RalstoniaRalstonia solanacearumsolanacearum R3B2,R3B2,Significant Events of this Significant Events of this

Select AgentSelect AgentKaren Karen SnoverSnover--CliftClift

Associate Director, NEPDNAssociate Director, NEPDNDirector, Plant Disease Diagnostic Clinic, Cornell UniversityDirector, Plant Disease Diagnostic Clinic, Cornell University

The Disease and Hosts

• The bacterium Ralstoniasolanacearum Race 3 Biovar 2 causes diseases commonly known as Southern Wilt or Brown Rot

• Southern Wilt is a disease of Geranium and Brown Rot is a disease of Potato Photo Scott Bauer, USDA-ARS

• Ralstonia solanacearum Race 3 Biovar 2 has appeared on Geranium a few times in recent years but it appears to be confined to greenhouse crops and there is no evidence of spread to potato, tomato, or eggplant

Photo Peggy Greb, USDA-ARS

Why a Select Agent?• Ralstonia solanacearum R3B2 was deemed a select agent due to

its ability to survive in temperate climates and due to its ability to infect potato and other solanaceous plants.

Races and Biovars of Ralstonia solanacearum

Race Host Range Geog. Distribution Biovar

1Wide Asia, Australia,

Americas3, 41

2 BananaOther Musa spp.

Caribbean, BrazilPhilippines

1

3 Potato, some other Solanaceae,Geranium; plusa few other species.

Worldwide except US and Canada

2

4 Ginger Asia 3, 4

5 Mulberry China 5(Daughtrey, 2003 Reprinted, with slight modification, from Denny and Hayward, 2001)

Foliar WiltingBacterial Ooze

(Photos Margery Daughtrey, Cornell University)

Stem Necrosis

Symptoms

Foliar Wilting

Bacterial Ooze

(Photos Central Science Laboratory, Crown Copyright)

Soil Adhesion

Symptoms

(Photo: Caitlin Allen, University of Wisconsin)

(Photos Central Science Laboratory, Crown Copyright)

Development ofRalstonia solanacearum diseases

• Primarily a soilborne pathogen that infects through the roots

• Other infection routes include nematode feeding, handling of plant material by greenhouse workers, and natural root development-Wounds.

• Crops may be infected through contaminated potting media and/or contaminated water.

(Photo Rutgers University,Department of Floriculture)

Methods of Diagnosing Rs R3B2 Infections

• Isolation on Semi-Selective Medium• Use of medium selective for Ralstonia

solanacearum• SMSA and/or TZC

• ELISA• Enzyme Linked Immunosorbant Assay• Test takes advantage of the specific binding between

antibodies and antigens• Only specific for Ralstonia solanacearum not R3 B2• Used for initial screening of large quantities of

materials• Carbon Utilization Test

• Differentiates biovars• PCR

• Polymerase Chain Reaction• A method of amplifying specific segments of DNA • Specific for Ralstonia solanacearum R3 B2

History of Southern Wilt of Geranium

Race 3 commonly found throughout the world except for United States and Canada

(Year)

Introduction of Rs R3B2 on geranium cuttings

1999

Introduction of Rs R3B2 on geranium cuttings

2000

No Reported Cases2001

No Reported Cases2002

Introduction on cuttings from Kenya, 127 greenhouses in 27 states

2003

Introduction on cuttings from Guatamala, no additional sites found

2004

Testing but no positives - Yet2005-2006

(Wisconsin Department of Agriculture)

Industry and Regulatory Response• Regulatory officials participated

in an effective eradication program during the 2003 and 2004 introductions.

Badger Tag & Label Corporation

• Eradication efforts at a great expense to greenhouse growers.

• Created Action Plan for handling of suspect samples.

• Cutting producers were trained by US regulatory officials to improve sanitation procedures and to increase the amount of disease testing prior to shipments.

• Cuttings now being tracked by barcodes.

NPDN Response

• First test of the new NPDN system. • Announcements went out to NPDN

members, 2nd indicating confidentiality a must.

• Due to the introduction the Network worked with USDA, APHIS, PPQ personnel to coordinate a diagnostic training session for key diagnosticians across the country.

• The NPDN laboratories were able to improve diagnostic capabilities by providing basic testing for the presence of the pathogen.

Summary

• The outbreak of this pathogen caused increased plant pathology educational programs and increased research efforts.

• Industry learned a lot about the quarantine process and how to prevent the establishment of new pathogens in the United States.

• The threat was successful eradicated with no indication of an escape to potatoes and geranium cutting producers now follow an improved set of sanitation protocols.

• The NPDN laboratories were able to improve diagnostic capabilities and respond faster to disease outbreaks.