Reclassification of the xanthomonads associated with bacterial spot disease of tomato and pepper.

Four phenotypic xanthomonad groups have been identified that are pathogenic to pepper, tomato, or both hosts. These include groups A and C which are found in Xanthomonas axonopodis pv. vesicatoria, group B found in X. vesicatoria, and group D found in 'X. gardneri'. We present DNA:DNA hybridization data in which X. axonopodis pv. vesicatoria group A and C strains have less than 70% DNA relatedness with each other, with the type strain of X. axonopodis, and with the currently classified species within Xanthomonas and, therefore, should be removed from this species and given species status. We present information that the A strains most closely resemble the strains originally isolated by Doidge in 1921. In an attempt to avoid confusion in nomenclature as stated in Principle 1 of the Bacteriological Code, we propose that the A strains of X. axonopodis pv. vesicatoria be renamed as X. euvesicatoria (ATCC11633T= NCPPB2968T = ICMP 109T = ICMP 98T). Use of the euvesicatoria epithet should be reserved for strains originally identified by Doidge, which she designated Bacterium vesicatorium  in the original description when she referred to those strains as being feebly amylolytic. The name X. perforans sp. nov. is proposed for the C group of strains previously designated as X. axonopodis pv. vesicatoria (ATCC BAA-983T = NCPPB 4321T). We also propose that 'X. gardneri', which has less than 70% DNA relatedness with any of the Xanthomonas species and which has never had taxonomic status, be named X. gardneri (ATCC 19865T = NCPPB 881T) to reflect the specific epithet proposed by Sutic in 1957.

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title: A proposed nomenclature and classification for plant pathogenic bacteria
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title: Towards An Improved Taxonomy of Xanthomonas
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title: Two genetically diverse groups of strains are included in Xanthomonas campestris pv. vesicatoria.
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title: Proteins unique to phenotypically distinct groups of Xanthomonas campestris pv. vesicatoria revealed by silver staining
abstract: Silver staining of sodium dodecyl sulfate-lysed cells of Xanthomonas campestris pv. vesicatoria electrophoretically separated in polyacrylamide gel revealed broad, dark gray bands in the low molecular weight region. The molecular weight of these bands was characteristic for each of the two major phenotypic groups identified in our X. c. vesicatoria collection. A 32- to 35-kDa band, designated a, was present in 192 of 197 tomato race 1 strains; whereas, a 25- to 27-kDa band, designated β, was present in all 55 strains of tomato race 2. Race 1 strains expressing an a band were unable to hydrolyze starch (Amy - ), and very few degraded pectate (Pec - ). In contrast, most race 2 strains were Amy + and Pec + [...]

title: Systematic analysis of xanthomonads (Xanthomonas spp.) associated with pepper and tomato lesions.
abstract: The taxonomy and evolutionary relationships among members of the genus Xanthomonas associated with tomato and pepper have been a matter of considerable controversy since their original description in 1921. These bacteria, which are a major affliction of tomato and pepper crops in warm and humid regions, were originally described as a single species, but subsequent research has shown the existence of at least two genetic groups differentiated by physiological, biochemical and pathological characteristics. This work synthesizes the findings from several approaches, including pathogenicity tests, enzymic activity, restriction fragment analysis of the entire genome, DNA-DNA hybridization and RNA sequence comparisons based on a 2097 base sequence comprising the 16S rRNA gene, the intergenic spacer located between the 16S and 23S rRNA genes and a small region of the 23S rRNA gene. Within the group of xanthomonads pathogenic on pepper and tomato four distinct phenotypic groups exist, of which three form distinct genomic species. These include Xanthomonas axonopodis pv. vesicatoria (A and C group), Xanthomonas vesicatoria (B group) and Xanthomonas gardneri (D group). On the basis of phenotypic and genotypic differences between A- and C-group strains, the C strains should be considered as a subspecies within Xanthomonas axonopodis pv. vesicatoria.

title: Reclassification of Xanthomonas
abstract: A comprehensive DNA-DNA hybridization study was performed by using 183 strains of the genus Xanthomonas. 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 fragariae, 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. fragariae, X. oryzae, and X. populi are not affected. The type species of the genus, X. campestris (Pammel 1895) 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). X. axonopodis Starr and Garces 1950 is emended to include 34 former X. campestris pathovars. The following species names are proposed: Xanthomonas arboricola sp. nov., including X. arboricola pv. corylina, X. arboricola pv. juglandis, X. arboricola pv. poinsettiicola (type C strains of the former X. campestris pathovar), X. arboricola pv. populi, and X. arboricola pv. pruni; Xanthomonas bromi sp. nov. for strains isolated from bromegrass; Xanthomonas cassavae (ex Wiehe and Dowson 1953) sp. nov., nom. rev.; Xanthomonas codiaei sp. nov., including type B strains of the former taxon X. campestris pv. poinsettiicola; Xanthomonas cucurbitae (ex Bryan 1926) sp. nov., nom. rev.; Xanthomonas hortorum sp. nov., including X. hortorum pv. hederae, X. hortorum pv. pelargonii, and X. hortorum pv. vitians; Xanthomonas hyacinthi (ex Wakker 1883) sp. nov., nom. rev.; Xanthomonas melonis sp. nov.; Xanthomonas pisi (ex Goto and Okabe 1958) sp. nov., nom. rev.; Xanthomonas sacchari sp. nov. for strains isolated from diseased sugarcane in Guadeloupe; Xanthomonas theicola sp. nov.; Xanthomonas translucens (ex Jones, Johnson, and Reddy 1917) sp. nov., nom. rev., including X. translucens pv. arrhenatheri, X. translucens pv. cerealis, X. translucens pv. graminis, X. translucens pv. hordei, X. translucens pv. phlei, X. translucens pv. phleipratensis, X. translucens pv. poae, X. translucens pv. secalis, X. translucens pv. translucens, and X. translucens pv. undulosa; Xanthomonas vasicola sp. nov., including X. vasicola pv. holcicola and X. vasicola pv. vasculorum (type B strains of the former taxon X. campestris pv. vasculorum); and Xanthomonas vesicatoria (ex Doidge 1920) sp. nov., nom. rev., which includes the type B strains of the former taxon X. campestris pv. 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.

title: A third tomato race of Xanthomonas campestris pv. vesicatoria
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title: Physiological, chemical, serological, and pathogenic analyses of a worldwide collection of Xanthomonas campestris pv. vesicatoria strains.
abstract: Xanthomonas campestris pv. vesicatoria strains from a worldwide collection were assigned to the A or B group by testing for amylolytic activity and the presence of the α or β protein band. Cluster analyses of serological, carbon substrate utilization, and fatty acid composition data resulted in dendrograms with interspersed clusters of A and B strains, suggesting that the strain populations within each group are heterogeneous. However, further analysis of the data identified features unique to members of each group. Two monoclonal antibodies reacted only with group A strains, and two reacted only with group B strains. Reactivity patterns further subdivided each group into three serovars [...]