Academic literature on the topic 'Xanthomonas translucens'

In order to confirm and refine the current classification scheme of Xanthomonas translucens and to identify novel strains from ornamental asparagus, a collection of field and reference strains was analyzed. Rep-polymerase chain reaction (PCR) genomic fingerprint profiles were generated from 33 isolates pathogenic to asparagus as well as 61 X. trans-lucens reference strains pathogenic to cereals and grasses. Amplified ribo-somal gene restriction analysis profiles were obtained from most of these and 29 additional Xanthomonas reference strains. Rep-PCR genomic fingerprint profiles of all strains were compared with those in a large Xanthomonas database using computer-assisted analysis. Rep-PCR ge-nomic fingerprinting facilitated the characterization and discrimination of X. translucens, including the pathovars arrhenatheri, graminis, phlei, phleipratensis, and poae, as well as a number of strains received as X. translucens pv. cerealis. Strains received as pathovars hordei, secalis, translucens, undulosa, and other cerealis strains were grouped in two subclusters that correspond to the recently redefined pathovars X. trans-lucens pvs. undulosa and translucens. All 33 novel isolates from ornamental asparagus (tree fern; Asparagus virgatus) were identified as X. translucens pv. undulosa. Moreover, a unique amplified small subunit ribosomal gene MspI/AluI restriction profile specific for all X. translucens strains tested, including those pathogenic to asparagus, allowed discrimination from all other Xanthomonas spp. Although phage tests were inconclusive, the classification of the asparagus strains within the X. translucens complex was supported by pathogenicity assays in which all the isolates from ornamental asparagus induced watersoaking on wheat. Surprisingly, several X. translucens reference strains affected asparagus tree fern as well. That the novel asparagus isolates belong to X. translucens pv. undulosa is extraordinary because all hosts of X. translucens pathovars described to date belong only to the families Gramineae and Poaceae, whereas asparagus belongs to the phylogenetically distant family Liliaceae.

Sixty-eight presumptive Xanthomonas translucens strains isolated from 15 small grains or grass species were studied by pathogenicity tests on barley, bread wheat, oat, and bromegrass species, and also by AFLP, analysis of fatty acid methyl esters (FAME), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of protein extracts. The X. translucens strains were divided into three pathogenicity types based on differences observed on barley and bread wheat. Two unspeciated strains producing atypical symptoms formed a fourth pathogenicity type. Pathogenicity on oat and bromegrass species varied within these types. Clusterings observed by AFLP analysis and, to a lesser extent, by FAME analysis were consistent with these pathogenicity groupings. The current results, as well as those of previous restriction fragment length polymorphism analyses of the same strains, support the recent reclassification of X. translucens pv. translucens and X. translucens pv. hordei as true synonyms. X. translucens pv. cerealis, X. translucens pv. translucens, and X. translucens pv. undulosa cluster in different groups by AFLP and FAME analyses. Even though distinction by simple biochemical tests is not clear-cut, the data indicate that the pathovars cerealis, translucens, and undulosa correspond to true biological entities.

Xanthomonas translucens pv. translucens causes bacterial leaf streak and bacterial blight diseases of barley. This pathogen limits barley production globally but remains understudied, with limited genomic resources. To better understand the biology of this X. translucens subgroup, we sequenced the complete genome of the X. translucens pv. translucens strain UPB886.

Bacterial leaf streak caused by different pathovars of Xanthomonas translucens is the most important seedborne bacterial disease of small grain cereals. However, variations in the virulence-associated genomic areas of the pathogen remain uninvestigated. In this study, the diversity of transcription activator-like effectors (TALE) was investigated using the Southern blotting of BamHI-digested genomic DNAs in the Iranian strains of X. translucens. All 65 X. translucens strains were assigned into 13 genotypes, where 57 X. translucens pv. undulosa strains were placed in genotypes 1 to 8, and seven X. translucens pv. translucens strains were placed in genotypes 9 to 12. Interestingly, we did not find any TALE genes in the strain XtKm7 (genotype 13), which showed to be pathogenic only on barley. Virulence and aggressiveness of these strains in greenhouse conditions were in agreement with the TALE-based clustering of the strains in the pathovar level, though variations were observed in the aggressiveness of X. translucens pv. undulosa strains. In general, strains containing higher numbers of putative TALE genes were more virulent on wheat and barley than strains containing fewer. This is the first TALE-based genetic diversity analysis on X. translucens strains and provides novel insights into the virulence repertories and genomic characteristics of the pathogen. Further investigations using TALE mutagenesis and complementation analysis are warranted to precisely elucidate the role of each detected X. translucens TALE in bacterial virulence and aggressiveness either on wheat or barley.

The relationship between leaf-associated population sizes of Xanthomonas translucens pv. translucens on asymptomatic leaves and subsequent bacterial leaf streak (BLS) severity was investigated. In three experiments, X. translucens pv. translucens was spray-inoculated onto 10-day-old wheat seedlings over a range of inoculum densities (104, 105, 106, 107, and 108 CFU/ml). Lesions developed most rapidly on plants inoculated with higher densities of X. translucens pv. translucens. Leaf-associated pathogen population sizes recovered 48 h after inoculation were highly predictive of BLS severity 7 days after inoculation (R2 = 0.970, P < 0.0001). The relationship between pathogen population size on leaves and subsequent BLS severity was best described by the logistic model. Leaf-associated X. translucens pv. translucens population size and BLS severity from a particular pathogen inoculum density often varied among experiments; however, the disease severity level caused by a particular leaf-associated X. translucens pv. translucens population size was not significantly different among experiments. Biological and disease control implications of the X. translucens pv. translucens population size-BLS severity relationship are discussed.

Bacterial leaf streak (BLS) of wheat and barley, caused by Xanthomonas translucens pv. undulosa and X. translucens pv. translucens, has been of growing concern in small grains production in the Upper Midwestern United States. To optimize disease resistance breeding, a greater awareness is needed of the pathovars and genetic diversity within the pathogens causing BLS in the region. Multilocus sequencing typing (MLST) and analysis (MLSA) of four common housekeeping genes (rpoD, dnaK, fyuA, and gyrB) was used to evaluate the genetic diversity of 82 strains of X. translucens isolated between 2006 and 2013 from wheat, barley, rye, and intermediate wheatgrass. In addition, in planta disease assays were conducted on 75 strains to measure relative virulence in wheat and barley. All strains were determined by MLSA to be related to X. translucens pv. undulosa and X. translucens pv. translucens. Clustering of strains based on Bayesian, network, and minimum spanning trees correlated with relative virulence levels in inoculated wheat and barley. Thus, phylogeny based on rpoD, dnaK, fyuA, and gyrB correlated with host of isolation and was an effective means for predicting virulence of strains belonging to X. translucens pv. translucens and X. translucens pv. undulosa.

Rice straw can be utilized as an organic substrate in Microbial Fuel Cell (MFC) to generate electricity by microbes as a biocatalyst. This research was aimed to observe the effect of Xanthomonas translucens ICBB 9762 inoculation pretreatment on microwave-assisted alkali treated rice straw on the lignocellulosic structure change of rice straw and to observe the performance of MFC system fed by treated rice straw. The stages of research included: (1) pretreatment of rice straw through microwave-assisted alkali and Xanthomonas translucens ICBB 9762 inoculation, (2) observation of MFC performance including electrical voltage; electrical current; power density; and Coulombic efficiency, and (3) anolite analysis including COD removal, pH and Eh. The result showed that rice straw was successfully decomposed by inoculation of Xanthomonas translucens ICBB 9762 on microwave-assisted alkali pretreatment which the highest cellulose yield about 29.36 %. Treated rice straw produced better performance than rice straw without pretreatment which the best performance resulted by the combination of Xanthomonas translucens ICBB 9762 inoculation and microwave-assisted alkali pretreatment which produce electrical voltage, electrical current, and power density value of 337.90 mV, 0.39 mA, and 26.20 mW/m2, respectively. The utilization of solid substrate such as rice straw need more attention due to there was COD enhancement while in COD reduction reach COD removal efficiency and coulombic efficiency ranged 5.15 - 54.08 % and 0.25 - 7.83 %, respectively. HIGHLIGHTS Microbial Fuel Cell fueled by lignocellulose substrate, which is rice straw Lignocellulose structure deconstruction through microwave-assisted alkali pretreatment A combination of microwave-assisted alkali and cellulose-degrading bacteria inoculation pretreatment for rice straw generate the highest electricity Electricity generation improvement in microbial fuel cell through mix culture between cellulose-degrading bacteria and exoelectrogen bacteria Cellulose degrading bacteria increase Chemical Oxygen Demand (COD) due to the solubility of low molecular weight organic compounds increasing during microbial fuel cell incubation

The genus of Xanthomonas contains many well-known plant pathogens with the ability to infect some of the most important crop plants, thereby causing significant economic damage. Unfortunately, classical pest-control strategies are neither particularly efficient nor sustainable and we are, therefore, in demand of alternatives. Here, we present the isolation and characterization of seven novel phages infecting the plant-pathogenic species Xanthomonas translucens and Xanthomonas campestris. Transmission electron microscopy revealed that all phages show a siphovirion morphology. The analysis of genome sequences and plaque morphologies are in agreement with a lytic lifestyle of the phages making them suitable candidates for biocontrol. Moreover, three of the isolated phages form the new genus “Shirevirus”. All seven phages belong to four distinct clusters underpinning their phylogenetic diversity. Altogether, this study presents the first characterized isolates for the plant pathogen X. translucens and expands the number of available phages for plant biocontrol.

The relationship between foliar disease symptoms on parent plants, seed contamination by the causal bacterium (Xanthomonas translucens pv. translucens), and subsequent development of bacterial leaf streak in wheat was studied in microplots and in the laboratory to determine the role of seed transmission in disease epidemiology. Microplot experiments were carried out during the 1994-95 and 1995-96 growing seasons using seed harvested in Baton Rouge, Louisiana, in 1994 and 1995, respectively. Treatments were seed lots from plants with differing levels of bacterial leaf streak severity on the flag leaves of the parent tillers. X. translucens pv. translucens was detected in 1 to 20% of seed from susceptible cultivars Florida 304 and Savannah collected from plants with leaf streak symptoms. Correlations between seed contamination and disease on plants that developed from this seed were detected only when seed came from parent tillers that expressed flag leaf disease severity ≥15 to 20% in 1994-95 and ≥30 to 35% in 1995-96. However, symptoms of bacterial leaf streak on plants that developed from these seed were evident on only ≤3% of plants. Results suggest a possible threshold level for bacterial leaf streak on flag leaves that is necessary before X. translucens pv. translucens can be detected in seed. Seedling emergence in microplots correlated negatively with leaf streak severity on parent tiller flag leaves. Artificial infestation of seed with X. translucens pv. translucens also reduced seed germination, but this was more evident in Savannah than in Florida 304.

Prevalence of Xanthomonas translucens, which causes cereal leaf streak (CLS) in cereal crops and bacterial wilt in forage and turfgrass species, has increased in many regions in recent years. Because the pathogen is seedborne in economically important cereals, it is a concern for international and interstate germplasm exchange and, thus, reliable and robust protocols for its detection in seed are needed. However, historical confusion surrounding the taxonomy within the species has complicated the development of accurate and reliable diagnostic tools for X. translucens. Therefore, we sequenced genomes of 15 X. translucens strains representing six different pathovars and compared them with additional publicly available X. translucens genome sequences to obtain a genome-based phylogeny for robust classification of this species. Our results reveal three main clusters: one consisting of pv. cerealis, one consisting of pvs. undulosa and translucens, and a third consisting of pvs. arrhenatheri, graminis, phlei, and poae. Based on genomic differences, diagnostic loop-mediated isothermal amplification (LAMP) primers were developed that clearly distinguish strains that cause disease on cereals, such as pvs. undulosa, translucens, hordei, and secalis, from strains that cause disease on noncereal hosts, such as pvs. arrhenatheri, cerealis, graminis, phlei, and poae. Additional LAMP assays were developed that selectively amplify strains belonging to pvs. cerealis and poae, distinguishing them from other pathovars. These primers will be instrumental in diagnostics when implementing quarantine regulations to limit further geographic spread of X. translucens pathovars.

Bacterial blight of barley, caused by the bacterium Xanthomonas translucens, occurs sporadically in Arizona in sprinkler-irrigated barley. The pathogen is seed borne, and there are no resistant varieties of barley. Bacterial blight has been severe when contaminated seed is planted and favorable weather conditions, including spring rains and late frosts, occur in March and April. Methods for detection of the bacteria on seed have been established at The University of Arizona using both standard pathogenicity trials on barley seedlings and immunoassay techniques.

Xanthomonas translucens (Xtp) causes dieback disease of pistachio in Australia. The bacterium infects the vascular tissues of the trees, causing discolouration of the xylem, lesions on the trunk and major limbs, decline and, in some cases, death. Although hygiene and application of quaternary ammonium disinfectant to pruning wounds have been recommended to limit the spread of the disease, effective control methods are lacking. Biological control offers potential in managing this disease. The aims of this research were to assess the ability of selected bacteria to antagonise Xtp and to evaluate the ability of the synthetic peptide BP100 to suppress growth of Xtp in liquid medium. Isolate KI of X. translucens (DAR75532), obtained from a commercial pistachio orchard in Kyalite (NSW) was used. The potential antagonists comprised one isolate of Bacillus subtilis and several bacteria isolated from pistachio wood and stored following indications of ability to inhibit Xtp. Preliminary screening of the potential antagonists was conducted by means of an agar diffusion assay, in sucrose peptone agar (SPA) and nutrient agar (NA). Inhibition of growth of DAR75532 varied among bacterial isolates and with the culture medium used. Generally, the isolates produced larger inhibition zones on SPA than on NA and appeared to be bacteriostatic. When diffusible compounds were extracted from liquid cultures through centrifugation and filtration, there was no evidence of antibiotic activity. Further experiments demonstrated that two antagonists produced antibacterial metabolites in liquid medium. In contrast, culture filtrate of isolate 64161-7 grown in nutrient broth supplemented with yeast extract and glucose inhibited DAR75532, and filtrate from isolate PC397 grown in the same medium, or in nutrient broth supplemented with yeast extract and nutrient broth alone, was inhibitory. However, the antibiotic effect of PC397 was lost as the cell free culture filtrate was diluted. Competition was also identified as a possible mechanism, as DAR75532 was not recovered on SPA when mixed with isolates 64161-17, SUPP, B. subtilis, PC397, PC506 or PC507. An in vitro assay was developed to evaluate the ability of the potential antagonists to reduce colonisation of pistachio wood by DAR75532. The pathogen, antagonists 64161L and PC397, or pathogen plus antagonists were vacuum-infiltrated into non-autoclaved excised pistachio twigs, before incubating for 10 days. The pathogen and antagonists were recovered from the middle section of the wood, following soaking in saline and plating suspensions on SPA and NA supplemented with cephalexin, ampicillin and gentomicin (NA+ab). The antagonists were recovered and grew well on SPA but not NA+ab, indicating that they survived in pistachio wood. The pathogen was recovered on NA+ab and SPA, although indigenous wood-inhibiting bacteria also grew on SPA. Only PC397 was recovered from twigs inoculated with PC397 plus DAR75532. This suggested that PC397 inhibited colonisation of pistachio wood by the pathogen. Peptide BP100 was obtained from the University of Girona, Spain. A turbidimetric-based system was first used to monitor the effect of BP100 on growth of DAR75532 over time. Multiplication of DAR75532 in sucrose peptone broth (SPB) was delayed or reduced in the presence of BP100. At low concentration, the peptide was bacteriostatic and DAR75532 colonies were subsequently recovered on SPA. Higher concentrations were bactericidal. To verify bactericidal activity, suspensions of DAR75532 treated with peptide were sampled over time and the colony forming units enumerated on SPA and compared with untreated controls. The minimum inhibitory (bacteriostatic) or bactericidal concentration of BP100 was influenced by the initial concentration of DAR75532 and by incubation time. Peptide at 2.5 μM was sufficient to inhibit growth of DAR75532 in SPB when the initial concentration was 10⁶ CFU/ml, but a minimum of 5 μM was required to kill the cells. The mortality of DAR75532 three hours after treatment was 77.35% when 5 μM of peptide BP100 was applied. Preliminary screening had identified isolate 64161-7 as having potential to inhibit DAR75532. The isolate was tentatively identified as Pseudomonas tolaasii, P. fluorescens or P. putida by the National Collection of Plant Pathogenic Bacteria (UK). Although this isolate survived well in excised twigs of pistachio, it did not prevent colonisation of the wood by DAR75532. However, PC397, likely to be a Bacillus sp., reduced colonisation by DAR75532. The other six potential antagonists remain to be tested on pistachio wood. The effect of medium composition, such as sugar content, on antibiotic production should also be investigated. In addition, peptide BP100 offers promise as a means of controlling pistachio dieback. The ability of the bacterial isolates and the peptide to reduce colonisation of DAR75532 in pistachio trees should be assessed in a natural system where the influence of other factors can be evaluated.
Thesis (M.Ag.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010.

Bacterial pathogens are significant biotic factors of wheat, a globally important source of carbohydrates. The diseases caused by these pathogens are reported to reduce annual wheat production by about 10% and up to 40% in severe infections occurring early in the growth period. This chapter presents current information on the symptoms, distribution, identification, and taxonomy of key bacterial pathogens of wheat with a focus on the seed-borne bacterium, Xanthomonas translucens pv. undulosa, the causative agent of the leaf streak and black chaff disease. Other wheat-pathogenic bacterial pathogens addressed in the chapter are Pseudomonas syringae pv. syringae, the causal agent of bacterial leaf blight; P. syringae pv. atrofaciens that cause the basal glume rot; Pseudomonas fuscovaginae, the causal agent of the bacterial brown sheath; Erwinia rhapontici, the causal agent of the pink seed of wheat; Pseudomonas cichorii, the causative agent of wheat stem melanosis; Clavibacter tessellarius is responsible for the bacterial mosaic of wheat as well as other minor bacterial pathogens. Finally, the chapter proposed the use of genome-based tools for the accurate identification and classification of bacterial pathogens of wheat.