Phytopathogenic Bacteria

A few hundred bacterial species, belonging to the Proteobacteria, Mollecutes and Actinomycetes cause a large number of different plant diseases, some of which are devastating for agricultural crops. Symptoms of bacterial plant diseases are diverse and include necrosis, tissue maceration, wilting, and hyperplasia. For successful infection to occur, the pathogen must overcome plant defense mechanisms, which it often does by injecting effector molecules directly into plant cells to suppress a host response. Virulence may also involve production of plant cell wall-degrading enzymes, toxins and/or plant hormones often under control of quorum sensing mechanisms. Some phytopathogenic bacteria actively move to their host via chemotaxis and enter the plant through natural openings such as stomata and lenticels or wounds caused by insect feeding, fungal infection, or mechanical plant damage. Host plants are internally colonized locally through intercellular spaces and systemically via the vascular system. Control of bacterial plant diseases is achieved mainly by prevention and exclusion of the pathogen since there are few effective chemical control agents and sources of resistance against bacterial diseases are limited.