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1.
Bacterial leaf blight of aroids is caused by a heterogeneous group of xanthomonads listed as Xanthomonas axonopodis pv. dieffenbachiae (Xad) on the EPPO A2 quarantine list. Recently, Xad strains were shown not to belong to X. axonopodis but to the species X. citri, X. phaseoli and X. euvesicatoria. Here, to verify the pathovar designation, 11 representative strains were tested for pathogenicity on six aroid genera. They had overlapping host ranges and only the strain isolated from Syngonium showed host specificity. The X. citri strains, isolated from various hosts, showed dissimilarity in virulence to the tested aroid genera. The X. phaseoli strains, isolated from Anthurium and Syngonium, were generally more virulent and, additionally, induced systemic infections. The X. euvesicatoria strains, isolated from Philodendron, were scored as not pathogenic on the tested aroids. Four representative strains were genome sequenced and showed a variable virulence‐associated gene content. Pathogenicity to aroids was correlated with the presence of three specific T3 effector genes and with a T6SS gene sequence. Together, the phylogenetic and pathogenic differentiation among Xad strains justifies the installation of three pathovar epithets for the pathogens on aroids: X. phaseoli pv. dieffenbachiae comb. nov. for the strains isolated from Anthurium; X. phaseoli pv. syngonii comb. nov. for the strain isolated from Syngonium; and X. citri pv. aracearum comb. nov. for the strains isolated from Aglaonema, Xanthosoma and Dieffenbachia. It is proposed that phytosanitary regulations for xanthomonads on aroids are restricted to these three pathovars.  相似文献   

2.
Fifty-five strains of Xanthomonas axonopodis pv. vignicola, isolated from blight and pustule symptoms of cowpea leaves, originating from 11 countries, were characterized for their carbon-source metabolization pattern using the Biolog GN microplate system. Great variation was found between strains according to origin. Dextrin, glycogen and succinamic acid were not used by strains from Benin, Uganda or Thailand, but by all the other strains (excluding two strains from Mozambique), whereas N-acetyl-D-glucosamine and malonic acid were used by the strains from Benin, Uganda and Thailand, but generally not by the other strains. The strains from Benin, Uganda and Thailand, as well as strains from Venezuela, Brazil and Mozambique, clustered separately from the others in multivariate analysis. Nineteen substrates were used by all the strains, 47 not by any strain and 29 only by some strains. No considerable differences were found between strains isolated from blight symptoms and from pustules. Virulence of strains was not related to the metabolic pattern. The Biolog database was not representative of the diversity of X. axonopodis pv. vignicola, since all strains were identified as Xanthomonas campestris, although belonging to eight pathovars, while only eight of nine strains from Benin and both strains from Thailand were identified as X. campestris pv. vignicola. The Biolog system appeared to be useful for characterizing the diversity of X. axonopodis pv. vignicola strains. A set of representative strains based on metabolic and molecular diversity, virulence and geographic origin is suggested for screening for resistant cowpea cultivars.  相似文献   

3.
Xanthomonas axonopodis pv. dieffenbachiae, the causal agent of bacterial blight of Araceae (aroids), is a regulated pest in several countries and is included in the EPPO A2 List. Reference strains of Xanthomonas axonopodis pv. dieffenbachiae have recently been reclassified into the species Xanthomonas phaseoli, Xanthomonas citri and Xanthomonas euvesicatoria on the basis of different features, including multilocus sequence analysis, average nucleotide identity and homology in DNA–DNA hybridization analyses. Based on pathogenicity tests, Constantin et al. (2017) proposed naming the pathogens on aroids as X. phaseoli pv. dieffenbachiae, X. phaseoli pv. syngonii and X. citri pv. aracearum. Recommendations are made on how to deal with these changes for the group of pathogenic bacteria for Araceae. The name Xanthomonas axonopodis pv. dieffenbachiae on the EPPO List should be adjusted to the names proposed in the taxonomic study by Constantin et al. (2016). The current EPPO Diagnostic Standard is directed at strains pathogenic on Anthurium. They mainly belong to X. phaseoli pv. dieffenbachiae, but some also to X. citri pv. aracearum that are not detected by the EPPO Diagnostic Standard. Xanthomonas phaseoli pv. syngonii strains are also aggressive, but with a host range restricted to Syngonium. The pathogenicity specific to aroids of the bacterial isolates reclassified as Xanthomonas euvesicatoria was not confirmed and no pathovar epithet has been retained for these strains.  相似文献   

4.
A new bacterial disease of Persian (English) walnut (Juglans regia) has been observed in France. This disease, called vertical oozing canker (VOC), is characterized by vertical cankers on trunks and branches of affected walnut trees with oozing exudates. To determine the aetiology of the disease, a study was carried out in 79 walnut orchards and nurseries located in southeastern and southwestern France. Bacterial analysis from diseased samples yielded 36 strains identified as Xanthomonas arboricola and 32 strains identified as Brenneria nigrifluens on the basis of biochemical tests. The causal agent of VOC was identified as X. arboricola by pathogenicity tests on walnut. Fluorescent amplified fragment length polymorphism (F‐AFLP) was carried out on 36 strains of X. arboricola collected in this study, 24 strains of X. arboricola pv. juglandis isolated from walnut blight symptoms and one strain of X. arboricola pv. corylina included as an outgroup. Based on cluster analysis of F‐AFLP data, most X. arboricola strains responsible for main VOC outbreaks showed a high degree of similarity, forming a cluster clearly separate from strains of X. arboricola pv. juglandis isolated from walnut blight symptoms. It is suggested that VOC is caused by a distinct genetic lineage within the pathovar juglandis of X. arboricola that is also able to cause classical bacterial blight symptoms on walnut leaves and fruits.  相似文献   

5.
Bacterial blight, caused by Xanthomonas axonopodis pv. dieffenbachiae (Xad), is a major threat to the anthurium cut flower industry worldwide. Two field trials in Hawaii evaluated the long-term persistence of Xad in artificially-infested crop residues. Xad survived in leaf, petiole, and root residues for as long as 4 months when tissues were left on the surface or buried 15cm deep. Survival was considerably shorter (approximately 20 days) outside of residues. Xad that was recovered from residues over a period of 4 months retained pathogenicity. Xad was isolated from living roots of naturally-infected plants which further suggests that roots left in the field after culling may be particularly important, but overlooked, inoculum source. This information is key to determining minimum fallow periods before replanting devastated fields.  相似文献   

6.
为筛选具有广谱拮抗作用的内生菌,采用平板对峙法从健康红掌组织中分离和筛选对多种病原菌有拮抗作用的内生菌株,选择拮抗作用较好的菌株进行抑菌谱和拮抗作用测定,通过形态学特征、生理生化特性和分子生物学特征对其进行鉴定,利用盆栽试验测定其对红掌的促生作用和对红掌细菌性疫病的防效。结果显示,在健康红掌中共分离得到237株内生细菌,其中菌株Y-54的拮抗作用最强,其50倍发酵液对红掌细菌性疫病菌Xanthomonas axonopodis pv. dieffenbachiae的抑制作用最强,抑制率达37.78%;同时对多种病原真菌具有较强的抑制作用,其中对番茄叶霉病菌Cladosporium fulvum的抑制率达86.42%。结合形态学特征、生理生化特性和分子生物学特征将菌株Y-54鉴定为暹罗芽胞杆菌Bacillus siamensis。菌株Y-54的50倍发酵液可显著提高红掌叶长、叶宽和叶绿素相对含量(soil and plant analyzer development,SPAD)值,施药14 d和28 d后对红掌细菌性疫病的防效分别为62.94%和59.56%,与对照药剂的防效相当,表明菌...  相似文献   

7.
One of the most devastating Xanthomonas diseases affecting the Anthurium cut flower industry worldwide is the bacterial blight caused by Xanthomonas axonopodis pv. dieffenbachiae (Xad). The disease can be spread through latently infected tissue-cultured plants that are used for the propagation of Anthurium worldwide. Current disease diagnostic techniques involve the use of semi-selective media and serological tests. This study describes the development of a PCR tool combined with a genus-specific monoclonal antibody for the sensitive detection of the pathogen directly from plants. It was demonstrated that the immunocapture PCR (IC-PCR) was more sensitive than the conventional PCR and even more sensitive than indirect ELISA for the detection of the pathogen. Latently infected plants could be positively screened for the presence of the pathogen. Three sets of primers were designed from DNA probes that were reported to show some specificity to the pathovar dieffenbachiae. The use of all three sets of primers in a single reaction successfully amplified the three individual loci when bacterial DNA was used as a template. The multiplex PCR generated PCR profiles that could differentiate between the reference strains of X. axonopodis pv. dieffenbachiae from other control bacteria. The new primers could therefore be used both for the diagnosis of Anthurium blight in single PCR reactions and also for the profiling of Xanthomonas. pv. dieffenbachiae strains using the multiplex PCR technique.  相似文献   

8.
Since 2008, bacterial canker of kiwifruit (Actinidia deliciosa and A. chinensis) caused by Pseudomonas syringae pv. actinidiae (Psa) has resulted in severe economic losses worldwide. Four biovars of Psa can be distinguished based on their biochemical, pathogenicity and molecular characteristics. Using a range of biochemical, molecular and pathogenicity assays, strains collected in France since the beginning of the outbreak in 2010 were found to be genotypically and phenotypically diverse, and to belong to biovar 3 or biovar 4. This is the first time that strains of biovar 4 have been isolated outside New Zealand or Australia. A multilocus sequence analysis based on four housekeeping genes (gapA, gltA, gyrB and rpoD) was performed on 72 strains representative of the French outbreak. All the strains fell into two phylogenetic groups: one clonal corresponding to biovar 3, and the other corresponding to biovar 4. This second phylogenetic group was polymorphic and could be divided into four lineages. A clonal genealogy performed with a coalescent approach did not reveal any common ancestor for the 72 Psa strains. Strains of biovar 4 are substantially different from those of the other biovars: they are less aggressive and cause only leaf spots whereas Psa biovars 1, 2 and 3 also cause canker and shoot die‐back. Because of these pathogenic differences, which were supported by phenotypic, genetic and phylogenetic differences, it is proposed that Psa biovar 4 be renamed Pseudomonas syringae pv. actinidifoliorum pv. nov. Strain CFBP 8039 is designated as the pathotype strain.  相似文献   

9.
During 1997 and 1998, serious outbreaks of bacterial leaf spot disease were observed on zinnia plants grown in home and commercial gardens in Ohio, USA. Twenty-two strains of Xanthomonas campestris pv. zinniae, isolated from diseased zinnia plants and contaminated seeds, were identified based on morphological, physiological and biochemical tests, fatty acid methyl ester analyses and pathogenicity tests on zinnia cv. Scarlet. Host range studies indicated that all of the X. campestris pv. zinniae strains were pathogenic on zinnia and tomato, but not on cabbage, lettuce, pepper and radish. The phenotypic and genotypic relationships among the strains determined based on serological reaction pattern, fatty acid profiles, repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) fingerprints and sequence analysis of the 16S–23S rDNA spacer region suggested that X. campestris pv. zinniae strains were closely related to each other, but clearly distinct from other Xanthomonas species including X. campestris pv. campestris, X. axonopodis pv. vesicatoria, X. vesicatoria and X. hortorum pv. vitians tested in this study. The results also demonstrated that rep-PCR fingerprinting is rapid, reliable and the most practical method for routine detection and identification of X. campestris pv. zinniae strains.  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 semi-selective medium for isolation of Xanthomonas axonopodis pv. vignicola from cowpea (Vigna unguiculata) plant and soil samples was developed. Twelve carbon and five nitrogen sources were tested with four strains of X. axonopodispv.vignicola, and 25 antibiotics were screened against saprophytes. -cellobiose (10g) was selected as the optimal carbon source. Among the antibiotics, cefazoline inhibited growth of most of the saprophytes with little effect on strains of the pathogen. ,-methionine enhanced growth of X. axonopodispv.vignicola. Boric acid along with ammonium chloride suppressed growth of Pseudomonas fluorescens. The semi-selective medium designated as cefazoline-cellobiose-methionine (CCM) medium contained K2HPO4 1.34g, KH2PO4 0.4g, MgSO4 0.3g, H3BO3 0.2g, NH4Cl 1.0g, -cellobiose 10g, cycloheximide 0.2g, ,-methionine 1.0g, cefazoline 10mg and agar 14g per l of water (pH 7.2). Colonies of X. axonopodispv.vignicola on CCM medium were whitish, round, raised and 0.2–1.8mm in diameter 96h after incubation. CCM medium generally inhibited growth of Pantoea agglomerans, Bacillus subtilis and saprophytes isolated from cowpea leaves. Colonies of Pseudomonas fluorescens and a saprophytic bacterium, which were not completely suppressed by CCM, could be differentiated from X. axonopodispv.vignicola by their smaller size and different color. The CCM medium proved useful for isolation of X. axonopodispv.vignicola from cowpea plant and soil samples. This is the first report of a semi-selective medium developed for detection of X. axonopodispv.vignicola.  相似文献   

12.
A multilocus sequence analysis (MLSA) was performed on five housekeeping genes (fusA, gapA, gltA, lacF and lepA) of 22 Xanthomonas euvesicatoria strains recently isolated from alfalfa, pepper and tomato plants in Iran. In addition, 161 strains isolated worldwide from pepper, poinsettia, rose and tomato plants were included in the analysis. All X. euvesicatoria pv. perforans isolates from tomato plants in Iran clustered in a monophyletic group, although five MLSA haplotypes were detected among them. The Iranian tomato strains presented 10 nucleotide differences in the lepA gene sequences compared to the known worldwide population of X. euvesicatoria pv. perforans. Statistical analyses revealed a recombination event that had occurred in the lepA gene of the strains isolated from tomato in Iran. BOX‐PCR analysis confirmed the inclusion of Iranian tomato strains within X. euvesicatoria pv. perforans. Furthermore, X. euvesicatoria pv. euvesicatoria strains isolated from pepper in Iran differed in one nucleotide in the lepA gene sequence from the known worldwide population of the pathovar, and clustered in a group containing strains isolated in Nigeria. The strains isolated from alfalfa in Iran clustered with the type strain of X. euvesicatoria pv. alfalfae. Altogether, the results reveal the existence of a phylogenetically novel population of X. euvesicatoria pv. perforans in Iran which needs further in‐depth analysis to pinpoint the epidemiological impact of these strains.  相似文献   

13.
构树上一种新的丁香假单胞菌致病变种的研究   总被引：1，自引：1，他引：1  
 构树细菌性疫病是一种荧光假单胞菌引起的新病害。主要症状有叶片角斑,嫩梢肿大和幼枝溃疡。从江苏一带分离获得的12个构树菌株和3个桑树对比菌株进行交互接种试验,发现构树菌株与桑树菌株之间不能交互侵染其寄主。细菌学特征和LOPAT试验及其它37项生理生化和营养特性试验表明,两种菌的表型特征基本相似,仅在7种化合物的利用上存在差异。两种菌的血清学反应无相关性。细胞全蛋白SDS一聚丙烯酰胺凝胶电泳图谱也略有不同。试验结果证明,构树细菌性疫病细菌属于假单胞菌属(Pseudomonas),丁香假单胞菌(P.syringae)的一个新致病变种,定名为Pseudomonas syrzngae pv.broussonetiae pv.nov.  相似文献   

14.
Yellow-pigmented bacteria isolated from blight-affected pomegranate leaves and fruit across seven Indian states in epidemics during the years 2008–2016 were characterized and identified using phenotypic and genotypic tools. All bacterial isolates shared phenotypic traits such as colony morphology, NaCl and pH sensitivity and fuscan production, and caused typical lesions on pomegranate plants upon artificial inoculation. Analysis of 16S ribosomal DNA and 16S–23S rDNA intergenic spacer sequences confirmed their identity as Xanthomonas axonopodis pv. punicae. The new isolates collected after 2000 were compared with an old isolate from the 1950s using polyphasic taxonomic approaches including multilocus sequence analysis (MLSA). Nucleotide polymorphism in 24 isolates for nine genomic loci (dnaK, fyuA, gyrB (Young), gyrB (Almeida), rpoD, fusA, gapA, gltA and lepA) showed minor variations in loci fyuA and gyrB. Isolates were grouped into four nearly identical sequence types, ST1, ST2, ST3 and ST4, based on their allelic profiles, ST3 being widespread in Indian states. Molecular phylogenetic analysis of concatenated 5690 bp with other Xanthomonas pathovars revealed its close genetic similarity with the X. citri group. The blight outbreak in diverse geographical locations is attributed to a re-emerged clonal population of X. axonopodis pv. punicae on a genetically homogenous pomegranate cultivar. The latently infected vegetative planting material of elite pomegranate cultivars contributed to the dissemination of the bacterial inoculum. This study highlights and forewarns of the role played by the clonally propagated elite pomegranate cultivars in disseminating and sustaining clonal populations of this bacterial plant pathogen in many Indian states.  相似文献   

15.
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16.
A number of bacterial pathogens have previously been shown to cause blight and die‐back of Eucalyptus species. These include Pantoea ananatis, Pseudomonas cichorii, Xanthomonas axonopodis and Xanthomonas dyei pv. eucalypti. In 2003 a newly established compartment of a Eucalyptus grandis clone in the Mtunzini area of South Africa showed extensive leaf blight and die‐back. The plantation was located in an area where sugarcane is extensively cultivated. Bacteria were commonly found exuding from leaves and petioles. Numerous insects in the family Miridae were observed in the plantation and collected. Isolations from diseased material and mirid insects yielded two distinct bacterial species. The objectives of this study were to identify these bacterial species and determine their aetiology. Phenotypic methods as well as 16S rRNA and gyrB sequencing were performed on all isolates, confirming the presence of P. ananatis and Xanthomonas vasicola, of which the pathovar vasculorum (Xvv) is known to infect sugarcane and maize. Xanthomonas vasicola isolates from E. grandis and a strain of Xvv, previously isolated from sugarcane, were inoculated into the susceptible Eucalyptus clone and three sugarcane cultivars. All isolates were found to be pathogenic. This study thus suggests that X. vasicola has made a significant host jump from sugarcane to eucalypts in South Africa.  相似文献   

17.
In June of 1998, a new bacterial disease was observed on Welsh onion in Okinawa Prefecture, Japan. Infected plants in nursery boxes were stunted with tip dieback, and heavily infected plants died. In fields, the disease appeared on leaves as irregular gray spots or elliptical spots with creases in the center. These spots enlarged and spread rapidly continued cloudy or rainy weather, and formed blight lesions on outer leaves. Yellow mucoid bacterial colonies were consistently isolated from these lesions. The causal bacterium was identified as a pathovar of Xanthomonas campestris on the basis of bacteriological properties. The bacterium was pathogenic to Welsh onion, onion, but nonpathogenic to chive, Chinese chive and hyacinth. Of Liliaceae plants, which contain Welsh onion and onion, only hyacinth has been reported as a host for the genus Xanthomonas, namely X. campestris pv. hyacinthi. However, strains of X. campestris pv. hyacinthi were not pathogenic against either Welsh onion or onion. From these results, the bacterium isolated from Welsh onion is considered to be a new pathovar of X. campestris, and the name of X. campestris pv. allii pv. nov. is proposed. A strain MAFF 311173 is designated as the pathotype strain. Received 29 March 2000/ Accepted in revised form 4 July 2000  相似文献   

18.
Bacterial blight is a highly devastating disease caused by Xanthomonas axonopodis pv. punicae, recording 60 to 80 percent yield-loss of pomegranate in India. In the present investigation, a total of 209 genotypes including 105 exotic types from USDA, 66 wild types and 38 cultivated types from India were screened and categorized into fifteen clusters using cluster and principal component analysis. Genotypes of cluster 15, viz. 108 B and 99 A from USDA and 318734, Daru-18 and IIHR-30 from India, were found to be resistant to bacterial blight while genotypes of cluster 9 were highly susceptible. Two genotypes, each from cluster 15 (318734) and 9 (Ruby), were compared for biochemical and histological parameters to understand the defense mechanism. Significantly, higher accumulation of defense related metabolites, viz. total phenol, flavonoid and antioxidant contents, were observed in resistant genotype (318734). Fewer numbers of stomatal pores that served as portals of entry for plant pathogens were recorded in this genotype. Resistance observed in genotype 318734 might be due to an incompatible interaction between host and pathogen compared to other genotypes. This is the first report of putative resistance sources in pomegranate against Xanthomonas axonopodis pv. punicae.  相似文献   

19.
Guggal (Commiphora wightii (Arnott) Bhandari comb. nov.) is a small tree which is tapped for medicinally important oleo?Cgum?Cresin. Naturally infected plant oozes oleo?Cgum?Cresin from its trunk and primary branches. However, in either case, the plant dies slowly after oozing. A bacterium was established to be responsible for these phenomena. Four isolates of this bacterium were characterised by biochemical tests, Biolog GN2 microplate reaction, rDNA sequencing, which suggested that the pathogen belonged to the genus Xanthomonas. However, phylogenetic analysis based on chaperone protein (dnaK) gene, TonB?Cdependent receptor (fyuA) gene, DNA gyrase B (gyrB) gene and RNA polymerase sigma factor (rpoD) gene sequences placed it as a member of X. axonopodis 9.2 rep?CPCR/DNA?CDNA homology cluster close to X. perforans, X. alfalfae and X. euvesicatoria. Further elucidation of phylogenetic position of the test strains was achieved from a gyrB based tree considering sequences from 71 representative strains. Test strains were confirmed to be members of X. axonopodis. These had very narrow infectivity limited to Commiphora spp. Hence, we propose a novel pathovar, X. axonopodis pv. commiphoreae pv. nov. as the cause of gum oozing in guggal. Pathotype is DXA 01 = CFBP 7580 = LMG 26789.  相似文献   

20.
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   

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