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1.
Pinellia ternata is a traditional Chinese herb which has been used in China for over 1,000 years. A soft-rot disease characterized by water-soaked lesions and soft-rot symptoms with a stinking odour was commonly observed in cultivated fields of this plant, and Pectobacterium-like bacteria were consistently isolated from the infected tissues. Two typical strains (SXR1 and ZJR1), isolated from Shanxi and Zhejiang, respectively, were identified. Pathogenicity tests revealed that these strains were virulent to P. ternata and induced the same symptoms as observed in the field. Characterization involving fatty acid profile, metabolic and physiological properties, 16S rDNA sequence and PCR-RFLP identified both isolates as P. carotovorum subsp. carotovorum (Pcc). The 16S rDNA of both isolates shared 97–99% sequence similarity with that of Pcc strains. The phylogenetic trees showed that both isolates were clustered in the group of Pcc and P. carotovorum subsp. odorifera and both PCR-RFLP profiles were consistent with the pattern E produced by the minority of Pcc strains. Thus, isolates SXR1 and ZJR1 were characterized as Pcc in spite of some differences. This is the first report that Pcc has been proven as a causal agent of soft-rot disease on P. ternata.  相似文献   

2.
Dickeya dadantii (syn. Erwinia chrysanthemi) is a causal agent of soft-rot diseases on many crops. Here, we characterized a gene belonging to the major facilitator superfamily (MFS), which is involved in the symport, antiport, or uniport of various substrates, and the survival and virulence of many Gram-negative bacterial animal pathogens, for the possible involvement in the plant pathogenicity of D. dadantii. A marker-exchange mutant of this gene (mfsX) was constructed that had decreased maceration ability in Chinese cabbage, potato, and chicory. Observation with electron microscopy showed greatly reduced numbers of flagella per cell. This mutant had a significant reduction in swimming and swarming motility and a severe reduction in formation of biofilm. Because these phenotypes have been shown to be involved in plant pathogenicity of D. dadantii, mfsX seems to play an important role in pathogenesis of D. dadantii 3937 by its involvement in the expression of these pathogenicity-related phenotypes.  相似文献   

3.
Vascular plants have various inducible resistance mechanisms as defense against pathogens. Mosses, small nonvascular plants (subkingdom Bryophyta), have been little studied in regard to their pathogens or modes of defense. Data here show that Erwinia carotovora, a bacterial plant pathogen that causes softrot in many dicotyledonous plants, can also cause soft rot symptoms in the moss Physcomitrella patens. Infection of moss by E. carotovora required pathogenicity factors similar to those required to infect vascular plants and, again as in vascular plants, salicylic acid (SA) induced moss to inhibit tissue maceration by Erwinia. These data reveal that SA-dependent defense pathways may have evolved before differentiation of vascular and nonvascular plants.  相似文献   

4.
The phylogenetic relationships among Erwinia amylovora biovar 4 (the pathogen of bacterial shoot blight of pear in Japan), other biovars of E. amylovora, and Erwinia pyrifoliae were investigated using the sequences of 16S rRNA, gyrB, and rpoD genes. The tested isolates formed two distinct monophyletic groups in the phylogenetic trees constructed based on the gyrB gene, rpoD gene, or a combination of the three genes: group 1 contained E. amylovora biovars 1, 2, and 3; group 2 contained E. amylovora bv. 4 and E. pyrifoliae. This phylogenetic analysis showed that E. amylovora bv. 4 was more closely related to E. pyrifoliae than to other biovars of E. amylovora. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB242876 to AB242925.  相似文献   

5.
Phialophora gregata f. sp. adzukicola, a causal agent of brown stem rot in adzuki beans, produces phytotoxic compounds: gregatins A, B, C, D, and E. Gregatins A, C, and D cause wilting and vascular browning in adzuki beans, which resemble the disease symptoms. Thus, gregatins are considered to be involved in pathogenicity. However, molecular analyses have not been conducted, and little is known about other pathogenic factors. We sought to isolate nonpathogenic and gregatin-deficient mutants through Agrobacterium tumefaciens-mediated transformation (ATMT) for cloning of pathogenicity-related genes. The co-cultivation of P. gregata and A. tumefaciens for 48 h at 20°C with 200 μM acetosyringone resulted in approximately 80 transformants per 106 conidia. The presence of acetosyringone in the A. tumefaciens pre-cultivation period led to an increase in T-DNA copy number per genome. Of 420 and 110 transformants tested for their pathogenicity and productivity of gregatins, one nonpathogenic and three gregatin-deficient mutants were obtained, respectively. The nonpathogenic mutant produced gregatins, whereas the gregatin-deficient mutants had pathogenicity comparable to the wild-type strain. This is the first report of ATMT of P. gregata. Further analysis of these mutants will help reveal the nature of the pathogenicity of this fungus including the role of gregatin in pathogenesis.  相似文献   

6.
Erwinia soft-rot is an important disease of many ornamental potted crops and is one of the most limiting factors in greenhouse calla lily (Zantedeschia spp.) production. Experiments were conducted to test the effect of phosphorous added to soil-less mixes or to nutrient solutions used for irrigation on soft-rot caused by Erwinia carotovora subsp. carotovora (Ecc). Soft-rot incidence increased to 51% when soil-less mix was amended with superphosphate in comparison to regular soil-less mix (no superphosphate added) (31%). In contrast, addition of phosphorous in the nutrient solution met the phosphorous needs of the plant without enhancing soft-rot. Plant height, fresh mass, and number of flowers per plant were greater in calla lilies irrigated with nutrient solution containing phosphorous than no phosphorous treatments. Similar results were obtained in tests conducted in a commercial greenhouse with larger sample size. No statistical differences were found between tubers sprayed with water (control) or with a 0.5 mM solution of KH2PO4 in laboratory experiments to determine the effect of phosphorous on tuber root development. In other experiments, tubers were sprayed with either water, a bacterial cell suspension 1 × 102 cfu ml–1, a solution of 0.5 mM KH2PO4, or a suspension of bacteria in KH2PO4. The results from these tests showed a significant increase of soft-rot development in tubers treated with the suspension of Ecc prepared in a solution of KH2PO4 relative to other treatments. Further laboratory tests indicated that enzymatic activity (polygalacturonase and pectate lyase) of Ecc increased when grown in the presence of phosphorous. These experiments suggest that increased soft-rot in the presence of phosphorous is due to increased virulence of Ecc.  相似文献   

7.
An oligonucleotide probe targeting the rRNA of Erwinia herbicola and Erwinia ananas was designed to detect their cells using fluorescence in situ hybridization. The Cy3-labeled probe hybridized strongly with these species but very weakly with nontarget species such as Erwinia mallotivora, Erwinia nigrifluens, Erwinia cypripedii, Erwinia chrysanthemi, Erwinia carotovora subsp. carotovora, E. carotovora subsp. atroseptica, and Escherichia coli. This technique visualized E. herbicola cells after inoculation of kumquat fruits. The probe is promising as a tool for studying population dynamics of E. herbicola and E. ananas.  相似文献   

8.
Isolates of an unidentified Rhizoctonia sp. (UR isolates) were obtained from creeping bentgrass and Kentucky bluegrass with reddish brown sheath and foliar rots. Because the UR isolates anastomosed with isolates of three varieties of Waitea circinata (var. oryzae, var. zeae, and var. circinata), colony morphology, hyphal growth rate at different temperatures, pathogenicity, sequence analysis of the internal transcribed spacers (ITS) region of ribosomal RNA genes (rDNA) were compared. The colony color of mature UR isolates was distinct from isolates of the other three varieties of W. circinata. In pathogenicity tests on creeping bentgrass, the severity of the disease caused by UR isolates was significantly higher than that caused by the three varieties of W. circinata. Sequence similarities of the rDNA-ITS region between UR isolates and between isolates within each variety were high (97–100%), but they were lower among isolates from UR and the varieties of W. circinata (88–94%). In a phylogenetic tree based on the rDNA-ITS sequences, UR isolates formed a cluster separate from each of the clusters formed by the three varieties of W. circinata. These results indicate that the UR isolates clearly differ from the three varieties of W. circinata. We therefore propose that the UR isolates be classified as new Rhizoctonia sp. that are closely related to W. circinata and that the disease on creeping bentgrass should be called Waitea reddish-brown patch disease (Sekikasshoku-hagusare-byo in Japanese).  相似文献   

9.
We selected a reduced-pathogenicity mutant of Fusarium oxysporum f. sp. lycopersici, a tomato wilt pathogen, from the transformants generated by restriction enzyme-mediated integration (REMI) transformation. The gene tagged with the plasmid in the mutant was predicted to encode a protein of 321 amino acids and was designated FPD1. Homology search showed its partial similarity to a chloride conductance regulatory protein of Xenopus, suggesting that FPD1 is a transmembrane protein. Although the function of FPD1 has not been identified, it does participate in the pathogenicity of F. oxysporum f. sp. lycopersici because FPD1-deficient mutants reproduced the reduced pathogenicity on tomato.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB110097  相似文献   

10.
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11.
A total of 88 strains of Erwinia carotovora subsp. carotovora (Ecc) isolated from various host plants in several geographic regions were screened for production of antibacterial substances using the same strains as indicators. Of the 88 strains, 72 produced antibacterial substances. One of these 72 strains, a Brazilian strain Ecc 32, produced an antibacterial substance active against all tested Ecc strains on TSA medium. The antibacterial spectrum of the compound from Ecc 32 strain was limited to closely related strains of soft-rot Erwinia species. Such a narrow spectrum of activity is typical of bacteriocins. The compound produced by Ecc 32 strain, however, was resistant to some enzymes and detergents. Moreover, the compound was heat-stable and active over a wide pH range. The physical characteristics of the compound were not in agreement with those of bacteriocin or carotovoricin.  相似文献   

12.
Head rot is a major disease of broccoli caused by the soft rot pathogens Pseudomonas fluorescens and Erwinia carotovora. Two in vitro pathogenicity tests were evaluated as a methods to identify broccoli cultivars susceptible or resistant to bacterial head rot. One test used mature heads excised from the plant and inoculated with squares of cotton lint which had been soaked in a bacterial suspension. The other test involved stab-inoculating axenically grown seedlings. With the excised head test, susceptible cultivars showed a black soft rot, whilst less susceptible or moderately resistant cultivars showed only watersoaking, or browning and slight softening of the tissue. No cultivar was completely resistant. Ten cultivars were tested, and their susceptibility ratings corresponded with previously recorded field data, with one exception. This laboratory test could be used to screen for susceptibility to head rot in broccoli breeding programmes. The seedling test distinguished differences in aggressiveness among bacterial isolates but not cultivar susceptibility. Increasing head size correlated negatively with disease resistance. Head shape, i.e. cultivars which showed a domed shape rather than a flat shape, was positively correlated with disease resistance. Thus small domed heads are more resistant to head rot than large flat heads. Other morphological characteristics, viz. floret prominence and number, and sepal stomatal number were not correlated with host resistance.  相似文献   

13.
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is vectored by Polymyxa betae. The disease can only be controlled by growing partially resistant sugar beets, which quantitatively reduce virus replication and spread. None of the known major resistance genes (Rz1, Rz2, Rz3), alone or in combination, are able to prevent BNYVV infection entirely. Here we report for the first time the identification of a Spanish soil, containing an A-type BNYVV with RNA 1-4, displaying Rz1 resistance-breaking abilities comparable to soils from the USA and to those from France containing the French (Pithiviers) P-type BNYVV with RNA 5. A resistance test with several soil samples vs. different sugar beet cultivars was conducted under standardised conditions. Sugar beets were analysed after 12 weeks of greenhouse cultivation for taproot weight, BNYVV and relative P. betae content. The soil samples from Spain, France and the USA produced high virus contents and strong rhizomania symptoms in Rz1 plants, indicative of resistance-breaking abilities. In addition, all resistance-breaking soil samples produced detectable virus concentrations in plant lateral roots of the Rz1 + Rz2 cultivar, and plants grown in the Spanish soil sample also had reduced taproot weight and displayed severe rhizomania disease symptoms. Additionally, the main pathogenicity factor P25, responsible for the formation of BNYVV symptoms, showed high sequence variability in the amino acid tetrad at position 67–70. The results suggest the geographically independent selection of BNYVV resistance-breaking isolates following the uniform cultivation of Rz1-containing sugar beet cultivars.  相似文献   

14.
The morphology of apple and pear stigma was investigated with confocal laser scanning microscopy and scanning electron microscopy. The floral colonization process by Erwinia amylovora was studied with gfp-labelled bacteria and confocal laser scanning microscopy to allow the in vivo observation of the pathogen colonization on intact, viable plant tissues without any kind of staining of the specimens. The interaction on the stigma between Erwinia amylovora and Pantoea agglomerans, both labelled with genes encoding for fluorescent proteins (DsRed-GFP), was also investigated. A stylar groove, covered by papillae and dwelling from the stigma along the style, was visualized. In laboratory conditions, this groove was shown to be an important way for E. amylovora migration towards the nectarthodes. Due to its anatomical structure the groove can sustain bacterial multiplication and thus may play an important role on the interactions between the pathogen and the bacterial antagonist P. agglomerans.  相似文献   

15.
Many fusiform ascospores observed on soybean seeds with yeast spot disease symptoms differed significantly from those of Eremothecium coryli, the known causal agent of yeast spot disease in soybean. On the basis of morphological and physiological characteristics and sequence data of the internal transcribed spacer regions including the 5.8S rDNA and D1/D2 regions of 26S rDNA, this fungus was identified as E. ashbyi. Pathogenicity of E. ashbyi was confirmed by reinoculation test. This report is the report on E. ashbyi causing soybean yeast spot disease. In addition, this study showed that E. ashbyi was transmitted by the stink bug, Riptortus clavatus, as was E. coryli, the two Eremothecium yeasts may have been acquired when the stink bug fed on infected soybeans and overwintered in this insect species. The nucleotide sequence data reported are available in the GeneBank/EMBL/DDBJ database as accessions AB294407 to AB294412 for E. ashbyi EA1, EA7 and EA11.  相似文献   

16.
Leaf spots were found on Christmas rose (Helleborus niger) in Yamagata Prefecture, Japan, in October 2006. The morphology of the causal fungus was very close to that of Colletotrichum truncatum. Classifying the species from the sequences of the internal transcribed spacer regions of ribosomal DNA was inconclusive, and the isolates were identified only as Colletotrichum sp. Artificial inoculation confirmed the pathogenicity of isolates to the host plant and some legumes. We propose the name anthracnose of Christmas rose for this disease by Colletotrichum sp.  相似文献   

17.
Quorum sensing is a regulatory mechanism that connects gene expression to cell density in bacteria. Amongst proteobacteria, numerous functions are regulated in this way, including pathogenicity in the Enterobacteriaceae genus Pectobacterium. In Pectobacterium, the signalling molecules involved in this regulatory process belong to the N-acyl-homoserine lactone class. Over the last 6 years, various studies have shown that these signal molecules could be degraded by other bacteria or by plant and animal cells, opening the path to innovative biocontrol strategies. This review explores the various determinants of pathogenicity in Pectobacterium and describes approaches that have been developed to quench the quorum-sensing-dependent pathogenicity in Pectobacterium. These approaches range from signal degradation by physicochemical constraints to the identification of signal-sensing inhibitors and from the identification of enzymes degrading acyl-homoserine lactones to the construction of transgenic plants tolerant to Pectobacterium.  相似文献   

18.
Erwinia pyrifoliae, the causal pathogen of shoot blight in the Asian pear tree (Pyrus pyrifolia cv. Singo), is host-specific and endemic to Korea. To identify the genes associated with the hypersensitive response (HR) and pathogenicity, a genomic library of E. pyrifoliae WT3 was constructed, and the cosmid clone Escherichia coli (pCEP33) was selected. Sequence analysis of 19.7-kb pCEP33 determined disease-specific (dsp) region homolog and approximately 40% of the hrp genes, which included hrpW, hrpNEp, hrpV, hrpT, hrcC, hrpG, hrpF, and partial hrpE homologs, with respect to the cluster of Erwinia amylovora. Additionally, two open reading frames, ORFD and ORFE, were found downstream of the dspEF region. The results of the sequence analysis showed that the pCEP33 did not contain any hrp regulatory genes or most of the genes encoding components of the Hrp protein secretion system. The hrpNEp gene of E. pyrifoliae contained five intergenic nucleotide fragment insertions (INFIs) and produced the HR elicitor protein harpinEp, with a molecular mass of approximately 44kDa. The purified HrpNEp protein elicited faster and stronger HR when infiltrated into tobacco leaves than did HrpNEa from E. amylovora. To observe the role of the hrpL gene in the expression of HrpNEp, the pEL2 containing hrpL was used to transform E. coli (pCEP33). Expression of HrpNEp in E. coli (pCEP33 + pEPL2) was detected with an immunoblot using antiserum raised against HrpNEp, indicating a role of hrpL gene in enhancing the expression of HrpNEp.  相似文献   

19.
Previously, we showed that the sugar transporter MfsX in the major facilitator superfamily is involved in the pathogenicity of Dickeya dadantii (syn. Erwinia chrysanthemi). Here, we show that a mutation in this gene resulted in increased susceptibility to several antimicrobial agents, reduced biosynthesis of a blue pigment indigoidine, and reduced chemotaxis towards some sugars and amino acids and in pellicle formation. These phenotypes in D. dadantii have been thought to be important for survival in planta. Thus, this MfsX sugar transporter may contribute to pathogenicity by enhancing in planta survival of the phytopathogen.  相似文献   

20.
In 1991 and 1992, 12 potato cultivars were screened at two locations for resistance to blackleg, after vacuum infiltration of the seed withErwinia carotovora subsp.atroseptica orE. chrysanthemi. Cultivar differences for resistance toE.c. subsp.Atroseptica andE. chrysanthemi were found which were consistent over locations and years. Seed tubers of the same cultivars were also screened for resistance to bothErwinia spp. by using a tuber slice inoculation method. Correlation coefficients for comparisons between resistance to blackleg in the field and tuber tissue resistance under aerobic or anaerobic conditions were not significant. This could partly be explained by drastic changes in relative tuber tissue resistance of the cultivars within a 5 weeks period after planting in the field. Presprouting of seed tubers in diffuse daylight had a less pronounced effect on relative tuber tissue resistance than planting in the field. Monitoring the process of mother tuber decay during the growing season of 1993 after vacuum infiltration withE.c. subsp.atroseptica andE. chrysanthemi revealed that cultivars differed in the extent to which these bacteria enhanced the process of mother tuber decay. These differences partly explained the cultivar differences for resistance to blackleg in the field.Abbreviations Eca Erwinia carotovora subsp.atroseptica - Ech Erwinia chrysanthemi - NOP Noordoostpolder - Wag Wageningen  相似文献   

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