Luteovirus Research Articles

First report of Turnip yellow virus (TuYV) in Brassica juncea (Indian mustard) in India

Figure 2 A survey for Turnip yellow virus (TuYV) was carried out during October-December 2012 covering the major field crops in Rajasthan, India. Fifty leaf samples with yellowing and red stripes were collected from Brassica juncea (Indian mustard) fields. The observed symptoms and the presence of a large number of aphids (Myzus persicea) indicated the presence of a virus, possibly TuYV. To confirm the presence of TuYV, total RNA was extracted from infected leaves using the TRIZOL plant mini kit (Invitrogen), according to the manufacturer’s protocol. RT-PCR was performed in a single PCR tube with the reaction mixture (20 μl) containing 10 ng RNA, 1 μl of 20 pmol oligo d(T), 1 μl of 20 pmol of Luteovirus group primers Lu1 and Lu4 (Robertson et al., 1991), 2 μl of 10x reaction buffer, 0.5 μl of 10 mM dNTPs, 0.5 μl of 50 mM MgCl2, 0.5 μl of AMV reverse transcriptase and 0.5 μl of Taq polymerase (3U/μl). The RT-PCR was performed in a thermal cycler with the following programme: reverse transcription at 42°C for 1 hour, initial denaturation at 94°C for 2 min, followed by 35 cycles of 94°C for 30 sec, annealing at 50°C for 1 min, extension at 72°C for 1 min and a final extension of 72°C for 10 min. An amplicon of expected size (~600 nt) (Fig. 1) was sequenced and submitted to GenBank (Accession No. KC570457, isolate RP1). BLAST analysis of the nucleotide sequence showed 91-97% identity with the corresponding region of TuYV (X13063), Beet western yellows virus (BWYV; L40015, Y11531) and TuYV isolate WA-1 (JQ862472.1).

Towards universal detection of <i>Luteoviridae</i>

Luteoviridae is a plant virus family of 26 species which causes yield losses in cereals potatoes and other economically important crops worldwide Accurate detection is an important component of controlling the spread of luteoviruses and reducing yield losses PCRbased detection is often the method of choice for Luteoviridae as it is more sensitive than serological methods which frequently fail to detect infection due to the low concentration of luteoviruses in plants Since the currently available luteovirus primers are mostly speciesspecific and work under different PCR conditions universal primers are desirable Seven primers were tested that were designed to target the most conserved regions of the Luteoviridae genomes and that possess high homology to over 75 of Luteoviridae species Thirty luteovirus isolates representing 15 species were obtained from New Zealand and overseas these included all five species from the Luteovirus genus eight of the nine species from the Polerovirus genus (except CYDV RPS) PEMV1 (the only species from the Enamovirus genus) and CtRLV (which is not assigned to a genus) Between them the three combinations of primers detected all 13 of the Luteovirus and Polerovirus species tested

Occurrence and distribution of sugar beet viruses in Lebanon

Field surveys were carried out in the main sugar beet growing areas of Lebanon to assess the occurrence and distribution of viral diseases. A total of 1002 samples from 115 commercial fields were serologically assessed for Beet Necrotic Yellow Vein Furovirus (BNYVV), Beet Yellows Closterovirus (BYV), Beet Mosaic Potyvirus (BtMV), Beet Western Yellow Luteovirus (BWYV) and Cucumber Mosaic Cucumovirus (CMV). ELISA tests revealed that 39.5% of samples were infected with one or more viruses. BtMV was the most common (56.5%), followed by BYV (29.5%), BNYVV (17%) and BWYV (11%). Mixed infections were detected in 5.2% of the samples. CMV was not encountered. Direct tissue printing of plants infected with BtMV, BYV and BWYV on a nitrocellulose membrane gave very strong positive reactions.

Survey of Faba Bean ("Vicia faba" L.) Virus Diseases in Ethiopia

Surveys conducted in 1996 and 1997 to assess the status of virus diseases affecting faba bean in the major growing areas of Ethiopia indicated that leaf yellowing, rolling, necrosis and stunting were the most common disease symptoms. The highest visually-observed disease incidence in a field was 85%, recorded in the Wello region (north-eastern Ethiopia). When 3049 symptomatic samples collected from 211 fields from all over Ethiopia were tested by the tissue blot immunoassay (TBIA) for 14 viruses, 1592 samples (52.2%) were found to be infected with at least one virus. Faba bean necrotic yellows virus (FBNYV, genus Nanovirus) was the most frequent (63.2%), followed by luteoviruses (28.5%) [such as Beet western yellows virus (BWYV, genus Polerovirus, family Luteoviridae) and Bean leaf roll virus (BLRV, family Luteoviridae)] and Chickpea chlorotic dwarf virus (CCDV, genus Mastrevirus, family Geminiviridae) (3.1%). Mosaic/mottling symptoms were observed in some fields but incidence was always very low (<1%). The mosaic/mottling causing viruses identified were Broad bean stain virus (BBSV) and Broad bean true mosaic virus (BBTMV) (genus Comovirus, family Comoviridae), Pea seed-borne mosaic virus (PSbMV) and Bean yellow mosaic virus (BYMV) (genus Potyvirus, family Potyviridae). Testing of 3035 random samples collected in 1997 from 37 fields in the Shewa and Arsi regions revealed 1.6% luteovirus and 0.6% FBNYV infection, indicating that the incidence of these viruses on faba bean is very low in central Ethiopia. The survey suggested that virus diseases are currently of economic importance on faba bean in north-eastern Ethiopia and potentially important in the other areas, with FBNYV and luteoviruses being the most important.

Sources of Resistance to Cucurbit Aphid-borne Yellows Luteovirus in a Melon Germ Plasm Collection

Dogimont, C., Slama, S., Martin, J., Lecoq, H., and Pitrat, M. 1996. Sources of resistance to cucurbit aphid-borne yellows luteovirus in a melon germ plasm collection. Plant Dis. 80:13791382. Cucurbit aphid-borne yellows virus (CABYV) is a tentative member of the luteovirus group transmitted by Myzus persicae and Aphis gossypii. Five hundred twenty-three Cucumis melo L. accessions were screened in field conditions in the south of France under severe natural inoculum pressure. Double antibody sandwich-enzyme-linked immunosorbent assays were conducted to confirm the presence or absence of virus in the plants. Several potential sources of CABYV resistance were found, most originating from India, but some from Korea and Africa. The resistance of the most promising genotypes was confirmed in a field trial in five locations and under controlled conditions, with viruliferous Myzus persicae used to inoculate plants. Genotypes found to be resistant were Faizabadi Phoont, 90625, PI 124112, PI 124440, PI 255478, PI 282448, and PI 414723.

Pepper Vein Yellows Virus, a Novel Luteovirus from Bell Pepper Plants in Japan.

Bell pepper plants showing vein yellowing and leaf roll symptoms were observed in plastic houses at Kitanakagusuku, Okinawa Prefecture in 1981. The causal agent did not infect plants by mechanical inoculation or through seed but was transmitted by grafting and two species of aphids, Aphis gossypii Glover. collected from pepper and Myzus persicae Sulz. in a persistent manner. The causal agent has limited host range, only infect Capsicum species. In serological tests this agent did not react with antisera to potato leaf roll virus, tobacco necrotic dwarf virus, barley yellow dwarf virus and beet western yellows virus. Partially purified preparations contained spherical particles 25nm in diameter. In ultrathin sections virus-like particles were observed only in the phloem cells of infected pepper plants. Based on these results the causal agent was classified as a new member of the luteovirus group and named pepper vein yellows virus (PeVYV).

Increase in Cucurbit Aphid–Borne Yellows Virus Concentration by Co–infection with Sap–transmissible Viruses does not Increase its Aphid Transmissibility

AbstractThe cucurbit aphid–borne yellows virus (CABYV) is a new tentative member of the luteovirus group which is transmitted persistently by Myzus persicae and Aphis gossypii.In muskmelon plants, mixed infection with CABYV and zucchini yellow mosaic virus (ZYMV) induced an increase in CABYV concentration estimated by double antibody sandwich–enzyme linked immunosorbent assay (DAS–ELISA), which was maximum after 3 weeks, of co–infection.Assays, conducted with other cucurbit hosts and sap–transmissible viruses showed that a similar increase occurred with most of the potyviruses tested. However, cucumber mosaic virus (CMV) and squash mosaic virus (SqMV) were inefficient for less efficient than potyviruses) in increasing CABYV concentration.Aphid transmission experiments were conducted to check whether increased virus multiplication could either enhance transmission rates or modify the mode of CABYV acquisition by aphids. However, when A. gossypii was used, no increases in CABYV, transmissibility nor in its acquisition mode were detected.

Assessment of the autonomy of replicative and structural functions encoded by the luteo-phase of pea enation mosaic virus.

The genome of pea enation mosaic virus (PEMV) is composed of two taxonomically unrelated RNAs, interacting to create what has traditionally been considered a bipartite virus. The cohesiveness of this interaction was assessed by examining the autonomy of each RNA in viral replication, coat protein expression and systemic invasion. Using a pea protoplast system, in vitro transcripts of RNA1 were found to be capable of initiating RNA2-independent replication, including the formation of the distinctive nuclear membrane-based replication complex associated with wild-type PEMV infection. Western blotting and electron microscopic analysis demonstrated that the synthesis of the RNA1-encoded coat protein, as well as virion assembly, was also independent of RNA2-directed functions. Mechanical inoculations with transcripts of RNA1 failed to establish a systemic RNA1 infection, whereas inoculations with RNA2 were able to establish a largely asymptomatic systemic infection. Combined inoculum containing RNA1 and RNA2 transcripts were able to recreate wild-type PEMV symptomatology, demonstrating the dependence of RNA1 on RNA2 for mechanical passage. With the notable exception of the adaptation of PEMV to establish a true systemic invasion, these data further strengthen the analogy between PEMV and the helper-dependent complexes associated with members of the luteovirus group.

Soybean Dwarf Luteovirus Contains the Third Variant Genome Type in the Luteovirus Group

Complementary DNAs covering the entire RNA genome of soybean dwarf luteovirus (SDV) were cloned and sequenced. Computer analysis of the 5861 nucleotide sequence revealed five major open reading frames (ORFs) possessing conservation of sequence and organisation with known luteovirus sequences. Comparative analyses of the genome structure show that SDV shares sequence homology and features of gene organisation with barley yellow dwarf virus (PAV isolate) in the 5′ half of the genome, yet is more closely related to potato leafroll virus in its 3′ coding regions. In addition, SDV differs from other known luteoviruses in possessing an exceptionally long 3′ terminal sequence with no apparent coding capacity. We conclude from these data that the SDV genome represents a third variant genome type in the luteovirus group.

The chimeric nature of the genome of pea enation mosaic virus: the independent replication of RNA 2.

The genome of pea enation mosaic virus (PEMV) consists of two plus-sense RNAs, both of which are required for mechanical transmission. RNA 1 (5706 nucleotides) has strong sequence similarity with members of the luteovirus group, a similarity that is also manifested in the symptomatology, cytopathology and vector transmission of this virus. RNA 2 (4253 nucleotides) is hypothesized to facilitate systemic invasion and mechanical transmission, attributes that distinguish PEMV from the phloem-limited luteoviruses. Sequence analysis of RNA 2 has demonstrated that PEMV is unique among multicomponent viruses in that it lacks 3'- and 5'-terminal homology between its genomic RNAs. Sequence analysis of RNA 2 has identified an open reading frame encoding a putative product of 65K that contains a series of polymerase-like motifs typical of viral RNA-dependent RNA polymerases. This protein sequence lacks homology with the polymerase encoded on RNA 1 of PEMV, instead being more closely affiliated with the polymerases of viruses related to the carmo- and tombusvirus groups. Inoculation of pea protoplasts with RNA transcripts derived from a full-length cDNA clone of RNA 2 has demonstrated that RNA 2 replicates autonomously in the absence of RNA 1, although comparable inoculation of whole plants failed to establish a systemic infection. There is no evidence that RNA 2 encodes structural proteins, suggesting that encapsidation functions are supplied in trans by RNA 1, comparable to the helper-dependent complexes occurring within the luteovirus group. These data suggest that the PEMV genome can be characterized as a symbiotic association of two taxonomically distinct viral RNAs cooperatively interacting in the establishment of a systemic virus infection.

A new yellowing disease of cucurbits caused by a luteovirus, cucurbit aphid‐borne yellows virus

Since 1988, a yellowing disease of melon, cucumber and zucchini squash has been frequently observed in summer and autumn crops in France. Infected plants show yellowing and thickening of the older leaves; symptom intensity differs depending upon cultivar and season, and can be easily overlooked when plants are already infected by mosaic‐inducing viruses or other pathogens. The disease is associated with the presence of a virus with spherical particles c. 25 nm in diameter, which is readily transmitted in a persistent manner by the aphids Myzus persicae and Aphis gossypii, but not mechanically. Serological analysis, nucleic‐acid‐hybridization experiments and host‐range studies indicate that the virus is distantly related to, but distinct from, beet western yellows virus (BWYV). We propose to name this virus cucurbit aphid‐borne yellows virus (CABYV), and to consider it as a tentative new member of the luteovirus group. CABYV was found to reduce significantly the yields of melon and cucumber by decreasing the number of fruit per plant but not by altering the fruit shape or quality. Preliminary investigations of the epidemiology of CABYV indicate that the virus is common in weeds and in cultivated cucurbits. CABYV was frequently detected in various regions of France, suggesting that it is one of the most prevalent viruses infecting cucurbits in this country.

Inheritance of Resistance to Beet Western Yellows Virus in Lactuca virosa L.

Beet western yellows virus (BWYV), a member of the Luteovirus group, causes severe losses in many lettuce-growing areas. Attempts to identify complete resistance to BWYV in lettuce cultivars (Lactuca sativa L.) or in L. serriola L. and L. saligna L. were unsuccessful. Among three accessions of L. virosa tested, one, IVT 280, appeared to be extremely resistant to BWYV. Heredity of this resistance was studied in crosses with susceptible L. virosa IVT 1398. The results were compatible with the hypothesis of one gene, with resistance being dominant. The symbol Bw for Beet western is proposed for this gene.

Retrospective estimation of the data of infection with beet yellowing viruses in sugar-beet under field conditions

Sugar-beet plants, infected with beet yellows virus (BYV, closterovirus group) or beet mild yellowing virus (BMYV, luteovirus group) develop symptoms on the inoculated leaves on which aphids infected the plant. Symptoms develop also on the systemically-infected leaves to which virus has been transported via the phloem. Systemic infection occurs in the leaves which have just, or not yet appeared at the moment of infection of the plant. All other, older leaves remain uninfected. The infection-date can be estimated by assessing the date of appearance of the oldest systemicallyinfected leaf of a plant. This approach was tested in the field and gave good results.

Distribution, host range and some properties of a virus disease of sunflower in Kenya

Abstract Apparently similar viruses were associated with two different disease symptoms in sunflower (Helianthus annuus) in Kenya, one a yellow blotch and the other a leaf crinkle. The virus occurred in all sunflower‐growing regions but the crinkle disease was confined to areas east of the rift valley. Disease incidence varied with locality and season. Mechanical transmission of virus from plants with either disease was possible, but the yellow blotch virus was also transmissible from an important alternate field host, Tridax procumbens by Aphis gossypii to 23 species in three families. Partially purified preparations of virus made from mechanically inoculated seedlings affected with either symptom type contained 26 nm virus particles which, in ISEM tests, reacted with antisera prepared against six members of the luteovirus group.

Serotype-specific and General Luteovirus Probes from Cloned cDNA Sequences of Barley Yellow Dwarf Virus

Summary Genome fragments from two serotypes of barley yellow dwarf virus (BYDV) were cloned and used as hybridization probes. Dot blot assays using 32P-labelled plasmid probes readily detected BYDV in crude sap extracts from infected plants and were at least as sensitive as ELISA. Some clones were specific for either the RPV or the PAV serotypes. Others hybridized not only with the RNA of both serotypes but also with those of three other luteoviruses (beet western yellows, potato leaf roll and soybean dwarf), but they did not hybridize with the RNA of a tobamovirus or Escherichia coli tRNA. These nucleic acid probes therefore have potential for the general diagnosis of infection by members of the luteovirus group as well as detection of specific BYDV serotype infections. The taxonomic implications of the observation that the genomes of different luteoviruses have some conserved regions are discused.

Carrot Red Leaf and Carrot Mottle Viruses: Observations on the Composition of the Particles in Single and Mixed Infections

SUMMARY Particles of carrot red leaf virus (CRLV; luteovirus group) purified from chervil (Anthriscus cerefolium) contain a single ssRNA species of mol. wt. about 1.8 × 106 and a major protein of mol. wt. about 25000. CRLV acts as a helper for aphid transmission of carrot mottle virus (CMotV; ungrouped) from mixedly infected plants. Virus preparations purified from such plants possess the infectivity of both viruses but contain particles indistinguishable from those of CRLV; some of the particles are therefore thought to consist of CMotV RNA packaged in CRLV coat protein. When RNA from such preparations was electrophoresed in agarose/polyacrylamide gels, CMotV infectivity was associated with an RNA band that migrated ahead of the CRLV RNA band and had an estimated mol. wt. of about 1.5 × 106, similar to that previously found for the infective ssRNA extracted directly from Nicotiana clevelandii leaves infected with CMotV alone. Preparations of dsRNA from CMotV-infected N. clevelandii leaves contained two species: one of mol. wt. about 3.2 × 106, presumably the replicative form of the infective ssRNA, and the other, mol. wt. about 0.9 × 106, of unknown origin and function. The infective agent in buffer extracts of CMotV-infected N. clevelandii was resistant to RNase (although the enzyme acted as a reversible inhibitor of infection at high concentrations) and is therefore not unprotected RNA. It may be protected within the approximately 52 nm enveloped structures previously reported.

Detection of a Luteovirus in Groundnut Rosette Diseased Groundnuts (Arachis hypogaea) by Enzyme‐linked Immunosorbent Assay and Immunoelectron Microscopy

AbstractIn groundnut rosette diseased groundnut plants collected near Zaria, Nigeria, a luteovirus was detected by ELISA and ISEM. In ELISA only beet western yellows virus antiserum reacted, while in ISEM luteovirus particles were trapped by antisera beet western yellows virus, potato leafroll virus, pea leafroll virus and barley yellow dwarf virus. The data are in agreement with the interpretation that the assistor of groundnut rosette virus is possibly a member of the luteovirus group.

Purification of a Tasmanian isolate of subterranean clover red leaf virus, and its serological interactions with a New Zealand isolate and other luteoviruses

A Tasmanian isolate of subterranean clover red leaf virus (SCRLV) was purified and concentrated from pea (Pisum sativunz L. cv. Puget) by tissue extraction with cellulase followed by heat clarification, precipitation with polyethylene glycol in salt, and differential and density gradient centrifugation. Virus particles were isometric and 27 nm in diameter. Aulacorthum solani (Kalt.) acquired virus particles from the preparations through Parafilm membranes and transmitted them to healthy subterreanean clover test seedlings, causing disease symptoms of SCRLV. Isolates of SCRLV from Tasmania appeared identical with those from New Zealand on the basis of particle morphology and serological tests. Tasmanian SCRLV was distantly related serologically to Californian isolates of beet western yellows (BWYV) and legume yellows (LYV) viruses. Tests indicated that the relationship was closest with a potato isolate of BWYV and most distant with LYV. Virus particles in sap extracts from infected pea plants were readily detected by electron microscopy following adsorption onto grids coated with SCRLV antiserum, but not on grids coated with antisera to BWYV and LYV. These data confirm that SCRLV is a new, distinct member of the luteovirus group.

Luteovirus-like Particles Associated with Subterranean Clover Red Leaf Virus Infection

SUMMARY Small isometric virus-like particles have been detected in thin sections of phloem transfer cells of subterranean clover plants infected with subterranean clover red leaf virus (SCRLV). Virus-like particles similar in size and appearance but serologically distinct from those of potato leafroll virus, were also detected in purified preparations from SCRLV-infected plants. The morphology of the particles and their distribution in infected cells is consistent with SCRLV being a member of the luteovirus group, as previously suggested by its biological properties.

Purification of carrot red leaf virus and evidence from four serological tests for its relationship to luteoviruses

SUMMARYCarrot red leaf virus (CRLV) was purified from infected chervil by centrifuging whole plant extracts at low speed and incubating the resuspended pellets with Driselase; the digest was then treated with 1% (v/v) Triton X‐100 and the virus concentrated by centrifugation twice at high speed through a layer of 20% sucrose. The preparations (about 1 μg virus/g tissue) contained isometric particles c. 25 nm in diameter which formed a single u.v.‐absorbing component in sucrose density gradients. Chervil seedlings exposed to aphids (Cavariella aegopodii) that had been injected with or had fed on fractions from the u.v.‐absorbing zone developed typical symptoms of infection with CRLV. CRLV particles had a sedimentation coefficient (s20,w) of 104 S, buoyant density in CsCl of 1.403 g/cm3 and A260/A280 of 1.62. Antiserum with a gel‐diffusion titre of 1/512 was obtained from a rabbit injected intradermally with 100 μg purified virus. CRLV was detected by immunosorbent electron microscopy and enzyme‐linked immunosorbent assay in extracts of the petioles and leaf midribs of infected chervil and in groups of five to 20 viruliferous C. aegopodii.Analysis of antiserum/virus reactions by density gradient centrifugation showed that CRLV is distantly related to all luteoviruses tested; its relationships were closest to barley yellow dwarf virus (RPV strain), and perhaps also to beet western yellows virus, more distant to tobacco necrotic dwarf, potato leafroll and bean leafroll viruses, and very distant to barley yellow dwarf (MAV strain) and soybean dwarf viruses. Some of these relationships were detected by double diffusion in agarose gels and by electron microscopy of antiserum/virus mixtures. Immunosorbent electron microscopy detected all these relationships but suggested that CRLV was more closely related to tobacco necrotic dwarf and potato leafroll viruses than to barley yellow dwarf virus (RPV strain).The results show that CRLV should be considered a definitive member of the luteovirus group, and provide confirmation of recent evidence that potato leafroll virus is a luteovirus.