Ralstonia solanacearum Race 3 biovar 2 Background photo: USDA APHIS PPQ Archives

Ralstonia solanacearum Race 3 biovar 2 Introduction Hosts Symptoms Transmission Detection Control Photo Jean L. Williams-Woodward, University of Georgia,

Introduction Ralstonia solanacearum Race 3 biovar 2 is a bacterium that causes the following diseases: –Southern Wilt of Geranium –Brown Rot and Bacterial Wilt of Potato –Bacterial Wilt of Tomato and Other Solanaceous Crops This pathogen is designated as a member of the Agricultural Bioterrorism Select Agent List.

Other Ralstonia solanacearum Races and Biovars RaceHost RangeGeographic Distribution Biovar 1WideAsia, Australia, Americas 3,4 1 2Banana Other Musa spp. Caribbean,Brazil Philippines 1 3Potato, some other Solanaceae, Geranium; Worldwide except US and Canada 2 4GingerAsia3,4 5MulberryChina5 (Daughtrey, 2003 Reprinted, with slight modification, from Denny and Hayward, 2001)

Global Distribution World wide losses from bacterial wilt on potato crops are more than $950 million per year (Allen 2003). Outbreaks of R. solanacearum Race 3 biovar 2 have occurred throughout Europe in recent years. These outbreaks are thought to be the result of imports of infected plant material from locations where the disease is already established (Janse 1996). Photo H.D. Thurston, Cornell University, fieldtrip.cornell.edu/docthurston/Thumbs%20- %20Brown%20Rot/Brown%20Rot.html

History in United States (Year) Race 3 commonly found throughout the world except for United States and Canada Introduction of Rs R3b2 on geranium cuttings 1999 Introduction of Rs R3b2 on geranium cuttings 2000 No Reported Cases 2001 No Reported Cases 2002 Detection on cuttings from Kenya, 127 greenhouses in 27 states 2003 Detection on cuttings from Guatemala, no additional sites found Testing but no positives - Yet Photo Peggy Greb, USDA-ARS

Hosts Hosts of Ralstonia solanacearum Race 3 biovar 2 include several solanaceous plants: –Potato –Tomato –Eggplant –woody nightshade Geranium (Pelargonium spp.) can also serve as a host. Photo H.D. Thurston, Cornell University, fieldtrip.cornell.edu/docthurston/Thumbs%20- %20Brown%20Rot/Brown%20Rot.html

Symptoms on Geraniums Yellowing, wilting and browning of lower leaves Vascular discoloration and necrosis of the stem Brown discoloration of the roots Photos Margery Daughtrey, Cornell University,

Signs on Geraniums Bacterial Ooze Bacterial streaming: cut stem or petiole placed in water should display cloud generated from bacterial streaming out of plant tissue Bacterial ooze Photo Margery Daughtrey, Cornell University, Photo David B. Langston, University of Georgia, Bacterial Streaming

Signs and Symptoms on Potato Plants Foliage Stunting Yellowing Wilting, initially limited to top of plant Stem Vascular discoloration Collapse in young plants Bacterial ooze Bacterial streaming Photos H. David Thurston, Cornell University, fieldtrip.cornell.edu/docthurston/Thumbs%20- %20Brown%20Rot/Brown%20Rot.html

Signs and Symptoms on Potato Tubers Bacterial ooze, which in later stages may emerge from eye and heel Discoloration of the vascular ring Photo Plant Protection Service Archives, Netherlands, Photo Central Science Laboratory, Harpenden Archives, British Crown, United Kingdom, Bacterial Ooze

Signs and Symptoms on Tomatoes Wilting Vascular discoloration Bacterial ooze Photos Clemson University - USDA Cooperative Extension Slide Series, Vascular Discoloration Vascular Discoloration Images are of Ralstonia solanacearum Race 1 not Race 3. Symptoms of Race 3 biovar 2 on tomato can be similar.

Transmission Contaminated soil, irrigation water, surface water, equipment and personnel Pathogen may enter plants via wounds from handling or nematode feeding Photo Anson Eaglin, USDA-APHIS,

Transmission Infected plant material –In geraniums: spread through the use of infected cuttings –In potatoes: spread through infected potato seed stock Photo by Peggy Greb, USDA-ARS, s/jan03/k htm

Detection and Diagnosis Isolation on Semi-Selective Medium –Use of medium selective for R. solanacearum not to Race or biovar ELISA –Only specific for Ralstonia solanacearum not Race and biovar –Used for initial screening of large quantities of materials The diagnosis to Race and biovar can be difficult often requiring several diagnostic tests to make a final diagnosis. Photo Tom Creswell, NCSU, Culture of R. solanacearum on TZC semi-selective medium

Detection and Diagnosis Testing to Determine Race and Biovar –Carbon Utilization Testing (used to differentiate biovar) –Real Time PCR (used to differentiate Race) Real-time PCR used for determination of race of R. solanacearum. (Photo Dawn Dailey- O’brien, Cornell University)

Control: Potato No chemical control available Removal of weed hosts such as woody nightshade which is thought to act as a reservoir for inoculum Altering soil pH over the course of the growing season Screening tubers for disease before planting in the field Rotation with non- susceptible crops Photo Joel Floyd, USDA APHIS PPQ, Woody nightshade can serve as a host for R. solanacearum Race 3 Biovar 2 and a source of inoculum for potato crops

Control: Tomato Plant derived chemical: Thymol has been used as a pre-plant soil fumigant with some success (Momol 2006). Plant breeding efforts have resulted in some tomato breeds with high resistance but also some undesirable traits like small fruit (Momol 2006). Photo Keith Weller, USDA-ARS, htm

Control: Geranium No chemical control available Control relies on eradication of infected plants and proper sanitation practices –Limit greenhouse access and practice good sanitation techniques –Water monitoring for presence of pathogen –Clean irrigation system on a regular basis –Culture index plant material 1-3 years to ensure it is disease free –Practice weed control programs within and around greenhouses Photo © Br. Alfred Brousseau, Saint Mary's College, USDA-APHIS-PPQ Pest Data Sheet Ralstonia solanacearum Race 3 Biovar 2 Lemay et al. 2003

References Allen, C Bacterial Wilt Disease & Ralstonia solanacearum. Talk from 2003 Ralstonia Solanacearum race 3 biovar 2 Outbreak in Geraniums: A Program Review meeting held June 17 and 18, 2003 in Riverdale, MD. Daughtrey, M New and Re-emerging Diseases in Department of Plant Pathology, Cornell University, Long Island Horticultural Research & Extension Center. Denny, T. P. and Hayward, A.C Ralstonia, pages in: Schaad, N. W. et al. Laboratory guide for the identification of plant pathogenic bacteria, 3rd ed. APS Press, St. Paul, 373 pp. Elphinstone, J. and Harris, R Monitoring and control of the potato brown rot bacterium in irrigation water. British Potato Council report Accessed 2004 January 8. Elphinstone, J. January Personal communication. EC project number: SMT project CT Harris, D. C Intra-specific variation in Pseudomonas solanacearum. Pages in: Proc. Int. Conf. Plant Pathog. Bact., 3rd. Janse, J Potato Brown rot in western Europe – history, present occurrence and some remarks on possible origin, epidemiology and control strategies. Bulletin OEPP/EPPO 26: Kim, S. H., Olson, R. N. and Schaad, N Ralstonia solanacearum Biovar 2, Race 3 in geraniums imported from Guatemala to Pennsylvania in Plant Disease 92:S42. Kim, S. H., T. N. Olson, N. W. Schaad, and G. W. Moorman Ralstonia solanacearum Race 3, Biovar 2, the Causal Agent of Brown Rot of Potato, Identified in Geraniums in Pennsylvania, Delaware, and Connecticut. Plant Disease Page 87:4. Lemay, A., Redlin, S., Fowler, G., Dirani, M. 2003, February 12. Pest Data Sheet Ralstonia solanacearum race 3 biovar 2. USDA/APHIS/PPQ Center for Plant Health Science and Technology Plant Epidemiology and Risk Analysis Laboratory Raleigh, NC. Momol, T. 2006, October 12. Recovery Plan for Ralstonia solanacearum Race 3 biovar 2, Causing Brown Rot of Potato, Bacterial Wilt of Tomato and Southern Wilt of Geranium. National Plant Disease Recovery System. Accessed 2006 October O’Hern, C January 5. Detection of Ralstonia solanacearum race 3 biovar 2 in New York Greenhouse (document by Richard Dunkle) [Distribution list]. Accessed 2004 January 5. USDA-ARS Plant Health Division Potato Brown Rot (RALSTONIA SOLANACEARUM) Report on monitoring and eradication in England Defra, Plant Health Division. Accessed 2004 January 8. Williamson, L., Nakoho, K., Hudelson, B. and Allen, C Ralstonia solanacearum race 3, biovar 2 strains isolated from geranium are pathogenic on potato. Plant Dis. 86:

Additional Websites A list of federal, state, university, international, and organization websites about Ralstonia solanacearum Race 3 biovar 2 can be found at the USDA, National Agricultural Library, National Invasive Species Information Center obes/bacterialwilt.shtml

Acknowledgements Editorial Review Margery Daughtrey, Cornell University Long Island Horticulture and Extension Center Dr. Tim Momol, University of Florida, North Florida Research and Education Center

Authors Mary M. McKellar, Cornell University, NEPDN Training Karen Snover-Clift, Cornell University, NEPDN Associate

Publication Details This publication can be used for non-profit, educational use only purposes. Photographers retain copyright to photographs or other images contained in this publication as cited. This material was developed as a topic-based training module for NPDN First Detector Training. Authors and the website should be properly cited. Images or photographs should also be properly cited and credited to the original source. Publication Number: 020 Publication Date: April 19, 2007