Reclassification of Xanthomonas

Abstract

A comprehensive DNA-DNA hybridization study was performed by using 183 strains of the genus Xanthomonus. This genus was shown to comprise 20 DNA homology groups which are considered genomic species. Four groups corresponded to the previously described species Xanthomonas albilineans, Xanthomonas fiagariae, Xanthomonas oryzae, and Xanthomonas populi. The previously described species Xanthomonas campestris was heterogeneous and was divided into 16 DNA homology groups. One of these groups exhibited a high level of DNA homology with Xanthomonas axonopodis. The 62 pathovars represented in this study were. allocated to appropriate species. Our results, together with previous taxonomic data, supported a comprehensive revision of the classification of the genus Xanthomonas. The species X. albilineans, X. jiagarke, X. oryme, and X. populi are not affected. The type species of the genus,X. campestris (Pammell895) Dowson 1939, is emended to include only the pathovars obtained from crucifers (i.e., X. campestris pv. aberrans, X. campestris pv. armoraciae, X. campestris pv. barbareae, X. campestris pv. campestris, X. campestris pv. incanae, and X. campestris pv. raphani). vesicatoria. Differentiating characteristics were determined for the new species on the basis of metabolic activity on a range of carbon substrates by using the Biolog GN microplate system. X. axonopodisIn the past, the taxonomy of bacteria has been dominated by a phenetic approach, and many classification systems have been and still are based on what were thought to be important phenotypic properties. The taxonomy of the genus Xanthomonas has followed this tendency in that a single phenotypic feature, host specificity, has determined the classification of the genus. Since the first report of a xanthomonad (55) until 1974, it was common practice to define a plant-pathogenic xanthomonad isolated from a new host plant as a new Xanthomonas species. The unreasonable number of nomenspecies resulting from this practice was drastically reduced by Dye and Lelliott (19), who justified their reclassification by referring to the impossibility of differentiating nomenspecies by any feature other than host specificity (10,17). Later, names of former nomenspecies were preserved in a special-purpose classification (18) as Xanthomonas campestris pathovar names.The original classification of the genus Xanthomonas, in which all of the phytopathological variants of X campestris were recognized as separate species, was not sound taxonomically. With the exception of the ambiguous feature of host specificity, few biochemical and phenotypic characteristics were used to differentiate the species. In the last few years, * Corresponding author. Mailing address: Laboratorium voor Microbiologie, Universiteit Gent, Ledeganckstraat 35, B-9000 Ghent, Belgium.workers have provided evidence that the current classification, in whichX. campestris contains more than 140 pathovars, is not a reflection of genomic relationships. The first DNA hybridization experiments performed with Xanthomonas...

Genetic Diversity and Pathogenicity of Xanthomonas axonopodis Strains Inducing Citrus Canker Disease in Iran and South Korea

“…Pathotypes A, B, C, D and E of X. axonopodis could be differentiated through their host ranges and pathogenicity. In our study these pathotypes could be differentiated but forms B, C and D are very closely related to each other and well separated from forms A and E. These results support the previous results published by Vauterin et al [23,24]. These pathotypes have at least one or more unique sites on their genomes which can differentiate them from each other.…”

“…aurantifolii and E or X. a. pv. citrumelo [23,24]. Of these pathotypes form A which causes true or Asiatic canker disease is the most devastating form and can infect most commercial citrus varieties and citrus relatives [19,21,23].…”

Identification of a host 14-3-3 protein that interacts with Xanthomonas effector AvrRxv

“…vescicatoria or X. euvesicatoria) is the causal agent of bacterial spot disease in both pepper and tomato [1,2]. Xcv strains carrying the avirulence gene avrRxv elicit resistance, characterized by localized necrosis referred to as the hypersensitive response (HR), in the tomato cultivar Hawaii 7998 [3].…”

Rizobactérias no controle da mancha angular do algodoeiro

“…Dentre as doenças que ocorrem no algodão, a mancha angular, Xanthomonas axonopodis pv. malvacearum (Smith) (VAUTERIN et al, 1995) (Xam), a ramulose (Colletotrichum gossypium var. cephalosporioides A. S. Costa) estão disseminadas, praticamente, em todas as áreas de cultivo no país.…”