Parsnip Yellow Fleck Virus Research Articles

Parsnip yellow fleck virus

This datasheet on Parsnip yellow fleck virus covers Identity, Distribution, Hosts/Species Affected.

Virusi biljaka familije štitonoša

The Apiaceae are a large plant family consisting of approximately 250 genera and over 3,000 species grown worldwide. Its representative vegetables are carrot, parsley, parsnip and celery, as well as some wellknown spice plants such as fennel, anise, caraway, dill, and coriander. Their production is imperiled by numerous pathogens, among which viruses are of great importance. Globally more than 30 viruses are known to affect carrot and other plant species belonging to family Apiaceae. The principal viruses are: Celery mosaic virus (CeMV), Parsnip yellow fleck virus, (PYFV), Carrot red leaf virus (CtRLV) and Carrot mottle virus (CMoV). In Serbia, three viruses are present on carrot and celery: CeMV, Cucumber mosaic virus (CMV) and Tomato spotted wilt tospovirus (TSWV). The economic importance of viruses infecting umbelliferous has long been recognised due to the foliar symptoms and viral dieback of seedlings. These viruses affect carrot crops only sporadically, but when they do occur they can be devastating. Other umbelliferous viruses are known to occur worlwide, however, their effects are not clear.

Identification of a maize chlorotic dwarf virus silencing suppressor protein

Maize chlorotic dwarf virus (MCDV), a member of the genus Waikavirus, family Secoviridae, has a 11784 nt (+)ssRNA genome that encodes a 389kDa proteolytically processed polyprotein. We show that the N-terminal 78kDa polyprotein (R78) of MCDV acts as a suppressor of RNA silencing in a well-established assay system. We further demonstrate that R78 is cleaved by the viral 3C-like protease into 51 and 27kDa proteins (p51 and p27), and that p51 is responsible for silencing suppressor activity. Silencing suppressor activity of R78 is conserved in three divergent MCDV strains (MCDV-Severe, MCDV-M1, and MCDV-Tennessee), as well as the waikavirus Bellflower vein chlorosis virus, but was not detected for orthologous protein of Rice tungro spherical virus (RTSV-A) or the similarly-positioned protein from the sequivirus Parsnip yellow fleck virus (PYFV). This is the first identification of a virus suppressor of RNA silencing encoded by a waikavirus.

Carrot yellow leaf virus is associated with carrot internal necrosis.

Internal necrosis of carrot has been observed in UK carrots for at least 10 years, and has been anecdotally linked to virus infection. In the 2009 growing season some growers had up to 10% of yield with these symptoms. Traditional diagnostic methods are targeted towards specific pathogens. By using a metagenomic approach with high throughput sequencing technology, other, as yet unidentified causes of root necrosis were investigated. Additionally a statistical analysis has shown which viruses are most closely associated with disease symptoms. Carrot samples were collected from a crop exhibiting root necrosis (102 Affected: 99 Unaffected) and tested for the presence of the established carrot viruses: Carrot red leaf virus (CtRLV), Carrot mottle virus (CMoV), Carrot red leaf associated viral RNA (CtRLVaRNA) and Parsnip yellow fleck virus (PYFV). The presence of these viruses was not associated with symptomatic carrot roots either as single viruses or in combinations. A sub-sample of carrots of mixed symptom status was subjected to MiSeq sequencing. The results from these tests suggested Carrot yellow leaf virus (CYLV) was associated with symptomatic roots. Additionally a novel Torradovirus, a novel Closterovirus and two novel Betaflexiviradae related plant viruses were detected. A specific diagnostic test was designed for CYLV. Of the 102 affected carrots, 98% were positive for CYLV compared to 22% of the unaffected carrots. From these data we conclude that although we have yet to practically demonstrate a causal link, CYLV appears to be strongly associated with the presence of necrosis of carrots.

Complete nucleotide sequence of an isolate of the Anthriscus strain of Parsnip yellow fleck virus

Complete nucleotide sequence of an isolate of the Anthriscus strain of Parsnip yellow fleck virus

First Report of a Lettuce-Infecting Sequivirus in Chile.

Sequiviruses are isometric aphidborne plant viruses. Dandelion yellow mosaic virus (DaYMV), genus Sequivirus, was isolated from dandelion and lettuce in Europe. Lettuce mottle virus (LeMoV), a putative sequivirus, is often found in mixed infections with Lettuce mosaic virus (LMV) in Brazil (3). DaYMV, LeMoV and LMV cause similar mosaics in field-grown lettuce. Differences in biology and sequence suggest that DaYMV and LeMoV are distinct species (2). Forty-two and 101 lettuce samples with mosaic symptoms collected from two locations near Santiago during a survey of lettuce viruses in Chile in 2002 and 2003, respectively, were analyzed for the presence of LeMoV using reverse transcription polymerase chain reaction (RT-PCR). Total RNA was extracted (1) and used for RT-PCR with the specific LeMoV primers pairs Lmo3 (5' ACATGAGCACTAGTGAGG 3') and Lmo4 (5' AGATAGAGCCGTCT GGCG 3') (2). One of the 42 and three of the 101 samples produced the expected 300-bp fragment. Isometric particles of 30 nm diameter, typical of a sequivirus, were visualized by transmission electron microscopy. These samples were tested using RT-PCR for the presence of LMV and Cucumber mosaic virus (CMV), but no mixed infections were observed. One isolate, Ch36, was reamplified with the degenerate primer pairs DALE 1 (5' GARTTCAACATGCACGCCAG 3') and DALE 2 (5' TTTTTCTCCCCATYCGTCAT 3') which amplify part of the putative replicase gene (2) and produced a 563-bp fragment that was cloned on pGEM-T Easy (Promega, Madison, WI) and sequenced. The Ch36 product (EMBL Accession No. AM039965) showed 97% amino acid identity with LeMoV from Brazil, 79% with DaYMV, 72% with the sequivirus Parsnip yellow fleck virus, and 34% with the waikavirus Maize chlorotic dwarf virus. To our knowledge, this is the first report of a sequivirus in field lettuce in Chile, and although the virus was found at low incidence, this report extends the range of LeMoV to the western side of the Cordillera de Los Andes. The impact of LeMoV needs to be further analyzed in Chile, Brazil, and possibly other South American countries.

The nucleotide sequence of parsnip yellow fleck virus: a plant picorna-like virus.

The complete sequence of 9871 nucleotides (nts) of parsnip yellow fleck virus (PYFV; isolate P-121) was determined from cDNA clones and by direct sequencing of viral RNA. The RNA contains a large open reading frame between nts 279 and 9362 which encodes a polyprotein of 3027 amino acids with a calculated M(r) of 336212 (336K). A PYFV polyclonal antiserum reacted with the proteins expressed from phage carrying cDNA clones from the 5' half of the PYFV genome. Comparison of the polyprotein sequence of PYFV with other viral polyprotein sequences reveals similarities to the putative NTP-binding and RNA polymerase domains of cowpea mosaic comovirus, tomato black ring nepovirus and several animal picornaviruses. The 3' untranslated region of PYFV RNA is 509 nts long and does not have a poly(A) tail. The 3'-terminal 121 nts may form a stem-loop structure which resembles that formed in the genomic RNA of mosquito-borne flaviviruses.

Immunogold Localization of Parsnip Yellow Fleck Virus Particle Antigen in Thin Sections of Plant Cells

SUMMARY The distribution of parsnip yellow fleck virus particle antigen in infected cells of Nicotiana clevelandii or Spinacia oleracea was examined by immunogold labelling of ultrathin sections. Best results were obtained by pretreating sections with Decon 75 followed by long incubation times on antiserum (16 h) and gold probe (6 h). The cytoplasmic inclusions induced by infection have three main components: accumulations of 20 to 30 nm diameter tubules, granular bodies and amorphous matrix material. Much gold label was located over the areas of amorphous matrix material whereas the other components of the inclusions were not labelled. Specific but less dense labelling was observed over virus-induced cell wall outgrowths, and over other areas of cell wall and some nuclei in infected cells. Virus-like particles found in 45 nm diameter tubules within the cell wall outgrowths were not labelled, perhaps because they were inaccessible to the antibody. The results indicate that large amounts of virus particle antigen are present in cells. However, the number of recognizable virus particles was considerably less than expected from the amount of virus extracted from leaves.

Specificity of the effect of sap‐transmissible viruses in increasing the accumulation of luteoviruses in co‐infected plants

SummaryThe concentration of potato leafroll luteovirus (PLRV) (c. 1300 ng/g leaf) in singly infected Nicotiana clevelandii plants was increased up to 10‐fold in plants co‐infected with each of several potyviruses, or with narcissus mosaic potexvirus, carrot mottle virus or each of three tobravirus isolates. With the tobraviruses, PLRV concentration was increased equally by co‐infection with either NM‐type isolates (coat protein‐free cultures containing RNA‐1) or M‐type isolates (particle‐producing cultures containing RNA‐1 and RNA‐2). In contrast, the accumulation of PLRV was not substantially affected by co‐infection with either of two nepoviruses, cucumber mosaic cucumovirus, broad bean mottle bromovirus, alfalfa mosaic virus, pea enation mosaic virus or parsnip yellow fleck virus. The specificity of these interactions between PLRV and sap‐transmissible viruses was retained in tests made in Nicotiana benthamiana and when beet western yellows luteovirus was used instead of PLRV.

Particle properties of parsnip yellow fleck virus

SummaryParticle preparations of parsnip yellow fleck virus (PYFV) isolates A‐421 and P‐121, representing the two major serotypes, were made by clarifying leal extracts with ether or butan‐1‐ol and concentrating the virus particles by precipitation with polyethylene glycol and differential centrifugation. The preparations contained c. 31 nm‐diameter particles comprising two sedimenting components. Top component (T) consisted of stain‐penetrable protein shells with A260/A280= 0.8–0.9, sedimentation coefficient (S20) = 56 S (A‐421) or 60 S (P‐121), and buoyant density = 1.297 g/cm3. Bottom component (B) consisted of nucleoprotein particles, not penetrable by negative stain, with A260/A280= 1.9, sedimentation coefficient (S020.w) = 148 S (A‐421) or 153 S (P‐121), and buoyant density = 1.520 g/cm3 (A‐421) or 1.490 g/cm3 (P‐121). Yields of B component particles were up to c. 1 mg/100 g leaf tissue (both isolates); yields of T component particles were up to c. 0.6 mg (A‐421) or 5.5 mg (P‐121) per 100 g leaf tissue. PYFV particles were found to contain a single RNA species (mol. wt c. 3.4 × 106, c. 9800 nucleotides), constituting 40% of the particle weight, and three polypeptide species, of mol. wt (× 10 3)30, 26 and 24 (A‐421) or31, 26 and 23 (P‐121).

Host ranges and serological properties of eight isolates of parsnip yellow fleck virus belonging to the two major serotypes

SummaryIsolates of parsnip yellow fleck virus (PYFV) from parsnip (P‐121), celery (CV506 and CV065) and Heracleum sphondylium (Hs2) were serologically close to each other but distant from isolates from carrot (Dc2 and Dc5) and Anthriscus sylvestris (A‐421 and As2), which were in turn close to each other serologically. The two groups of isolates also differed from each other in host range. Minor differences in immunological reactions and in host range and symptomatology were observed between isolates in each group. Particles of all eight isolates had similar RNA and protein compositions. The data confirm that PYFV isolates fall into two major serotypes, those from parsnip, celery and H. sphondylium belonging to the P‐121 serotype and those from carrot and A. sylvestris belonging to the A‐421 serotype.

Virus infection and furanocoumarins in celery

Celery infected with celery mosaic virus or parsnip yellow fleck virus contained the furanocoumarins angelicin, bergapten, psoralen, trimethylpsoralen and xanthotoxin in concentrations from 0.3 to 3.6 μg/g fresh mass. They were not detected in celery plants grown in aseptic culture, and only occasionally found in apparently healthy plants in the glasshouse.

Is celery yellow net c used by parsnip yellow fleck virus

Celery yellow net w s described by Hollings (1964) s severe dise se of celery (Apium graveolens L. var. duke (Miller) DC.) that could be transmitted by grafting nd occasionally by mechanical inocul tion with leaf extracts. Pemberton & Frost (1986) observed similar symptoms in celery crops. but were unable to isolate the causal agent.During recent attempts to isolate the causal gent of celery yellow‐spot, another disease previously reported by Hollings (1964) and Pemberton & Frost (1986), we found that two of our samples from crop in Cheshire contained different virus. As well as yellow spots, these two plants also had yellow‐net symptoms on the older leaves, and one of the plants was stunted with some distortion of the young leaflets. The two virus isolates appeared identical from extensive testing on range of herbaceous indicator plants, so one of them, CV506, w s selected for further study

Viral dieback of carrot and other umbelliferae caused by the Anthriscus strain of parsnip yellow fleck virus, and its distinction from carrot motley dwarf

Viral dieback of carrot, chervil, coriander, dill and wild Umbelliferae is described. Disease incidence in carrot crops grown for seed is often high but low in ware carrot. There is no secondary spread in carrot crops.

Improved Estimates of Molecular Weight of Plant Virus RNA by Agarose Gel Electrophoresis and Electron Microscopy after Denaturation with Glyoxal

SUMMARY The RNA molecules of 13 plant viruses were denatured by heating at 50 °C in 1 m-glyoxal, 50% dimethyl sulphoxide, and their mol. wt. (expressed as the sodium salts) estimated both by electrophoresis in 0.75% agarose gel, and by measuring their lengths in the electron microscope. The two methods gave similar results. Compared with previous estimates obtained by electrophoresis at 60 °C in 2% polyacrylamide gels containing 8 m-urea, the new estimates were similar for molecules of mol. wt. up to about 1.7 × 106 (about 5000 nucleotides) but became increasingly larger as the mol. wt. exceeded this value. The mol. wt. of the RNA-1 molecules of a range of nepoviruses were all found to be about 2.7 × 106 to 2.8 × 106 (about 7800 to 8100 nucleotides) by the glyoxal/agarose method compared with about 2.1 × 106 to 2.2 × 106 (about 6100 to 6400 nucleotides) by the hot urea/polyacrylamide method. The estimated mol. wt. of RNA-1 (B-RNA) of cowpea mosaic virus (CPMV) was 2.39 × 106 (6900 nucleotides), about 20% greater than the commonly used value, those of the single RNA species of apple chlorotic leafspot and heracleum latent viruses were 2.48 × 106 (7170 nucleotides) and 2.52 × 106 (7260 nucleotides) respectively and that of parsnip yellow fleck virus was 3.34 × 106 (9650 nucleotides). Values of 2.37 × 106 (6840 nucleotides) and 0.54 × 106 (1550 nucleotides) were found respectively for RNA-1 and RNA-2 of the CAM strain of tobacco rattle virus (TRV). For the nepoviruses, and for CPMV and TRV, the new mol. wt. estimates were in good agreement with those predicted from the morphology or sedimentation behaviour of the virus particles. Electrophoresis of glyoxylated RNA in agarose gels is preferred to other electrophoretic methods for determining the mol. wt. of RNA molecules larger than about 1.7 × 106 (about 5000 nucleotides), and appears reliable for mol. wt. up to at least about 3.5 × 106 (10000 nucleotides).

Transmission and differentiation of six viruses infecting hogweed (Heracleum sphondylium) in Scotland

SUMMARYSix viruses, code‐named HV1‐HV6, were transmitted manually and/or by aphids (Cavariella spp. from symptomless wild plants of hogweed (Heracleum sphondylium) in Scotland. HV1 was identified as parsnip yellow fleck virus (PYFV); anthriscus yellows virus, on which it depends for transmission by aphids, was presumably also present in the hogweed plants. HV2 was transmitted manually and by aphids and had very flexuous filamentous particles c. 700–750 nm long; it has affinities with the closteroviruses, and the name heracleum latent virus is proposed. HV3, HV4 and HV5 were transmitted manually, HV3 and HV5 also by aphids, but their particle morphology is unknown. HV6 was transmitted only by aphids and has very flexuous particles up to 1400 nm long; it is presumably a closterovirus distinct from HV2. All the viruses infected cultivated umbelliferous species experimentally but only PYFV is known to infect umbelliferous crops.

Relations of carrot red leaf and carrot mottle viruses with their aphid vector, Cavariella aegopodii

SUMMARYStudies with Scottish isolates of carrot red leaf (CRLV) and carrot mottle (CMotV) viruses confirmed the dependency of CMotV on CRLV for transmission by the aphid Cavariella aegopodii. CMotV was transmitted by aphids only when the two viruses were present in the same source plant, and its transmission was not assisted by anthriscus yellows virus, which acts as a helper for parsnip yellow fleck virus. Some test plants became infected with CRLV alone, and a few with CMotV alone. In winter, aphid transmission of CRLV and CMotV was greatly increased when the source plants received supplementary lighting whereas the CMotV infectivity of sap was not increased.C. aegopodii acquired CRLV and CMotV after minimum acquisition access times of 30 min and inoculated them after minimum inoculation access times of 2 min. There was a minimum latent period of 7–18 h. The viruses were retained by the aphid after moulting and are therefore circulative in the vector, but were not transmitted to progeny insects. Aphids allowed 24 h to acquire the viruses continued to transmit them for at least 12 days, but some aphids allowed 6 h or less for virus acquisition ceased to transmit after 3 or 4 days. CRLV is considered a tentative member of the luteovirus group.

The role of the helper virus, anthriscus yellows, in the transmission of parsnip yellow fleck virus by the aphid Cavariella aegopodii

SUMMARYTransmission of parsnip yellow fleck virus (PYFV) by the aphid Cavariella aegopodii occurs only when the aphids are also carrying the helper virus, anthriscus yellows (AYV). None of five other viruses tested was able to act as helper. In experiments in which aphids were allowed to feed through membranes on crude or treated extracts from infected plants, aphids already carrying AYV acquired PYFV, but virus‐free aphids failed to acquire either AYV or PYFV. PYFV was not transmitted by insects injected with haemolymph from aphids carrying both viruses, or with purified preparations of PYFV. PYFV was transmitted when AYV‐carrying aphids, except those whose stylets had been removed, were contaminated externally with PYFV preparations.Ultraviolet irradiation of infected leaves did not prevent aphids from acquiring AYV, presumably because it is confined to deeply‐lying tissues. AYV‐carrying aphids could acquire PYFV from u.v.‐irradiated leaves after acquisition access times of 2 h but not after feeds of only 2 or 15 min (which are adequate on unirradiated leaves), suggesting that PYFV is present in all parts of the leaf. No ‘helper agent’ distinct from AYV itself was detected in these experiments or in experiments on minimum acquisition feeding time or maximum period of persistence in the aphid. U.v.‐inactivated PYFV competed with infective PYFV for retention sites in AYV‐carrying aphids, whereas AYV apparently did not. It is suggested that there is no helper agent for PYFV, other than AYV particles. The possibility that there is one for AYV is not excluded.

Relations of the semi‐persistent viruses, parsnip yellow fleck and anthriscus yellows, with their vector, Cav arietta aegopodii

SUMMARYStudies were made of the relations of parsnip yellow fleck virus (PYFV) and its helper virus, anthriscus yellows (AYV), with their aphid vector, Cavariella aegopodii. Apterous insects were more efficient vectors than alates; apterous nymphs were as efficient as apterous adults. C. aegopodii never transmitted PYFV in the absence of AYV, but aphids carrying both viruses infected some test plants with one or other virus alone. C. aegopodii that fed first on a source of AYV and then on a source of PYFV transmitted both viruses to test plants, but aphids that fed on the sources in the reverse order transmitted only AYV. Test plants receiving some aphids from a source of AYV, and others from a source of PYFV, became infected only with AYV. C. aegopodii acquired AYV or the AYV/PYFV complex from plants in a minimum acquisition access time (AAT) of 10–15 mm and inoculated the viruses to test plants in a minimum inoculation access time (IAT) of 2 min. Increasing either AAT or IAT, or both, to 1 h or longer increased the frequency of transmission of each virus. Starving the insects before the acquisition feed on AYV or AYV/PFYV sources did not affect transmission. Aphids already carrying AYV acquired PYFV from plants in a minimum AAT of only 2 min; they acquired and inoculated PYFV in a minimum total time of 12 min. The data suggest that AYV is confined to deeply lying tissues whereas PYFV is distributed throughout the leaf. C. aegopodii transmitted both PYFV and AYV in a semi‐persistent manner: the aphids retained both viruses for up to 4 days but lost them on moulting. Neither virus was passed to progeny of viruliferous adults. Earlier results suggesting that AYV is a persistent virus may have been caused by contamination of the AYV culture with carrot red leaf virus.

Association of Virus-like Particles with the Foregut of the Aphid Cavariella aegopodii Transmitting the Semi-persistent Viruses Anthriscus Yellows and Parsnip Yellow Fleck

SUMMARY The aphid Cavariella aegopodii transmits anthriscus yellows virus (AYV) and parsnip yellow fleck virus (PYFV) in a semi-persistent manner and loses them on moulting. It transmits PYFV only when it is also carrying AYV. The particles of AYV have not been seen in preparations or sections from infected plants but those of PYFV are isometric, about 30 nm in diam. in negative stain. Groups of a few to several hundred virus-like particles about 20 to 28 nm in diam. were seen by electron microscopy in the foregut of C. aegopodii transmitting AYV or the AYV/PYFV complex but not in aphids fed on healthy plants or on a source of PYFV alone. The particles were surrounded by densely staining material, which was in turn embedded in a matrix of lightly staining material (M-material), overlying a 15 to 20 µm-long portion of the intima lining the ventral wall of the pharynx (anterior portion of the foregut). In this region the intima is thickened and formed into several spike-like protrusions. The M-material also occurred in aphids fed on healthy plants, but less commonly than in those fed on infected plants. In some aphids that were fixed immediately after feeding on AYV-infected plants, additional groups of virus-like particles were found free in the foregut lumen. The particles in the matrix were not found until the aphids had fed on AYV-infected plants long enough to acquire transmissible virus, but they were still present in aphids that had fed for 2 h on 10% sucrose after feeding for 24 h on a source of AYV. In moulting aphids, the matrix, with associated virus-like particles, remained attached to the old pharynx lining. It is thought that the virus-like particles are those of AYV and that the matrix is the specific site of retention within the aphid. No differences were observed between aphids carrying AYV and those carrying both AYV and PYFV, and it is not known whether some of the particles found in insects carrying both viruses are those of PYFV.