Ralstonia solanacearum (Smith, Yabuuchi et al.)
Significance: Researchers in the United States have recently conducted studies to compare the cold tolerance of different strains of Ralstonia solanacearum (Rs). This bacterium has a wide host range and is responsible for many important plant diseases, including potato brown rot. The research results indicate that Rs strains, when tested in water, vary in their ability to survive exposure to 4oC. Surprisingly some race 1 strains of Rs from the southern United States were shown to be more cold tolerant than exotic R3B2 strains, the latter of which were formerly believed to be more cold tolerant than other strain groups. In another study, host plants were drench inoculated with different strains of Rs and then incubated at 18oC and 30oC. The study results suggested that some Rs strains from the United States (i.e., race 1) may possess an ability similar to R3B2 in terms of causing plant death in colder areas of the world.
Issues of Concern: Although somewhat limited in nature and based on testing done under controlled conditions, these recent studies do suggest that other strain groups already present within North America may pose a threat to host crops in cooler areas.
Dennt, T. P., A.S. Milling, V. G. Bhakta, and C. Allen. 2007. Ralstonia solacearum race 3 biovar 2 strains are not uniquely cold tolerant in vitro. Phytopathology Vol. 97 (7, July, Supplement), page S28.
Norman, D.J., J.Y. Yuen, A. Mangravita-Novo, P.Y. Duan, and D.W. Gabriel. 2007. Variation in pathogenicity of Ralstonia solanacearum strains in relation to their ability to cause disease during periods of cold temperature. Phytopathology Vol 97(7, July Supplement), page S85.