psorosis

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Citrus psorosis virus (CPsV), genus Ophiovirus, family Ophioviridae, is the causal agent of a serious disease affecting citrus trees in many countries. The viral genome consists of three ssRNAs of negative polarity. Post-transcriptional gene silencing (PTGS), a mechanism of plant defence against viruses, can be induced by transgenic expression of virus-derived sequences encoding hairpin RNAs. Since the production of transgenic citrus lines and their evaluation would take years, a herbaceous model plant, Nicotiana benthamiana, was used to test hairpin constructs...

Citrus psorosis ophiovirus (CPsV), is considered to be of the most serious and deter mental virus pathogen's citrus species trees in Egypt. CPsV-EG was isolated from infected citrus grapefruit (C. paradisi Macf.) at Agric. Res. Centre (ARC). The grapefruit which used for CPsV-EG isolate was found to be free from CTV, CEVd and Spiroplasma citri where as gave -ve results with DTBIA, tissue print hybridization and Diene's stain respectively. CPsV-EG was detected on the basis of biological indexing by graft inoculation which gave oak leaf pattern (OLP) on Dweet tangor and serological assay by DAS-ELISA using Mab specific CPsV...

Citrus psorosis is a serious viral disease affecting citrus trees in many countries. Its causal agent is Citrus psorosis virus (CPsV), the type member of genus Ophiovirus. CPsV infects most important citrus varieties, including oranges, mandarins and grapefruits, as well as hybrids and citrus relatives used as rootstocks. Certification programs have not been sufficient to control the disease and no sources of natural resistance have been found. Pathogen-derived resistance (PDR) can provide an efficient alternative to control viral diseases in their hosts...

Citrus psorosis virus (CPsV), the type species of genus Ophiovirus, has a segmented, negative-stranded RNA genome. We examined the population structure and genetic variation of CPsV in three coding regions located in RNAs 1, 2 and 3, analysing 22 isolates from Argentina, California, Florida, Italy and Spain. Most isolates contained a predominant sequence and some minor variants. Estimations of the genetic diversity and phylogenetic clustering of isolates disclosed two populations, one comprising isolates from Spain, Italy, Florida and California and the other including the Argentinean isolates...

Citrus Psorosis in Argentina is a serious disease. Citrus is produced in two regions located in the northeast (NE) and northwest (NW) area of the country. These two areas have different climates and soil types, and therefore different citrus species and varieties are cultivated. In the NE region, Psorosis is epidemic, and in the NW region, the disease was described on several occasions since 1938, but it is not observed commonly in the orchards. Recently, trees with symptoms of Psorosis were observed in the Tucumán and Salta Provinces located in the NW region...

A multiplex polymerase chain reaction (mPCR) assay was developed to detect six RNA and one DNA citrus virus: Citrus leaf rugose virus (CLRV), Citrus psorosis virus (CPsV), Citrus tatter leaf virus (CTLV), Citrus tristeza virus (CTV), Citrus variegation virus (CVV), Citrus yellow mosaic virus (CYMV), and Indian citrus ringspot virus (ICRSV) from citrus plants. These seven viruses are classified in six different virus genera. Degenerate primers were designed based on the respective virus isolate sequence data available from the GenBank and were used for reliable detection of the different viruses by simplex- and mPCR...

The complete genomic sequence (11278 nt) of Citrus psorosis virus (CPsV), isolate P-121 from Spain, was determined and compared with those from isolate CPV-4 and from other ophioviruses. The three RNAs of P-121 had similar size and identical organization as those of CPV-4. The 24K and the RdRp proteins were potentially encoded in the viral complementary (vc) strand of RNA 1, the 54K protein potentially encoded in vcRNA 2 and the coat protein encoded in vcRNA 3. These four proteins from P-121 and CPV-4 had 87, 92, 93 and 94% amino acid identity, respectively, but only 22, 38, 25 and 33% identity with their homologous proteins from Mirafiori lettuce big vein virus (MLBVV), the only other ophiovirus completely sequenced...

Variability of the Coat protein (CP) gene of Citrus psorosis virus (CPsV) was assessed serologically, and by sequence analyses of two genomic regions located in the 3' (region C) and 5' (region V) halves of the gene. Analysis of 53 psorosis field sources from Campania, Italy, with 23 monoclonal antibodies revealed nine serogroups and at least ten different epitopes. Sequence analysis of 19 of these sources showed limited nucleotide diversity of the CP gene in the population. Diversity was slightly higher in region V than in region C...

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Citrus psorosis virus (CPsV), the type member of genus Ophiovirus, has three genomic RNAs. Complete sequencing of CPsV RNA 1 revealed a size of 8184 nucleotides and Northern blot hybridization with chain specific probes showed that its non-coding strand is preferentially encapsidated. The complementary strand of RNA 1 contains two open reading frames (ORFs) separated by a 109-nt intergenic region, one located near the 5'-end potentially encoding a 24K protein of unknown function, and another of 280K containing the core polymerase motifs characteristic of viral RNA-dependent RNA polymerases (RdRp)...

A 4018 nucleotide sequence was obtained for RNA 1 of Ranunculus white mottle virus (RWMV), genus Ophiovirus, representing an incomplete ORF of 1339 aa. Amino acid sequence analysis revealed significant similarities with RNA polymerases of viruses in the family Rhabdoviridae and a conserved domain of 685 aa, corresponding to the RdRp domain of those in the order Mononegavirales. Phylogenetic analysis indicated that the genus Ophiovirus is not related to the genus Tenuivirus or the family Bunyaviridae, with which it has been linked, and probably deserves a special taxonomic position, within a new family...

The complete nucleotide sequence of an ophiovirus associated with lettuce big-vein disease has been elucidated. The genome consisted of four RNA molecules of approximately 7.8, 1.7, 1.5 and 1.4 kb. Virus particles were shown to contain nearly equimolar amounts of RNA molecules of both polarities. The 5'- and 3'-terminal ends of the RNA molecules are largely, but not perfectly, complementary to each other. The virus genome contains seven open reading frames. Database searches with the putative viral products revealed homologies with the RNA-dependent RNA polymerases of rhabdoviruses and Ranunculus white mottle virus, and the capsid protein of Citrus psorosis virus...

Citrus psorosis virus (CPsV) causes a citrus disease occurring worldwide. Isolate CPV 4 has a genome with three single-stranded RNAs. The complete sequence of RNA 2 (1643 nucleotides) is reported here. Northern blot hybridization with strand-specific probes showed that most of the encapsidated RNA 2 is of negative polarity, although a small amount of the complementary strand may also be present in particles. The RNA 2 complementary strand contained a single open reading frame encoding a protein of 476 amino acids, which includes a motif resembling a nuclear localization signal...

Several economically important diseases of unknown or recently determined cause are reviewed. Citrus blight (CB), first described over 100 years ago, was shown in 1984 to be transmitted by root-graft inoculations; the cause remains unknown and is controversial. Based on graft transmission, it is considered to be an infectious agent by some; others suggest that the cause of CB is abiotic. Citrus variegated chlorosis, although probably long present in Argentina, where it was considered to be a variant of CB, was identified as a specific disease and shown to be caused by a strain of Xylella fastidiosa after if reached epidemic levels in Brazil in 1987...

Psorosis is a widespread and damaging disease of citrus in many parts of the world. The causal agent is a multipartite virus with RNA genome present in very low concentration in infected citrus tissue. Diagnosis is made by biological indexing on indicator citrus seedlings, but it is a slow and costly procedure and therefore it is not used generally. No sensitive wide-spectrum assay for Citrus Psorosis virus (CPsV) has been reported based on RT-PCR. A highly sensitive heminested RT-PCR assay is described for the detection of CPsV...

An undescribed virus, here named ranunculus white mottle virus, was isolated in Italy from cultivated ranunculus showing mottle and distortion of leaves. The virus was mechanically transmissible to several herbaceous hosts. In negative stain, the particles appeared as circularised supercoiled threads 3 nm in diameter of different contour lengths; in some conditions the circles collapsed to form linear pseudobranched structures 9 nm in diameter. Immunolabeling of thin sections showed that viral antigen was widely distributed in the cytoplasm of parenchyma cells...

Citrus psorosis virus (CPV) is a multicomponent ssRNA virus with a coat protein of approximately 48 kDa. The viral genome is encapsidated in short and long particles that are readily separated by sucrose density-gradient centrifugation. CPV particles are spiral filaments that are referred to as spiroviruses (SV). A cDNA library of purified short particles from isolate CPV-4 was prepared in a Lambda vector and screened for expression of the coat protein gene (CPG) with a monoclonal antibody to the coat protein...

Some properties of the particles of citrus ringspot virus (CtRSV) and the related citrus psorosis-associated virus (CPsAV) are described. The particles of CtRSV have been reported to be sinuous linear structures about 10 nm in diameter and of two lengths (300 to 500 nm and 1500 to 2500 nm) representing 'top' and 'bottom' sedimentation components. We show that these particles are collapsed double-stranded forms of nucleocapsid-like, highly flexuous open circles formed of filaments 3 to 4 nm in diameter. Top-component filaments had contour lengths of 600 to 1000 nm, i...

Isolate 90-1-1 Concordia (Argentina) of the citrus psorosis agent was graft-transmitted to citrus and mechanically transmitted to Chenopodium quinoa, which was used as a local lesion assay host. Infected citrus and C. quinoa plant lesions were used as starting materials for the purification of the psorosis-associated agent. In extracts partially purified by differential centrifugation, infectivity was abolished by RNase treatment, even in 0.3 M NaCl, indicating that ssRNA is required for biological activity...