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1.
A newly discovered bacterial species, Pseudomonas floridensis, has emerged as a pathogen of tomato in Florida. This study compares the virulence and other attributes of P. floridensis to Pseudomonas syringae pv. tomato, which causes bacterial speck disease of tomato. Pseudomonas floridensis reached lower population levels in leaves of tomato as compared to the P. syringae pv. tomato strains DC3000 and NYT1. Analysis of the genome sequence of the P. floridensis type strain GEV388 revealed that it has just nine type III effectors including AvrPtoBGEV388, which is 66% identical to AvrPtoB in DC3000. Five of these effectors have been previously reported to be members of a ‘minimal effector repertoire’ required for full DC3000 virulence on Nicotiana benthamiana; however, GEV388 grew poorly on leaves of this plant species compared to the DC3000 minimal effector strain. The tomato Pto gene recognizes AvrPtoB in race 0 P. syringae pv. tomato strains, thereby conferring resistance to bacterial speck disease. Pto was also found to confer resistance to P. floridensis, indicating this gene will be useful in the protection of tomato against this newly emerged pathogen.  相似文献   

2.
Bacterial speck caused byPseudomonas syringae pv.tomato is an emerging disease of tomato in Tanzania. Following reports of outbreaks of the disease in many locations in Tanzania, 56 isolates ofP. syringae pv.tomato were collected from four tomato- producing areas and characterized using pathogenicity assays on tomato, carbon source utilization by the Biolog Microplate system, polymerase chain reaction and restriction fragment length polymorphism (RFLP) analysis. All theP. syringae pv.tomato isolates produced bacterial speck symptoms on susceptible tomato (cv. ‘Tanya’) seedlings. Metabolic fingerprinting profiles revealed diversity among the isolates, forming several clusters. Some geographic differentiation was observed in principal component analysis, with isolates from Arusha region being more diverse than those from Iringa and Morogoro regions. The Biolog system was efficient in the identification of the isolates to the species level, as 53 of the 56 (94.6%) isolates ofP. syringae pv.tomato were identified asPseudomonas syringae. However, only 23 isolates out of the 56 (41.1%) were identified asPseudomonas syringae pv.tomato. The results of this work indicate the existence ofP. syringae pv.tomato isolates in Tanzania that differ significantly from those used to create the Biolog database. RFLP analysis showed that the isolates were highly conserved in theirhrpZ gene. The low level of genomic diversity within the pathogen in Tanzania shows that there is a possibility to use resistant tomato varieties as part of an effective integrated bacterial speck management plan. http://www.phytoparasitica.org posting August 8, 2008.  相似文献   

3.
Bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, was observed to cause severe symptoms, especially on protected tomato crops, during the winter season in the coastal area of Lebanon. This study was conducted to investigate the aetiology and pathogenesis of the bacterium involved and the efficacy of different chemicals for the control of the disease. Biochemical, physiological and pathological tests verified the identity of the bacterium involved as P. s. tomato. Periodic histological sectioning of inoculated tomato leaves showed that bacterial cells resided and multiplied in depressions and around trichome bases for 24 h before penetration through stomata and trichome basal cells. The bacteria invaded intercellular spaces and caused cell lignification, collapse and shrinkage, 48 h after inoculation. Necrotic lesions filled with bacterial masses and collapsed lignified cells were readily observable at and after 72 h. No detectable histological changes were observed in the yellow halo region surrounding the necrotic leaf specks. A thermostable toxin was produced by the pathogen and is involved in chlorotic symptom expression. An antibiotic mixture of streptomycin + oxytetracy‐cline was most effective in controlling infections followed by copper oxychloride + mancozeb, tribasic copper sulphate + sulphur, copper oxychloride and copper oxychloride + zineb.  相似文献   

4.
A rapid detection method based on PCR amplification of Pseudomonas syringae pv. tomato chromosomal sequences was developed. Primer design was based on the P. syringae DC3000 hrpZPst gene, which maps on a pathogenicity-associated operon of the hrp/hrc pathogenicity island.A 532 bp product corresponding to an internal fragment of hrpZPst was amplified from 50 isolates of P. syringae pv. tomato belonging to a geographically representative collection. The amplification product was also obtained from three coronatine-deficient strains of P. syringae pv. tomato.On the other hand, PCR did not produce any such products from 100 pathogenic and symbiotic bacterial strains of the genera Pseudomonas, Xanthomonas, Erwinia, and Rhizobium and 75 unidentified bacterial saprophytes isolated from tomato plants. The method was tested using leaf and fruit spots from naturally-infected tomato plants and asymptomatic nursery plants and artificially contaminated tomato seeds. The results confirmed the high specificity observed using pure cultures.  相似文献   

5.
An early event correlated with the gene-for-gene hypersensitive response (HR) is the accumulation of active oxygen species (AOS), also known as the oxidative burst. We present data that genetically demonstrates that the oxidative burst is a downstream component of the RPS2- avrRpt2gene-for-gene signal cascade. An in planta AOS assay using the fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) was modified for use with the Arabidopsis thaliana / Pseudomonas syringae pv.tomato (P. syringae pv. tomato) model system. An oxidative burst occurred between 8 and 15 hpi with avirulent P. syringae pv. tomato(avrRpt2), but not with virulent P. syringae pv. tomato. This burst preceded cell death and was not observed in the RPS2 Arabidopsis mutantsrps2-101C and rps2-201 inoculated with avirulent P. syringae pv. tomato. An HR-like response has been observed when plants undergoing a systemic acquired resistance (SAR) response are challenged with a normally virulent pathogen (manifestation stage of SAR), however an HR-like oxidative burst was not detected by the in planta AOS assay during this stage of SAR.  相似文献   

6.
Pseudomonas syringae pv. tomato has been observed in the fields in Sinaloa causing typical symptoms of bacterial speck. During the 2004?C2005 growing seasons atypical symptoms were observed in tomato varieties grown in Sinaloa, consisting of external necrosis of stems, petioles, peduncles and fruit calyxes. Although the disease affected 80?C90% of the foliage, there were no speck symptoms on fruit. The objectives of this study were to: (a) identify the causal agent of the disease, (b) determine the sensitivity of the pathogen to various antibiotics in vitro and (c) test their efficacy for controlling the disease in tomato plants under greenhouse conditions. The results of the present study indicate that biochemical and physiological characteristics as well as the molecular studies of bacterial isolates associated with the yellow halo spot and external necrosis of the stem of tomato are closely related to P. syringae pv. tomato, although whether these isolates indeed belong to pathovar tomato needs further assessment. The efficacy of gentamicin sulfate and oxytetracycline chlorhydrate in vitro, and in planta under greenhouse conditions, represents a possible option for the chemical control of the disease under field conditions. The results also indicate a reduced sensitivity of the characterized isolates to copper hydroxide as compared with the above mentioned antibiotics in northern Sinaloa.  相似文献   

7.
Pseudomonas tomato, the causal agent of bacterial speck of tomato (Lycopersicon esculentum), was isolated on King B medium supplemented with penicillin and cycloheximide. An inoculum concentration of 104-105 colony-forming units per ml was used to obtain typical symptoms. Wounding of leaves by rubbing them with carborundum powder, or spraying with diluted wax solvent, significantly increased disease incidence. The best inoculation was obtained by subjecting the plants to 40°C for 30 min to 3 h or by incubating them for 24 h under mist prior to inoculation. The physiological age of the plants did not affect disease development. The bacteria survived in and were reisolated from soils, commercial seeds and plants after periods varying from 2 months to one year.  相似文献   

8.
Lycopersicon esculentum cultivar Micro-Tom is a miniature tomato with many advantages for studies of the molecular biology and physiology of plants. To evaluate the suitability of Micro-Tom as a host plant for the study of pathogenesis, Micro-Tom plants were inoculated with 16 well-known fungal, bacterial, and viral pathogens of tomato. Athelia rolfsii, Botryotinia fuckeliana, Oidium sp., Phytophthora infestans, and Sclerotinia sclerotiorum caused typical symptoms and sporulated abundantly on Micro-Tom. Micro-Tom was resistant to Alternaria alternata, Corynespora cassiicola, and Fusarium oxysporum. When Micro-Tom was inoculated with 17 isolates of Ralstonia solanacearum, many isolates induced wilt symptoms. Agrobacterium tumefaciens also was pathogenic, causing crown galls on stem tissue after needle prick inoculation. In Micro-Tom sprayed with Pseudomonas syringae pv. tomato, P. s. pv. tabaci, or P. s. pv. glycinea, bacterial populations did not increase, and yellow lesions appeared only on leaves sprayed with P. s. pv. tomato. Tomato mosaic virus, Tomato aspermy virus, and Cucumber mosaic virus systemically infected Micro-Tom, which developed symptoms characteristic of other cultivars of tomato after infection with the respective virus. These results indicated that Micro-Tom was generally susceptible to most of the important tomato pathogens and developed typical symptoms, whereas certain pathogens were restricted by either hypersensitive resistance or nonhost resistance on Micro-Tom. Therefore, an assortment of Micro-Tom–pathogen systems should provide excellent models for studying the mechanism of susceptible and resistant interactions between plants and pathogens.  相似文献   

9.
When lower leaves of rice plants were inoculated with powder formulation of a saprophytic strain ofPseudomonas fluorescens, Pfl, upper leaves, in addition to the inoculated lower leaves, showed resistance to the rice bacterial blight pathogenXanthomonas oryzae pv.oryzae. When the leaves were challenge-inoculated withX. oryzae pv.oryzae 4 days afterP. fluorescens application on lower leaves, the disease intensity in upper leaves decreased from 6.7 to 1.1. When rice seeds were treated with the formulation ofP. fluorescens Pfl and sown, 30-day-old seedlings showed resistance toX. oryzae pv.oryzae and the disease intensity decreased from 6.8 to 1.2. The induced resistance was transient; leaves sprayed withP. fluorescens Pfl at 30 days after treatment and leaves of 60-day-old seedlings fromP. fluorescens-treated seeds did not show resistance to the pathogen. In field trials, seed treatment followed by foliar application of the powder formulation ofP. fluorescens Pfl effectively controlled rice bacterial blight and increased the yield. In the induced resistant leaves a sharp increase in lignification and activities of peroxidase, phenylalanine ammonia-lyase and 4-coumarate: CoA ligase was observed when the leaves were challenge-inoculated withX. oryzae pv.oryzae. An approximately threefold increase in lignin content, peroxidase activity and phenylalanine ammonia-lyase activity and a fivefold increase in 4-coumarate: CoA ligase activity were observed 5 days after challenge inoculation withX. oryzae pv.oryzae in rice leaves pretreated withP. fluorescens for 5 days. A similar increase in defense-related activities was not observed in susceptible interactions or inP. fluorescens-treated plants at later stages of interactions when no resistance to the pathogen was observed.  相似文献   

10.
The development of a rapid detection method for Xanthomonas campestris pv. campestris (Xcc) in crucifer seeds and plants is essential for high-throughput certification purposes. Here we describe a diagnostic protocol for the identification/detection of Xcc by PCR amplification of fragments from the pathogenicity-associated gene hrcC. Under stringent conditions of amplification, a PCR product of 519 bp from hrcC was obtained from a collection of 46 isolates of Xcc, with the exception of two isolates from radish. No amplicons were obtained from 39 pure cultures of the phytopathogenic bacteria Xanthomonas campestris pv. cerealicola, X. campestris pv. juglandis, X. campestris pv. pelargonii, X. campestris pv. vitians, X. arboricola pv. pruni, X. axonopodis pv. phaseoli, X. axonopodis pv. vesicatoria, X. vesicatoria, Pseudomonas syringae pv. phaseolicola, P. syringae pv. syringae, P. syringae pv. tomato, P. fluorescens, P. marginalis, Pectobacterium atrosepticum, P. carotovorum subsp. carotovorum. In addition, PCR reactions were negative for fifty unidentified environmental isolates purified from the surface of crucifers. The PCR fragment was obtained from four strains previously classified as X. campestris pv. aberrans, X. campestris pv. armorociae, X. campestris pv. barbarae and X. campestris pv. incanae using pathogenicity assays. Our PCR protocol specifically detected Xcc in inoculated leaves, seeds and naturally infected leaves of crucifers.  相似文献   

11.
A new bacterial black spot disease was observed on Odontoglossum, Odontioda, Odontocidium, and Vuylstekeara orchids in Japan. Typical symptoms on the leaves were dark or black spots (or both) with a yellow halo. The causal agent was identified as Burkholderia andropogonis (Smith 1911) Gillis, Van Van, Bardin, Goor, Hebbar, Willems, Segers, Kersters, Heulin and Fernandez 1995. The isolates were pathogenic on four original host orchids, Phalaenopsis orchid, and tulip; they were not pathogenic on white clover or corn after needle stab inoculation. An antibiotic bactericide (oxytetracycline/streptomycin mixture WP) was most effective for controlling the disease.  相似文献   

12.
Flagellin, an essential component of the bacterial flagellar filament, is capable of inducing a hypersensitive response (HR), including cell death, in a nonhost plant. A flagellin-defective mutant (ΔfliC) of Pseudomonas syringae pv. tabaci lacks both the flagellar filament and motility, whereas a flagellin-glycosylation-defective mutant (Δorf1) retains the flagellar filament but lacks the glycosyl modification of flagellin protein. To investigate the role of flagellin protein and its glycosylation in the interaction with its nonhost Arabidopsis thaliana, we analyzed plant responses after inoculation with these bacteria. Inoculation with wild-type P. syringae pv. tabaci induced HR, with the generation of reactive oxygen species and cell death. In contrast, inoculation with either ΔfliC or Δorf1 mutant induced a low level of HR, and inoculated leaves developed a disease-like yellowing. These mutant bacteria multiplied better than the wild-type bacteria in A. thaliana. These results indicate that A. thaliana expresses a defense reaction in response to the bacterial flagellin with its glycosyl structure.  相似文献   

13.
A bacterial strain, CFBP 3388, isolated from Vetch (Vicia sativa, L.) was identified asP. s. pv.syringae on the basis of nutritional and biochemical patterns which were obtained with classical tests and the Biolog system. It caused necrotic symptoms typical ofP. s. pv.syringae on bean leaves and pods after artificial inoculation. However, the isolate caused a citrulline-reversible inhibition ofE. coli in phaseolotoxin bioassay. Furthermore, with CFBP 3388 DNA as template a 1900 bp DNA fragment, specific for the phaseolotoxin DNA cluster ofP. s. pv.phaseolicola, was amplified by PCR. This is the first demonstration that an isolate ofP. syringae that is not pv.phaseolicola can produce phaseolotoxinAbbreviations bp base pair - kb kilobase - OCT Ornithine Carbamoyl Transferase  相似文献   

14.
A scheme for routine seed testing forXanthomonas campestris pv.vesicatoria andPseudomonas syringae pv.tomato in pepper and tomato seeds was developed. The scheme is based on different bacterial enrichment techniques. As few as 1000 and 10–100 colony forming units per gram of seeds were detected using a liquid enrichment technique or leaf enrichment technique, respectively. Relatively large amounts of saprophytes on the seed surfaces did not interfere with the detection of the pathogens.  相似文献   

15.
Bacterial canker is one of the most important diseases of cherry (Prunus avium). This disease can be caused by two pathovars of Pseudomonas syringae: pv. morsprunorum and pv. syringae. Repetitive DNA polymerase chain reaction-based fingerprinting (rep-PCR) was investigated as a method to distinguish pathovars, races and isolates of P. syringae from sweet and wild cherry. After amplification of total genomic DNA from 87 isolates using the REP (repetitive extragenic palindromic), ERIC (enterobacterial repetitive intergenic consensus) and BOX primers, followed by agarose gel electrophoresis, groups of isolates showed specific patterns of PCR products. Pseudomonas syringae pv. syringae isolates were highly variable. The differences amongst the fingerprints of P. syringae pv. morsprunorum race 1 isolates were small. The patterns of P. syringae pv. morsprunorum race 2 isolates were also very uniform, with one exception, and distinct from the race 1 isolates. rep-PCR is a rapid and simple method to identify isolates of the two races of P. syringae pv. morsprunorum; this method can also assist in the identification of P. syringae pv. syringae isolates, although it cannot replace inoculation on susceptible hosts such as cherry and lilac.  相似文献   

16.
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17.
Bacterial blight of cantaloupe (Cucumis melo) caused by Pseudomonas syringae pv. aptata was first observed in south-western France and has since spread to all cantaloupe-growing areas of this country. Use of pesticides registered for this disease has proved ineffective and no commercial cultivars of cantaloupe are resistant to this blight. To develop control strategies for this disease, the principal sources of inoculum were investigated. Among the different sources of inoculum studied, we report the isolation of P. syringae pv. aptata from irrigation water retention basins in south-western France using the immunofluorescence colony-staining (IFC) method. In this study, the pathogen was detected at a low concentration (12 and 70cful–1) in two different retention basins. These results suggest that P. syringae pv. aptata can survive in water used to irrigate cantaloupe crops and could be a source of inoculum for epidemics of bacterial blight. To develop control strategies for this bacterial disease, the importance of water retention basins as sources of inoculum for bacterial blight of cantaloupe needs to be evaluated relative to other potential sources such as seeds, plants from nurseries and plant debris in the soil.  相似文献   

18.
The flagellins purified from Pseudomonas syringae pv. tabaci induce a hypersensitive reaction in nonhost tomato cells. To investigate the role of flagella and flagellin in the compatible interaction, we generated two types of flagella-defective mutant. The fliC mutant lost the fliC gene that encodes flagellin protein, whereas the fliD mutant lost the fliD gene that encodes HAP2-capping protein. The two mutants had markedly reduced ability to cause disease symptoms in tobacco leaves. Furthermore, propagation of the mutants in tobacco leaves was less than that in wild-type pv. tabaci. Compared to the inoculation with wild-type pv. tabaci, inoculation with the two mutants did not markedly induce the expression of typical defense response-related genes such as PAL and hsr203J. Complementation of each fliC and fliD gene to the corresponding deficient mutant restored motility and virulence. These results indicate that flagella of P. syringae pv. tabaci are indispensable organelles for complete virulence on host tobacco plants.  相似文献   

19.
Coronatine (COR) functions as a virulence factor in the interaction of Pseudomonas syringae pv. tomato strain DC3000 with tomato and Arabidopsis. COR consists of two moieties, coronafacic acid (CFA) and coronamic acid (CMA). Both COR and CFA function as structural and functional analogues of jasmonic acid (JA) and related signaling compounds such as methyl jasmonate (MeJA) and JA-isoleucine (JA-Ile). The precise function of COR and whether MeJA functions as an analogue of COR in disease development are not known. In this study, we analyzed whether the COR-defective mutant DB29, which is a CFA− CMA− mutant of DC3000, could be complemented for virulence via the exogenous application of COR, CFA, or MeJA. When tomato seedlings were inoculated with DB29 and supplemented with exogenous COR, the DB29 population multiplied in tomato seedlings and induced disease phenotypes similar to wild-type DC3000. Although the addition of exogenous MeJA or CFA enhanced the multiplication of DB29, wild-type disease phenotypes could not be restored with these compounds. Furthermore, inoculation of DB29 along with exogenous COR, but not MeJA or CFA, suppressed the expression of defense-related genes and increased the accumulation of reactive oxygen species, which are associated with severe chlorosis. Taken together, our results suggest that although COR targets the jasmonate pathway by mimicking JA, the function of COR in disease development is distinctly different from MeJA or CFA.  相似文献   

20.
We have previously shown that flagellin of Pseudomonas syringae pv. tabaci is an elicitor that induces a hypersensitive reaction (HR) in nonhost tomato cells. Flagellin is the major HR elicitor produced by this pathogen, as shown by the inability of a flagellin-defective mutant, ΔfliC, to induce HR. Also, a ΔfliD mutant that secretes large amounts of monomer flagellins induces a strong HR in tomato. In this study, the possible involvement of an Hrp type III secretion system (TTSS) in flagellin-induced HR was investigated using flagella-defective mutants or Hrp TTSS-defective mutants. The hrcC gene encodes HrcC protein, which is required for Hrp pilus formation in the outer membrane. An hrcC mutation, introduced into the wild-type, ΔfliC, and ΔfliD mutants of P. syringae pv. tabaci did not affect swimming motility or flagellin secretion, whereas all ΔhrcC, ΔfliC, and ΔfliD mutants lost the ability to cause disease on host tobacco leaves. However, the ΔhrcC mutant and the ΔfliD/ΔhrcC double mutant were still able to induce HR cell death, expression of one of the defense-related genes hsr203J, and the generation of hydrogen peroxide in nonhost tomato cells. Thus, flagellin is required for both pathogenicity in host tobacco and HR in nonhost tomato. On the other hand, hrp TTSS is necessary for pathogenicity on host tobacco but is not indispensable to induce HR in nonhost tomato. These results clearly show that flagellin-induced HR is hrp-independent in tomato.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB049570  相似文献   

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