gram negative, rod-shaped, non-sporulating facultatively anaerobic bacterium. The bacteria are typically 0.5-1.0 x 1.0-3.0 µm rods that are single-celled and motile with peritrichous flagella. Pectobacterium carotovorum causes the Bacterial Soft Rot (BSR) diseases in many crops and ornamentals, ranging from carrots and potatoes to leafy greens and irises. Primarily, this pathogen causes post-harvest issues for fruits and vegetables (7).

Symptoms and Signs

The main symptoms caused by Pectobacterium carotovorum include wilting and water-soaked lesions, which may lead to stem collapse. Soft rot symptoms may include browning of stem and pith in tomatoes, especially when ripe fruit is infected. Changes develop quickly after stem collapse, such as skin folding and cracking followed by development of creamy white ooze (4). Water-soaked lesions may develop on the outside of fruits and vegetables. Over time, these lesions will sink and may form pits as the bacteria rots away the middle lamella (2). Cuttings from ornamental plants will develop a crown rot that will extend 5 to 10 cm up the stem from the base of the plant. Later in development, vascular infections and stem rot are typically characterized by vascular browning, wilting, darkening, water-soaked stems and leaves, and total plant collapse. These symptoms develop within 24 to 48 hours after infection. Vascular infections that occur when conditions for disease development are not ideal may lead to stunting and yellowing (6). A foul odor can also occur when secondary organisms invade the infected tissues (7).

Ecology and Spread

Pectobacterium spp. are opportunistic pathogens that require certain environmental conditions and a weak or susceptible host in order to cause the soft rot disease (6). Extended periods of soil saturation in the field can facilitate P. carotovorum infection (7). High humidity and heavy rainfall are required for the dispersal of Pectobacterium carotovorum. A typical source of inoculum may be contaminated irrigation water. Other sources include infected plant debris, insects vectoring the pathogen, or using contaminated potting media, tools, and/or soil (6). Soft rot can become an issue during and after harvesting due to improper handling of plant material. Bruising that may occur post-harvest allows for entry of the pathogen. Unsanitary storage facilities may also harbor the pathogen thereby allowing for its introduction into the host (7). Plants injured from fungal diseases are also likely to become infected with P. carotovorum.

The bacterium may penetrate susceptible hosts via wounds in the petiole, which will travel to the stem. This leads to the collapse of the plant (6). The optimum temperature for P. carotovorum is 20 to 25 °C (1,6,7). It can be commonly found in the root zones of various host and nonhost crop and weed species (8). Host range for ornamentals include begonia, ornamental pepper, dahlia hybrids, geranium, African violet, and holiday cactus, among others (6). Umbelliferous crops are all susceptible, as are most vegetables (7).

Geographic Distribution

Pectobacterium carotovorum is found worldwide on all continents, but is more prominent in the following areas:

Europe

Algeria, Austria, Belarus, Belgium, Denmark, Egypt, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Russia (European), Spain, Sweden, Switzerland, United Kingdom, Yugoslavia.

Asia

Bangladesh, China (Fujian, Hunan, Jiangsu, Jiangxi, Zhejiang), India (Bihar, Delhi, Karnataka, Uttar Pradesh, West Bengal), Iran, Israel, Japan (Hokkaido), Korea Democratic People's Republic, Korea Republic, Malaysia (Peninsular), Nepal, Philippines, Sri Lanka, Taiwan.

Africa

Algeria, Comoros, Côte d'Ivoire, Congo, Egypt, Réunion, Sudan, South Africa, Zimbabwe.

North America

United States of America (California, Colorado, Connecticut, Florida, Georgia, Massachusetts, North Carolina, North Dakota, Nebraska, New York, Ohio, Pennsylvania, Texas, Virginia, Wisconsin).

Central America and Caribbean

Aruba, Costa Rica, Cuba, Guadeloupe, Guatemala, Haiti, Honduras, Jamaica, Martinique, Panama, Puerto Rico, St. Lucia.

South America

Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Venezuela.

Oceania

Australia (New South Wales, Queensland, Victoria, Western Australia), Cook Islands, New Zealand, Papua New Guinea, Solomon Islands.

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

Procedures/Media	Result for Pectobacterium carotovorum
KOH test	Positive; stringing is observed (Gram-negative)
Oxidase	Negative; no color change
Urease	Negative; no color change
Kings medium B	Negative; nonfluorescent
Nutrient agar	Cream-colored colonies after 24-48 hours
Yeast extract-dextrose CaCO3 medium	Creamy, light white colonies after 24-72 hours
Sucrose peptone agar	Negative; colonies are not mucoid
Hypersensitive Response	Tomato: Positive; necrotic area
	Tobacco: Positive; necrotic area
Miller-Schroth medium	Medium turns red-orange after 24 hours
Crystal violet pectate medium	Positive; pitting is observed
Arginine Dihydrolase	Negative; no color change
Aerobe-anaerobe test	Facultative anaerobe; medium is cloudy from top to bottom

Selected References

1. Barich, D., ed. 2005. Erwinia carotovora. MicrobeWiki. Kenyon Knowledge.Online: http://microbewiki.kenyon.edu/.

2. Bartz, J. A. 1991. Compendium of Tomato Diseases. American Phytopathological Society, St. Paul, MN. 44-45.

3. Blancard, D. 1992. A Colour Atlas of Tomato Diseases: Observe, Identify, Control. Manson Publishing, London. 105, 129, 155.

4. Blancard, D.,, Lecoq, H., and Pitrat, M. 1994. A Colour Atlas of Cucurbit Diseases: Observation, Identification & Control. Manson Publishing, London.125, 143, 183.

5.CABI and EPPO. Data Sheets on Quarantine Pest - Erwinia chrysanthemi. European Plant Protection Organization. Online: http://www.eppo.int/QUARANTINE/bacteria/Erwinia_chrysanthemi/ERWICH_ds.pdf

6. Daughtrey, M. L., Wick, R. L., and Peterson, J. L. 2006. Compendium of Flowering Potted Plants. The American Phytopathological Society, St. Paul, MN. 49-50.

7. Davis, M. R., and Raid, R. N.. 2002. Compendium of Umbelliferous Crop Diseases. American Phytopathological Society, St. Paul, MN. 14-15.

8. Rowe, R. C., Miller, S. A., and Riedel, R. M. 1995. The Ohio State University Extension Fact Sheet. “Blackleg, Aerial Stem Rot, and Tuber Soft Rot of Potato.” Ohio State University. HYG-3106-95. Online: http://ohioline.osu.edu/hyg-fact/3000/3106.html.

Resources and References

Acknowledgments

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)