904947
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 (Ann. Appl. Biol. 7: 407-430, 1921) 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.
82322108
Bacterial spot of tomato.
What does bacterial spot look like? Bacterial spot can affect all above ground parts of a tomato plant, including the leaves, stems, and fruit. Bacterial spot appears on leaves as small (less than 1⁄8 inch), sometimes water-soaked (i.e., wet-looking) circular areas. Spots may initially be yellow-green, but darken to brownish-red as they age. When the disease is severe, extensive leaf yellowing and leaf loss can also occur. On green fruit, spots are typically small, raised and blister-like, and may have a yellowish halo. As fruit mature, the spots enlarge (reaching a maximum size of 1⁄4 inch) and turn brown, scabby and rough. Mature spots may be raised, or sunken with raised edges. Bacterial spot symptoms can be easily confused with symptoms of another tomato disease called bacterial speck. For more information on this disease, see University of Wisconsin Garden Facts XHT1250.
85290688
A proposed nomenclature and classification for plant pathogenic bacteria
Abstract Many names of plant pathogenic bacteria will not be included in the Approved Lists, 1980, if the lists contain only the names of valid species. It is proposed that pathogens which do not have a claim to species rank be classified as pathovars. All validly published names of plant pathogens for which there are authentic cultures are listed here as species or as pathovars. A guide for using the term pathovar at the infrasubspecific level is suggested. Designated type and reference strains are listed, and neotype and new reference strains are suggested where none has been reported elsewhere.
86087869
Towards An Improved Taxonomy of Xanthomonas
Improvement of the taxonomy of the genus Xanthomonas and especially of Xanthomonas campestris, which is subdivided into more than 125 pathovars, is discussed. Recent contributions to the taxonomy of Xanthomonas are reviewed, and on the basis of these data and unpublished data from several laboratories, the usefulness of different phenotypic, chemotaxonomic, and genotypic techniques is discussed. The heterogeneity of several X. campestris pathovars has been demonstrated by sodium dodecyl sulfate electrophoresis of whole-cell proteins and fatty acid fingerprinting. The host selectivity of the pathovars is not correlated with their relationships as revealed by DNA-DNA hybridization experiments. In order to reveal the phylogenetic relationships among X. campestris pathovars and their relationships to other Xanthomonas species, it will be necessary to perform extensive DNA-DNA homology studies as an essential part of a polyphasic approach. At present, six DNA homology groups within X. campestris have been delineated. A systematic approach to improve the taxonomy of the genus Xanthomonas is proposed.
85164097
Two genetically diverse groups of strains are included in Xanthomonas campestris pv. vesicatoria.
Two genetically diverse groups of strains were identified among cultures of Xanthomonas campestris pv. vesicatoria isolated from plants with bacterial spot of pepper and tomato. Group A strains do not pit pectate gels or hydrolyze starch, whereas group B strains are strongly positive for these reactions. Group A strains cause a hypersensitive reaction in plants of tomato breeding line Hawaii 7998, but group B strains do not. Other differences between the two groups of strains were discovered in tests for utilization of carbon compounds, serology, fatty acid profiles, silver-stained protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels, and DNA restriction enzyme digestion profiles. The levels of DNA homology between strains belonging to the same group were more than 74%, but the levels of DNA homology between strains belonging to different groups were less than 46%. The two groups of strains have different genetic backgrounds, but cause essentially the same disease of tomato and pepper.
86462555
Proteins unique to phenotypically distinct groups of Xanthomonas campestris pv. vesicatoria revealed by silver staining
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 + [...]
17323567
Systematic analysis of xanthomonads (Xanthomonas spp.) associated with pepper and tomato lesions.
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.
85743291
Reclassification of Xanthomonas
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.
84688539
A third tomato race of Xanthomonas campestris pv. vesicatoria
Strains of Xanthomonas campestris pv. vesicatoria were isolated from several tomato fields in Florida that differed from tomato race 1 (T1) strains commonly found in Florida. The strains produced a compatible reaction on tomato genotype Hawaii 7998 (H7998), were amylolytic and pectolytic, and were classified originally as T2 strains. However, these strains produced a rapid hypersensitive response when infiltrated into the tomato genotypes Hawaii 7981 (H7981), PI 126932, and PI 128216, whereas T2 strains produced a compatible reaction. In an experiment where electrolyte leakage was determined in leaflets of tomato cv. Bonny Best (compatible with all tomato strains), H7998 (resistant to T1 strains), and the two PIs, a member of these new strains induced a rapid hypersensitive response in the three tomato genotypes, whereas a T2 strain did not. After low concentrations of bacteria were infiltrated into the mesophyll of leaflets of PI 126932, PI 128216, H7998, and cv. Walter (compatible with all tomato strains), internal populations of the amylolytic, pectolytic Florida strain were reduced when tested in the first two genotypes but not in the latter two genotypes. Populations of the T1 strain were reduced only in H7998. These new strains are designated tomato race 3 (T3). When the T3 strains were compared with a representative group of T1 and T2 strains by fatty acid analysis and carbon substrate utilization patterns, the new T3 strains clustered distinctly from representative T1 and T2 strains. The evidence suggests the T3 strain is a recent introduction to Florida. An amylolytic, pectolytic strain isolated from seed grown in Thailand reacted similarly to the T3 strains on the tomato differentials. It also clustered with the T3 strains in the fatty acid and carbon substrate utilization dendrograms
84049437
Physiological, chemical, serological, and pathogenic analyses of a worldwide collection of Xanthomonas campestris pv. vesicatoria strains.
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 [...]