Many of the effectors are presumably redundant as individual deletions of effector genes does not impair virulence, however mutations in T3SS apparatus has strong effect. Typically, Xanthomonas T3SS injects a cocktail of 20-30 effector proteins that interfere with plant immune system and various host cellular processes. Xanthomonas possess almost all known secretion systems (types I to VI) that play different roles in the life and disease cycle, with type III secretion system ( T3SS) being the key factor of pathogenicity. Response to light is important in pathogenicity of these bacteria and regulates surface attachment and production of biofilm. Resistance to UV is mostly conferred by genes related to oxidative stress and DNA repair. Xanthomonas produce xanthomonadins - yellow pigments that protect from radiation caused from natural light. Xanthomonas uses surface polysacharides, adhesion proteins and type IV pili to attach to the surface and can form biofilms to sustain abiotic stresses (UV, drought, etc). When population of bacteria increases it re-emerges to the surface and is transmitted mainly by wind, rain or through seeds or agricultural machinery, while animal and insect vectors seems to play minor role. bacteria grow on the aerial tissues of plant host (leaf, fruit, etc) followed by endophytic stage when bacteria enter and colonise host tissues through wounds or natural openings. Infection starts with epiphytic stage – i.e. life cycle Ĭontaminated seeds, weeds, infected plant debris are the main route of transmission. Plant pathogenesis and disease control Xanthomonas spp. oryzae, is a disease found worldwide and particularly destructive in the rice-producing regions in Asia. punicae cause bacterial blight of pomogranate.īacterial blight of rice, caused by Xanthomonas oryzae pv. In some areas where infection begins soon after transplanting, the total crop can be lost as a result of this disease. Causes of this disease include Xanthomonas euvesicatoria and Xanthomonas perforans =, Xanthomonas vesicatoria, and Xanthomonas gardneri. citri is an economically important disease of many citrus species (lime, orange, lemon, pamelo, etc.) īacterial leaf spot has caused significant crop losses over the years. Pathogenic species show high degrees of specificity and some are split into multiple pathovars, a species designation based on host specificity.Ĭitrus canker, caused by Xanthomonas citri subsp. Xanthomonas species can cause bacterial spots and blights of leaves, stems, and fruits on a wide variety of plant species. Xanthomonas plant pathogens Symptoms of diseases caused by Xanthomonas Temperature range – 4 to 37 ☌, optimal growth 25-30 ☌ īiochemical and physiological test results are:.Most produce large amounts of extracellular polysaccharide.Yellow pigment from xanthomonadin, which contains bromine.Mucoid, convex, and yellow colonies on YDC medium.Motility – motile by a single polar flagellum.There is a proposal to reorganize Xanthomonas banana and maize/corn pathotypes along the lines of the most recent phylogenetic data. are evolutionary linked to opportunistic human pathogen Stenotrophomonas maltophilia, that was previously called Xanthomonas maltophilia. More recently, genome-wide analysis of multiple Xanthomonas strains mostly supports the previous phylogenies. While previous research has illustrated the complexity of the genus Xanthomonas, recent research appears to have resulted in a clearer picture. Other tools, including multilocus sequence analysis and amplified fragment-length polymorphism, have been used for classification within clades. Later work using DNA:DNA hybridization has served as a framework for the general Xanthomonas species classification. Xanthomonas was first described as a monotypic genus and further research resulted in the division into two groups, A and B. Dowson later reclassified the bacterium as Xanthomonas campestris and proposed the genus Xanthomonas. The genus Xanthomonas has been subject of numerous taxonomic and phylogenetic studies and was first described as Bacterium vesicatorium as a pathogen of pepper and tomato in 1921. Different species typically have specific host and/or tissue range and colonization strategies. There are at least 27 plant associated Xanthomonas spp., that all together infect at least 400 plant species. Xanthomonas (from greek: xanthos – “yellow” monas – “entity”) is a genus of bacteria, many of which cause plant diseases. Xanthomonas translucens growing on sucrose peptone agar showing yellow pigment
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