Ralstonia solanacearum Race 3, Biovar 2 Strains Isolated from Geranium Are Pathogenic on Potato

Abstract

Ralstonia solanacearum race 3, biovar 2 is a soilborne bacterium that causes potato brown rot disease in temperate and subtropical climates. Recent outbreaks of this disease in Europe have caused serious losses, but the pathogen had not been identified in the United States. However, in 1999, strains of R. solanacearum were isolated from wilting geraniums growing in Wisconsin greenhouses. Physiological and biochemical tests of the Wisconsin strains and a similar strain from South Dakota demonstrated that the strains belong to R. solanacearum subgroup biovar 2, which is largely synonymous with the race 3 subgroup, a classification based on host range. These results were confirmed by polymerase chain reaction analyses in which race 3, biovar 2-specific primers amplified a fragment of the expected size. This is the first report of race 3, biovar 2 in the United States, and it is the first known occurrence of race 3, biovar 2 in Wiscon-sin. The geranium strains were highly pathogenic on both geranium and potato. The presence of R. solanacearum race 3, biovar 2 in the United States raises concern that the bacterium could move from ornamental plants into potato fields, where it could cause both direct economic damage and quarantine problems. A commercial indirect enzyme-linked immunosorbent assay for R. solanacearum produced some false negatives for these strains, indicating that current indexing may not be sufficient to identify this destructive pathogen.

In Vitro Evaluation of Antibacterial Chemicals and Bioagents against Ralstonia solanacearum Infecting Bacterial Wilt in Ginger

“…The inoculated plant lost turgidity; leaves started dropping and plant wilted suddenly (Fig.4). Pathogenicity of R. solanacearum causing bacterial wilt was proved earlier by several workers (Winstead and Kelman, 1952;Schell M. A., 2000;Williamson et al, 2002;Rajan et al, 2002;Kumar and Sarma, 2004;Umesha et al, 2005;Hikichi, 2007;Rashmi et al, 2012;Artal, 2012;Thomas and Upreti, 2014;Zulperi et al, 2014). Kumar A.…”

Ralstonia solanacearum Needs Flp Pili for Virulence on Potato

“…Virulence tests of R. solanacearum strains were conducted on susceptible potato plants, as described by Liu et al (2001), except that the plants were not watered for 24 h prior to inoculation (Williamson et al 2002). Potato plants (30-day-old, 15 cm in height) were inoculated by drenching the soil (0.5 kg) in 20-cm pots with 50 ml of the bacterial suspension (10 8 CFU/ml) or by applying 5 µl of the inoculum to the stub of freshly severed leaf petioles.…”

Plant Pathogen Forensics: Capabilities, Needs, and Recommendations

“…This race of the wilt bacterium was inadvertently introduced at least twice in recent years into the United States via infected geraniums shipped from Africa and Central America to nurseries (90,191). "Suspect" geraniums were quarantined and eradicated, and several nursery growers were forced out of business.…”