A century of phytobacteriology: Old and new questions about bacterial wilt. C. Allen
Department of Plant Pathology, University of Wisconsin, Madison, WI.
Phytopathology 98:S190.

Abstract: In 1896 Erwin F. Smith used Koch’s Postulates to show that Bacillus solanacearum causes bacterial wilt disease of tomato and potato. In the next few decades, researchers focused on understanding how the pathogen survives, infects, and induces wilting on such a wide range of hosts. Early 20th-century plant pathologists asked how B. solanacearum survived without host plants; did it latently infect weeds or native plants, or multiply in water? How did the bacterium form the latent infections that threatened vegetatively propagated hosts like potato and banana? What explained the extreme heterogenity of the species, and its rapid loss of virulence in culture? Finally, what was the mechanism of wilting – did the bacterium produce a toxin injurious to the plant or simply obstruct the xylem vessels? Although we have partial answers to some of these questions, most, such as the mechanisms underlying variability, wilting and latent infections, are still actively studied. The epidemiology of Ralstonia solanacearum (as it is now known) remains poorly understood, and most wilt disease control methods would be familiar to E. F. Smith. Genomic-level analyses combined with in planta imaging and gene expression monitoring are allowing us to address old questions in a systematic, integrated way. Using these tools to study the pathogen in natural hosts, we hope to better understand the environment this bacterium experiences inside its host plants, and the tools it uses to succeed there.