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1.
Molecular characterization of the Cassava brown streak virus coat protein   总被引：1，自引：0，他引：1  
A partial sequence of 1114 nucleotides of a virus from cassava brown streak diseased (CBSD) material was obtained. Alignment of the predicted amino acid sequence with those of other members of the Potyviridae showed closest identity with the coat protein of Sweet potato mild mottle virus (genus Ipomovirus ). The predicted amino acid sequence has one open reading frame with a 3' untranslated region of 144 nucleotides and a poly(A) tail. The expressed protein was shown to cross-react with an antiserum raised previously to a virus isolated from CBSD material. Evidence presented suggests that CBSD is caused by Cassava brown streak virus , a tentative member of the genus Ipomovirus , as this virus is consistently found associated with CBSD.  相似文献   

2.
A partial sequence of Oat mosaic virus (OMV) has been obtained for four isolates of the virus from four European countries. This represents the first available sequence data for this important disease of winter-sown oats. The longest clone of 1699 nucleotides was obtained from infected English oats using a degenerate primer, designed to members of the Potyviridae family. Alignment of the predicted amino acid sequence with members of the Potyviridae showed closest identity with viruses of the Bymovirus genus. The predicted amino acid sequence has one open reading frame corresponding to part of the NIb and capsid protein, with a 3 untranslated region of 351 nucleotides, followed by a poly(A) tail. PCR primers were designed to the coat protein and NIb gene of members of the Bymovirus genus and used to obtain partial sequences of 1441 nucleotides at the 3 end of infected oats from both Wales and France. A specific primer set designed to the English isolate was used to generate a product of 701 nucleotides from OMV-infected oat leaves from Ireland. All four isolates are highly conserved at the amino acid level.The first two authors contributed equally to the work  相似文献   

3.
Jiong Chen  Sohn  Chen  Lei  Cheng  Schulze  Steinbiss  Antoniw  & Adams 《Plant pathology》1999,48(5):642-647
To study the variation between wheat bymovirus isolates and to resolve uncertainties about the identity of the virus in some countries, leaves of infected plants were obtained from nine sites in China and from one each in Italy, Germany, USA and Canada. The German isolate was obtained from rye and the Canadian isolate was the type strain of wheat spindle streak mosaic virus (WSSMV). In RT-PCR, using primers designed from a partial sequence of a French isolate (tentatively described as WSSMV), genome fragments were obtained from the Italian and the French isolates but not from the Chinese ones. Conversely, products were consistently obtained from the Chinese isolates, but not from the Italian or French ones, when primers were designed from the sequence of a Japanese isolate of wheat yellow mosaic virus (WYMV). Nucleotide sequences were obtained from regions at or near the 3'-terminus of RNA1 of six Chinese isolates and the four from Europe and North America, usually including the coat protein. Nucleotide and amino acid sequence comparisons demonstrated that the European and North American isolates were extremely similar and were therefore WSSMV, while the Chinese isolates were close to the Japanese isolate and were thus WYMV.  相似文献   

4.
Wisteria mosaic, a serious disease of Wisteria spp. in horticultural production in many parts of the world, is caused by a virus, Wisteria vein mosaic virus (WVMV). This paper reports the presence of the virus in a new host, Wisteria venusta , and a new geographical distribution, New South Wales, Australia. A partial sequence (1329 nucleotides) of this isolate of WVMV was obtained, which represents the first available sequence data for the virus. Alignment of the nucleotide and predicted amino acid sequences with those of members of the Potyviridae showed closest identity with viruses of the Potyvirus genus. The predicted amino acid sequence has one open reading frame, open at the 5' end, corresponding to part of the nuclear inclusion b protein and the capsid protein, followed by a 251-nucleotide untranslated region and a polyadenylated tail at the 3' end.  相似文献   

5.
Soybean vein necrosis-associated virus (SVNaV) is a newly isolated tospovirus from field-grown soybeans in the United States. Polyclonal antibodies generated against the recombinant Escherichia coli-expressed nucleocapsid protein (NP) of the virus, reacted specifically with SVNaV and exhibited low, if any, cross-reactivity with other species within the genus Tospovirus. The serological results are in agreement with low sequence homology of the SVNaV-NP gene when compared with those of other tospovirus species, some of which are capable of infecting soybean naturally. Phylogenetic analysis utilizing NP sequences from several SVNaV isolates collected from different geographical regions and various soybean genotypes over 4?years showed close relationships, but distinct from the representatives of all the established serogroups or distinct serotypes within the genus of Tospovirus. All SVNaV isolates examined reacted strongly with the generated polyclonal antibodies. Collectively, our serological analyses suggest that SVNaV represents a new and distinct soybean-infecting tospovirus serotype. Furthermore, our data demonstrate that antiserum against NP has the potential to serve as a reliable probe for SVNaV detection in field-grown soybeans.  相似文献   

6.
ABSTRACT A polymerase chain reaction-restriction fragment length polymorphism assay to distinguish Tilleita walkeri, a rye grass bunt fungus that occurs in the southeastern United States and Oregon, from T. indica, the Karnal bunt fungus, is described. The internal transcribed spacer (ITS) region of the ribosomal DNA repeat unit was amplified and sequenced for isolates of T. indica, T. walkeri, T. horrida, and a number of other taxa in the genus Tilletia. A unique restriction digest site in the ITS1 region of T. walkeri was identified that distinguishes it from the other taxa in the genus. Phylogenetic analysis of the taxa based on ITS sequence data revealed a close relationship between T. indica and T. walkeri, but more distant relationships between these two species and other morphologically similar taxa.  相似文献   

7.
A method was developed for the detection of viruses from the genus Potexvirus. Following alignment of full-length RNA sequences and deduced amino acid sequences of 10 different viruses from the genus Potexvirus, a number of conserved sequence motifs were identified in the viral replicase-encoding region. Seven different primers based on these motifs were tested for their efficiency as potexvirus group-specific cDNA and/or PCR primer. Several combinations of primers proved capable of generating DNA fragments for each of six different potexviruses tested. One cDNA primer in combination with one PCR primers set proved most successful in reliably generating discrete PCR products. Application of this set to a number of different potexviruses, some for which no sequence data had been published yet, resulted in amplification of virus-specific PCR products for all viruses tested. Sequence analysis of cloned PCR products confirmed their identity. This general potexvirus primer set can be useful for the identification of (unknown) potexvirus infections.  相似文献   

8.
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9.
A sterile white fungus was isolated from the healthy looking roots of buffalo grass (Stenotaphrum secundatum) grown on cleared bush land in Perth, Western Australia. The fungal strain was pathogenic on 12 plant species screened under the greenhouse conditions. The clamp connections and dolipore septa indicated that the isolate was a Basidiomycete. Mycelial features, growth rate at different temperatures, as well as pathogenicity patterns of this sterile white basidiomycete (SWB) were distinctly different from those of a strain with a similar morphology, ATCC 28344, previously described as a pathogen in Florida and Georgia (USA). All attempts to induce sporulation failed. The isolates were also compared using the nucleotide sequence analysis of the ribosomal DNA array. Approximately 1 kbp of the 5 end of the large subunit ribosomal RNA gene, complete sequences of the small subunit ribosomal RNA gene and the entire ITS region (including ITS1, ITS2 and 5.8S gene) were sequenced for the purpose. The obtained sequences were compared with the homologous regions of other genera of Agaricales available in GenBank. Relatively low sequence similarities between the American and Australian strains, as well as the phylogenetic analysis of the studied regions has suggested that these two fungi belong to different genera. Interesting results were achieved in the case of the large subunit ribosomal DNA since this region has been widely studied for taxonomy of Basidiomycetes. The Australian strain 3034 appeared to be closely related to the genus Campanella and the American SWB was identified as belonging to the genus Marasmius, possibly to M. graminum. Our data suggest that the Australian strain is a novel pathogen, and is different from the American SWB isolates described to date.  相似文献   

10.
Sequences representing the genomes of two distinct virus isolates infecting wild plants of two members of the genus Drakaea (hammer orchids) in Western Australia are described. The virus isolated from Drakaea livida has a bipartite genome of 4490 nt (RNA1) and 2905 nt (RNA2) that shares closest sequence and structural similarity to members of the genus Pecluvirus, family Virgaviridae, described from legumes in the Indian subcontinent and West Africa. However, it differs from pecluviruses by lacking a P39 protein on RNA2 and having a cysteine‐rich protein gene located 3′ of the triple gene block protein genes. It is the first peclu‐like virus to be described from Australia. The name Drakaea virus A is proposed (DVA; proposed member of the family Virgaviridae, genus unassigned). The second virus isolate was identified from Drakaea elastica, a species classed as endangered under conservation legislation. The genome sequence of this virus shares closest identity with isolates of Donkey orchid symptomless virus (DOSV; proposed member of the order Tymovirales, family and genus unassigned), a species described previously from wild Caladenia and Diuris orchids in the same region. These viruses are the first to be isolated from wild Drakaea populations and are proposed to have an ancient association with their orchid hosts.  相似文献   

11.

Rose yellow mosaic virus, which belongs to the Roymovirus genus in the Potyviridae family, was isolated here in Japan from a rose cultivar, Irish Mist. The full-length genomic sequence was similar to a strain in Minnesota, United States, which was the first ever isolated, with 85% nucleotide and 94% amino acid sequence similarities. Unlike the Minnesota strain, which lacks 220 nt including the 6K1 protein region, the Japanese isolate contains this coding region, which is commonly found in those of the Potyviridae.

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12.
Endophytic fungi were isolated from healthy stems and pods of cacao ( Theobroma cacao ) trees in natural forest ecosystems and agroecosystems in Latin America and West Africa. These fungi were collected for screening as a potential source of biocontrol agents for the basidiomycetous pathogens of cacao in South and Central America, Moniliophthora roreri (frosty pod rot) and Moniliophthora perniciosa (witches' broom). Many of these isolates were morphologically unidentifiable as they failed to form fruiting structures in culture, or only produced arthrosporic stages. Affinities with basidiomycetes were suspected for many of these based on colony morphology. Fifty-nine of these morphologically unidentifiable isolates were selected for molecular identification by DNA extraction and sequence analysis of nuclear ribosomal DNA (rDNA). The large subunit (LSU) was chosen for initial sequencing because this region has been used most often for molecular systematics of basidiomycete fungi, and comprehensive LSU datasets were already available for sequence analyses. Results confirmed that the majority of the isolates tested belonged to the Basidiomycota, particularly to corticoid and polyporoid taxa. With LSU data alone, identification of the isolates was resolved at varying taxonomic levels (all to order, most to family, and many to genus). Some of the isolates came from rarely isolated genera, such as Byssomerulius , whilst the most commonly isolated basidiomycetous endophyte was a member of the cosmopolitan genus Coprinellus (Agaricales). The role of these fungi within the host and their potential as biological control agents are discussed.  相似文献   

13.
Composed mostly of fungivorous species, the genus Aphelenchoides also comprises 14 plant-parasitic species. The most common and devastating, A. besseyi, A. fragariae, A. ritzemabosi and A. subtenuis have been reported on more than 900 plant species. The combination of low inter-specific and high intra-specific morphological variability makes morphology-based identification extremely difficult within this genus, and has led to molecular tools being employed to ensure accurate diagnoses. rDNA markers are widely used for the identification of nematodes while the Cytochrome Oxidase I gene (COI) remains relatively unexplored despite its role as the standard barcode for almost all animal groups. To explore its suitability as a diagnostic tool, we studied a fragment of the mtCOI region of the four main plant-parasitic Aphelenchoides within a phylogenetic framework. We generated 69 mtCOI and 123 rDNA sequences of diverse Aphelenchoides taxa; 67 belong to the main plant-parasitic species including the first mtCOI sequence of A. fragariae and the first mtCOI and 28S sequences of A. subtenuis. mtCOI had a similar success rate for PCR amplification. Phylogenetic trees based on the three studied markers are largely in agreement with one another, validating their use for Aphelenchoides diagnosis; additionally, we were able to locate several misidentified sequences of plant-parasitic Aphelenchoides in existing databases. The concatenated analysis from the three markers resulted in a more robust insight into the phylogeny and evolution of Aphelenchoides, revealing that plant-parasitism has evolved independently at least three times within this genus, presumably from fungal-feeding ancestors.  相似文献   

14.
Seeds of selected European and Japanese winter wheat cultivars were grown at two experimental sites in China, namely Yaan, Sichuan province (YA), and Yangzhou, Jiangsu province (YZ), where wheat yellow mosaic bymovirus (WYMV) was severe. There were some differential responses of the cultivars to the virus isolates present at the two sites. The complete nucleotide sequence of both RNAs of both virus isolates was determined. Their genome organization was identical to that reported for a Japanese isolate and the sizes were very similar. Nucleotide comparisons demonstrated that parts of the CI and NIa coding regions on RNA1 and the N-terminal part of the P2 coding region on RNA2 were particularly variable, while substantially conserved regions occurred in the 3' UTR of RNA2, the 7K, one part of the CI and parts of the NIb and coat protein. It seems unlikely that differences in the 7K and NIa-VPg proteins are responsible for virulence differences and the CI and NIb regions were considered the most promising for further study.  相似文献   

15.
ABSTRACT The complete nucleotide sequence of wheat streak mosaic virus (WSMV) has been determined based on complementary DNA clones derived from the 9,384-nucleotide (nt) RNA of the virus. The genome of WSMV has a 130-nt 5' leader and 149-nt 3'-untranslated region and is polyadenylated at the 3' end. WSMV RNA encodes a single polyprotein of 3,035 amino acid residues and has a deduced genome organization typical for a member of the family Potyviridae (5'-P1/HC-Pro/P3/6K1/CI/6K2/VPg-NIa/NIb/CP-3'). Because WSMV shares with ryegrass mosaic virus (RGMV) the biological property of transmission by eriophyid mites, WSMV has been assigned to the genus Rymovirus, of which RGMV is the type species. Phylogenetic analyses were conducted with complete polyprotein or NIb protein sequences of 11 members of the family Potyviridae, including viruses of monocots or dicots and viruses transmitted by aphids, whiteflies, and mites. WSMV and the monocot-infecting, mite-transmitted brome streak mosaic virus (BrSMV) are sister taxa and share a most recent common ancestor with the whitefly-transmitted sweet potato mild mottle virus, the type species of the proposed genus "Ipomovirus." In contrast, RGMV shares a most recent common ancestor with aphid-transmitted species of the genus Potyvirus. These results indicate that WSMV and BrSMV should be classified within a new genus of the family Potyviridae and should not be considered species of the genus Rymovirus.  相似文献   

16.
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17.
马铃薯Y 病毒贵州黔西烟草分离物P1 基因序列分析   总被引：1，自引：0，他引：1  
 Potato virus Y (PVY) is the type member of the genus Potyvirus and infects several important solanaceous crops, including tobacco. PVY is one of the most widespread and economically destructive viruses.The P1 region of PVY had been used to determine the diversity, evolution and the homology based on the
geographic location of the virus. The P1 region of PVY tobacco isolate from Qianxi in Guizhou Province was cloned and sequenced. Database searches and multiple sequence alignment showed subtle variation within the same strain, while apparent variation between O strain and the other three strains, N, NTN and N∶O. Moreover, variation in P1 region of Qianxi isolate derived from the gene mutation rather than the recombination among genomes. Phylogenic analysis revealed that the clustering only discriminated O strain from others. Consequently, sequence analysis in P1 region is unable to afford strain determination.  相似文献   

18.
ABSTRACT Most of the 3,000 named species in the genus Cercospora have no known sexual stage, although a Mycosphaerella teleomorph has been identified for a few. Mycosphaerella is an extremely large and important genus of plant pathogens, with more than 1,800 named species and at least 43 associated anamorph genera. The goal of this research was to perform a large-scale phylogenetic analysis to test hypotheses about the past evolutionary history of Cercospora and Mycosphaerella. Based on the phylogenetic analysis of internal transcribed spacer (ITS) sequence data (ITS1, 5.8S rRNA gene, ITS2), the genus Mycosphaerella is monophyletic. In contrast, many anamorph genera within Mycosphaerella were polyphyletic and were not useful for grouping species. One exception was Cercospora, which formed a highly supported monophyletic group. Most Cercospora species from cereal crops formed a subgroup within the main Cercospora cluster. Only species within the Cercospora cluster produced the toxin cercosporin, suggesting that the ability to produce this compound had a single evolutionary origin. Intraspecific variation for 25 taxa in the Mycosphaerella clade averaged 1.7 nucleotides (nts) in the ITS region. Thus, isolates with ITS sequences that differ by two or more nucleotides may be distinct species. ITS sequences of groups I and II of the gray leaf spot pathogen Cercospora zeae-maydis differed by 7 nts and clearly represent different species. There were 6.5 nt differences on average between the ITS sequences of the sorghum pathogen Cercospora sorghi and the maize pathogen Cercospora sorghi var. maydis, indicating that the latter is a separate species and not simply a variety of Cercospora sorghi. The large monophyletic Mycosphaerella cluster contained a number of anamorph genera with no known teleomorph associations. Therefore, the number of anamorph genera related to Mycosphaerella may be much larger than suspected previously.  相似文献   

19.
One of the greatest impediments to the study of Fusarium has been the incorrect and confused application of species names to toxigenic and pathogenic isolates, owing in large part to intrinsic limitations of morphological species recognition and its application. To address this problem, we have created FUSARIUM-ID v. 1.0, a publicly available database of partial translation elongation factor 1-alpha (TEF) DNA sequences, presently representing a selected sample of the diversity of the genus diversity, with excellent representation of Type-B trichothecene toxin producers, and the Gibberella fujikuroi, Fusarium oxysporum and F. solani species complexes. Users can generate sequences using primers that are conserved across the genus, and use the sequence as a query to BLAST the database, which can be accessed at http://fusarium.cbio.psu.edu, or in a phylogenetic analysis. Correct identification of a known species in these groups often can be performed using this gene region alone. This growing database will contain only vouchered sequences attached to publicly available cultures. In the future, FUSARIUM-ID will be expanded to include additional sequences, including multiple sequences from the same species, sequences from new and revised species, and information from additional genes.  相似文献   

20.
ABSTRACT Amplified restriction fragment length polymorphism (AFLP) was used to assess the levels of genomic variations among species and isolates of the genus Colletotrichum. Our objective was to characterize at the molecular level two alfalfa pathogens, isolates Arl-NW and 57RR, which are unusually aggressive to anthracnose-resistant alfalfa cultivars and whose taxa has been uncertain based on morphological criteria. The fingerprint patterns obtained were complex but did enable us to place these two isolates within the species C. trifolii and C. gloeosporioides, respectively. The diversity detected with AFLP among and within Colletotrichum species from alfalfa and other crops corroborated their published taxonomy based on morphology, ribosomal DNA sequence, and random amplified polymorphic DNA analyses. Similarity matrices generated with three primer pairs were highly correlated and, thus, were combined to determine the similarity among the fungal species and isolates that were analyzed. Analysis of the data generated with each of the primer pairs individually and application of either distance or parsimony methods supported the placement of these two isolates. The parsimony method of data analysis was more confirmatory in the placement of Phoma medicaginis as an out-group than the distance method, using either simple matching or Jaccard's coefficients to generate the similarity matrices. Our conclusion is that the AFLP technique will be useful for identification of individual isolates within complex genera such as Colletotrichum because of its ability to generate large numbers of polymorphisms and the consistency of polymerase chain reaction amplification.  相似文献   

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