Beet Virus Q Research Articles

RNAseq Analysis of Rhizomania-Infected Sugar Beet Provides the First Genome Sequence of Beet Necrotic Yellow Vein Virus from the USA and Identifies a Novel Alphanecrovirus and Putative Satellite Viruses.

“Rhizomania” of sugar beet is a soilborne disease complex comprised of beet necrotic yellow vein virus (BNYVV) and its plasmodiophorid vector, Polymyxa betae. Although BNYVV is considered the causal agent of rhizomania, additional viruses frequently accompany BNYVV in diseased roots. In an effort to better understand the virus cohort present in sugar beet roots exhibiting rhizomania disease symptoms, five independent RNA samples prepared from diseased beet seedlings reared in a greenhouse or from field-grown adult sugar beet plants and enriched for virus particles were subjected to RNAseq. In all but a healthy control sample, the technique was successful at identifying BNYVV and provided sequence reads of sufficient quantity and overlap to assemble > 98% of the published genome of the virus. Utilizing the derived consensus sequence of BNYVV, infectious RNA was produced from cDNA clones of RNAs 1 and 2. The approach also enabled the detection of beet soilborne mosaic virus (BSBMV), beet soilborne virus (BSBV), beet black scorch virus (BBSV), and beet virus Q (BVQ), with near-complete genome assembly afforded to BSBMV and BBSV. In one field sample, a novel virus sequence of 3682 nt was assembled with significant sequence similarity and open reading frame (ORF) organization to members within the subgenus Alphanecrovirus (genus Necrovirus; family Tombusviridae). Construction of a DNA clone based on this sequence led to the production of the novel RNA genome in vitro that was capable of inducing local lesion formation on leaves of Chenopodium quinoa. Additionally, two previously unreported satellite viruses were revealed in the study; one possessing weak similarity to satellite maize white line mosaic virus and a second possessing moderate similarity to satellite tobacco necrosis virus C. Taken together, the approach provides an efficient pipeline to characterize variation in the BNYVV genome and to document the presence of other viruses potentially associated with disease severity or the ability to overcome resistance genes used for sugar beet rhizomania disease management.

Detection and prevalence of viruses associated with sugarbeet in the Tadla region of Morocco

Fifty-five soil samples were collected from sugarbeet fields with rhizomania occurrence in the region of Tadla. BNYVV was ascertained by RT-PCR in 40 out of 55 fields surveyed and the positive samples were subsequently examined for the presence of the different pathotype of BNYVV. Using the same technique, a survey was simultaneously undertaken to identify the occurrence of other soil-borne viruses, which might frequently associate with BNYVV such as beet soilborne virus (BSBV), beet soilborne mosaic virus (BSBMV) and beet virus Q (BVQ). Results indicated that most samples were infected with A-type BNYVV, but only 9% of the samples were positive for B-type BNYVV. BNYVV (72.7%) was the most frequently detected, followed respectively by BSBV (36.36%) and BVQ (30.9%). However, P-type BNYVV was not detected at all. Our results also indicated the likely absence of BSBMV in the Tadla region. Surprisingly, among the 40 BNYVV-infected samples, 17 were also infected with BVQ and 20 with BSBV. In conclusion, BSBV occurred in triple infections with BNYVV and BVQ. In addition, there was only one sample revealed positive for both viruses BNYVV-B and BVQ and four samples for BSBV infection. Therefore, this study is the first investigation of BSBV and BVQ in fields-grown sugarbeet of Morocco.

DETECTION OF BEET SOIL-BORNE VIRUS AND BEET VIRUS Q IN SUGARBEET IN GREECE

Sugar beet plants with typical rhizomania symptoms were collected from the five major cultivation zones of Greece. The presence of Beet necrotic yellow vein virus (BNYVV), the primary causal agent of the disease, was ascertained by DAS-ELISA in 38 out of 40 fields surveyed and the positive samples were subsequently examined for the presence of other soil-borne viruses which are frequently associated with rhizomania, using a multiplex RT-PCR assay targeting BNYVV, Beet soilborne virus (BSBV) and Beet virus Q (BVQ). The occurrence of BSBV and BVQ was confirmed in 9 and 23 rhizomania- infected fields, respectively. In contrast to surveys conducted in other countries, the presence of BVQ prevailed throughout Greece in dual infections with BNYVV, whereas BSBV was restricted to rhizomaniainfected fields from only two sugarbeet cultivation areas. Nine of the samples tested were infected with all three viruses. BSBV was always found in triple infections. To our knowledge, this is the first report of BSBV and BVQ in Greece. The future assessment of the impact of each of these viruses on sugarbeet could prove significant for breeding objectives in terms of achieving a more durable resistance to the rhizomania syndrome.

OCCURRENCE OF SOIL-BORNE SUGAR BEET VIRUSES TRANSMITTED BY POLYMYXA BETAE NORTHERN AND CENTRAL TURKEY

A survey was conducted to determine the incidence of Beet necrotic yellow vein virus (BNYVV), Beet soilborne virus (BSBV) and Beet virus Q (BVQ) and their vector Polymyxa betae in sugar beet fields in central and northern Turkey. A total of 510 soil samples were collected in 2004 and 2005. Three detection techniques were used: ELISA for BNYVV and BSBV, RT-PCR for BVQ and direct staining of bait plant root tissues for P. betae cystosori. Bait plant tests and ELISA showed that 54.3% of the soils contained viruliferous P. betae cystosori. BSBV single infections were the most prevalent (23.7%) followed by double infection with BNYVV (23.1%), and single infection of BNYVV (7.5%). It was also found that 31.4% of the roots were infested with aviruliferous P. betae cystosori while 14.3% of the roots did not contain any cystosori. Forty five samples were selected on the basis of their geographical locations and tested for the presence of BVQ by RT-PCR. However, BVQ was not detected in any sugar beet samples tested.

The beet virus Q coat protein readthrough domain is longer than previously reported, with two transmembrane domains

Ten beet virus Q (BVQ) strains from six different countries were sequenced to characterize the readthrough (RT) domain of the coat protein (CP). The GenBank/EMBL/DDBJ accession numbers for the sequences reported in this paper are FM244643-FM244652. With three nucleotide additions of 5, 285 and 1 nt, the common RT of 76 kDa was found to be longer than the single reference available to date (35 kDa). It is hypothesized that multiple inoculation cycles on Chenopodium quinoa were responsible for these three deletions in the C-terminal part of the BVQ RNA-2 previously described. Two putative transmembrane domains, TM1 and TM2, were predicted in the consensus amino acid sequence of the ten BVQ strains, and the putative BVQ TM2 was aligned with that of potato mop-top virus.

Molecular characterization of three soil-borne sugar beet-infecting viruses based on the coat protein gene.

SUMMARY Sugar beet (Beta vulgaris L. ssp. vulgaris) hosts the soil-borne viruses Beet necrotic yellow vein virus (BNYVV), Beet soil-borne virus (BSBV), Beet soil-borne mosaic virus (BSBMV) and Beet virus Q (BVQ). Only a few isolates of these viruses have been characterized at the coat protein (CP) gene level. In this work, CP gene sequences were determined of three isolates each of BNYVV, BSBV and BVQ from different parts of Poland (Wielkopolska, Mazowsze and Dolny Slask). Phylogenetic analysis showed that Polish BNYVV isolates belong to the A and B type groups. The CP gene of the three BSBV isolates had 98-100% identity with comparable sequences available in GenBank. CP genes of the three BVQ isolates were almost identical to one another (9899%) and contained three additional nucleotides, resulting in a further amino acid residue (arginine) at position 86, as reported by Lennefors et al. (2005).

First report of Beet soil-borne virus on sugar beet in China

Beet soil-borne virus (BSBV) and Beet virus Q (BVQ) are two members of the genus Pomovirus that are transmitted by Polymyxa betae. BVQ and BSBV are commonly found in fields where Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania disease, is present (Henry & Jones, 1986; Koenig et al., 1998; Meunier et al., 2003). During the growing season of 2006, 26 roots of sugar beet exhibiting moderate to severe symptoms of rhizomania were collected from three fields located in Inner Mongolia and Xinjiang Provinces for a survey to determine whether BSBV and BVQ were present in China. Viral RNA was extracted from partially purified viruses of beet roots as described by Han et al. (2000) and tested by RT-PCR using three specific primer sets (BSBV: 5′-ATG GTT GAT CCG CGG TAT GAA G-3′ and 5′-CTA TTC AAC CCA GCG CAA ACC AAC-3′; BVQ: 5′-ATG GTT GAT CCA AGA TAT GAG C-3′ and 5′-CTA TGA GCC GGT CCA CTT CAA TCC-3′; and BNYVV: 5′-GCG GAT CCA TGT CGA GTG AA G GTA GA-3′ and 5′-CGA AGC TTG CTA TTG TCC GGG TGG-3′, based on Accession Nos NC003518, NC003511 and S71490 respectively) and designed to amplify coat protein genes for BSBV, BVQ and BNYVV respectively. Fifteen of the 26 beet samples gave positive reactions for BSBV, 21 for BNYVV and 14 for both BSBV and BNYVV. BVQ was not detected in any sugar beet sample tested. Subsequently, three RT-PCR products amplified in sugar beet samples collected from different locations with the primers specific to BSBV were cloned and sequenced (GenBank Accession Nos EF113300, EF210553 and EF210552). Sequence analysis revealed that these submitted sequences shared nucleotide identity of 98–99% with the German BSBV isolate (Accession No. NC003518). The partially purified viruses from infected sugar beet root were used for mechanical inoculation of Chenopodium quinoa and C. amaranticolor, and local lesions were observed on inoculated leaves. Furthermore, BSBV was also confirmed by RT-PCR (as described above) in the local lesions that appeared approximately 5 days after mechanical inoculation. Combined, the RT-PCR detection, nucleotide sequences and symptoms on inoculated host plants confirm the presence and first occurrence of BSBV in Inner Mongolia and Xinjiang. This work was partially supported by the National Natural Science Foundation of China (30471136 and 30671359).

SURVEYS OF BEET NECROTIC YELLOW VEIN VIRUS, BEET SOIL-BORNE VIRUS, BEET VIRUS Q AND POLYMYXA BETAE IN SUGAR BEET FIELDS IN IRAN

The main Iranian sugar beet (Beta vulgaris) growing areas were surveyed for the occurrence and incidence of Beet necrotic yellow vein virus (BNYVV), Beet soil-borne virus (BSBV) and Beet virus Q (BVQ). Root samples from 3,486 plants were collected from 184 commercial sugar beet fields of 14 provinces from randomly selected and symptomatic plants and analysed by tissue-blot immunoassay (TBIA). Serological diagnoses were confirmed by reverse transcription-polymerase chain reaction tests (RT-PCR) using specific primers. Based on TBIA data, BNYVV was prevalent (overall incidence of 52.4%), followed by BSBV (9.8%) and BVQ (1.4%). High levels of virus infections (more than 70%) were found in Ardabil, Esfahan, Fars, Khorasan and Zanjan provinces, whereas Khuzestan was apparently “virus-free”. The putative vector of the soil-borne viruses, Polymyxa betae, was also detected by RT-PCR in 179 fields surveyed.

First Report of Beet virus Q on Sugar Beet in Poland.

The objective of this work was to determine whether Beet virus Q (BVQ), a member of the genus Pomovirus, is present in Poland. BVQ, like Beet necrotic yellow vein virus (BNYVV), is transmitted by Polymyxa betae Keskin. Earlier, BVQ was described as the Wierthe serotype of Beet soilborne virus (BSBV). Now, on the basis of its genomic properties (2), BVQ is recognized as a distinct virus species. BVQ is often found in fields where BSBV and BNYVV are present (4). During the fall of 2005, five plants of a cultivar susceptible to rhizomania (cv. Alyssa) and five resistant to rhizomania (cv. Henrietta) were collected from a field in the Wielkopolska Region of Poland, where BSBV and BNYVV had been previously identified, and tested for BVQ (1). All samples were analyzed by a double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) with antiserum against BNYVV (Bio-Rad, Hercules, CA). Rhizomania was identified only in sugar beet samples of the susceptible variety. The same samples were then tested using a triple antibody sandwich (TAS)-ELISA with commercial antisera against BSBV/BVQ (As-0576.2) and BSBV (As-0576.1) (DSMZ, Braunschweig, Germany). Nine sugar beet plants gave positive reactions with antiserum against BSBV/BVQ and negative reactions with antiserum specific to BSBV. Total RNA extracted from roots of 10 beet samples was then tested using a multiplex reverse transcription-polymerase chain reaction (mRT-PCR) and specific primers designed to amplify a fragment of the RNA2 for BNYVV and BVQ (3). The primers specifically amplified fragments of 545 bp and 291 bp of the BNYVV and BVQ, respectively. BNYVV was detected in all five samples from susceptible sugar beet plants. The presence of BVQ was confirmed in nine of the sugar beer plants, and the RT-PCR products were sequenced. Sequence analysis of the 206-nt amplicon sequence of the Polish isolate of BVQ (GenBank Accession No. DQ309444) indicated 97% nucleotide and 94% amino acid sequence identity with the previously published sequence of BVQ (GenBank Accession No. AJ223596) (2). To my knowledge, this is the first report of the natural occurrence of BVQ on sugar beet in Poland. In Europe, it has been previously reported in Belgium, Bulgaria, France, Germany, Hungary, Italy, the Netherlands, Spain, and Sweden (3,4).

First Report of Beet virus Q in Spain.

Beet virus Q (BVQ) is a member of the genus Pomovirus that is transmitted by Polymyxa betae Keskin. Initially described as the Wierthe serotype of Beet soilborne virus (BSBV), BVQ is now considered a distinct virus species based on its genomic properties (1). BVQ is commonly found in fields where BSBV and the causal agent of rhizomania disease, Beet necrotic yellow vein virus (BNYVV), are also present. Simultaneous infection of sugar beet plants with multiple virus species could affect disease symptom expression (4). For this reason, the pathogenicity of BVQ and its role in the epidemiology of rhizomania disease remain a subject of study. During 2004, six soil samples were collected from different sites in the Castilla-La Mancha Region in Spain (Albacete and Ciudad Real provinces) where rhizomania symptoms were observed in BNYVV-tolerant sugar beet cultivars. Soil from the Hainaut Region of Belgium, infected with BNYVV, BSBV, and BVQ and supplied by Prof. C. Bragard (Unité de Phytopathologie, Université Catholique de Louvain, Belgium) was used as a positive control. Sugar beet plants (cv. Asso) were grown in the soil samples for 45 days at 24°C and then root tissue was harvested. All samples were analyzed using enzyme-linked immunosorbent assay (ELISA) with commercial BNYVV antiserum (BIOREBA AG, Reinach, Switzerland) and BSBV/BVQ antisera (IC10 and 6G2) supplied by R. Koenig (Federal Biological Research Centre for Agriculture and Forestry, Braunschweig, Germany). Total RNA extracted from sugar beet roots as previously described (3) was tested using reverse transcription-polymerase chain reaction (RT-PCR). Primers BVQ3F (5'-GTT TTC AAA CTT GCC ATC CT-3') and BVQ3R2 (5'-CCA CAA TGG GCC AAT AGA-3'), which amplify a 690-bp fragment of the triple gene block region of BVQ RNA 3, were designed based on the published sequence (GenBank Accession No. AJ223598). The presence of BSBV and BNYVV was assayed using RT-PCR with previously described primers (2,3). BVQ was detected from plants grown in soil collected from La Roda (Albacete) in Spain and from Hainaut in Belgium. The fragments amplified from Spanish sample with BVQ3F and BVQ3R2 (GenBank Accession No. AY849375) showed 95.9% nucleotide sequence identity with the previously published sequence of BVQ (1). The La Roda BVQ isolate was mechanically transmitted to Chenopodium quinoa from infected sugar beet root tissue. BVQ was detected using RT-PCR in local lesions that appeared approximately 5 days after inoculation and subsequently spread along veins. To our knowledge, this is the first report of BVQ in soil from Spain, although it has been previously reported in Belgium, Bulgaria, France, Germany, Hungary, and the Netherlands (2). BSBV and BNYVV (type A) were detected in all six Spanish samples, as well as in the Belgian soil.

First Report of Beet soilborne virus in Poland.

Beet necrotic yellow vein virus (BNYVV), the casual agent of rhizomania disease, was identified in sugar beet plants from several fields in the Wielkopolska Region of Poland (1). In greenhouse studies, sugar beets were grown in the soil from one of these fields to bait soilborne viruses. Of 200 sugar beet plants, three developed symptoms of vein clearing, vein banding, and mosaic. Crude sap from symptomatic plants was used for mechanical inoculation of various plants species. In Chenopodium quinoa, C. amaranticolor, and Tetragonia expansa only local lesions were observed. Electron microscope examination of negatively stained leaf-dip preparations from symptomatic sugar beet plants showed a mixture of rod-shape particles from 70 to 400 nm long. Using double-antibody sandwich enzyme-linked immunosorbent assay tests, two symptomatic sugar beet plants gave positive reactions with antiserum against BNYVV (Bio-Rad, Hercules, CA) and a third plant gave a positive reaction with antisera against BNYVV and Beet soilborne virus (BSBV). Total RNA was extracted from roots and leaves of the symptomatic plants and used in a multiplex reverse transcription-polymerase chain reaction (mRT-PCR) assay. Specific primers were designed to amplify a fragment of the RNA1 for BSBV and RNA2 for BNYVV and Beet virus Q (BVQ) (2). Two mRT-PCR products amplified with the primers specific to BNYVV and BSBV were obtained and sequenced. A 274-nt amplicon sequence (GenBank Accession No. DQ012156) had 98% nucleotide sequence identity with the German BNYVV isolate F75 (GenBank Accession No. AF19754) and a 376-nt amplicon sequence (GenBank Accession No. AY999690) had 98% nucleotide and 98% amino acid sequence identity with the German BSBV isolate (GenBank Accession No. Z97873). The Polish BSBV isolate had 88% nucleotide and 62% amino acid sequence identity with BVQ, another pomovirus (GenBank Accession No. AJ 223596 formerly known as serotype Wierthe of BSBV (2). In 2005, mRT-PCR was used on samples collected from two fields of the Wielkopolska Region. Of 15 tested sugar beet plants, 12 gave positive reactions with primers specific for BSBV and nine with primers specific to BNYVV. To our knowledge, this is first report of BSBV in Poland. In Europe, BSBV was previously reported in England, the Netherlands, Belgium, Sweden, Germany, France, and Finland (2,3).

First Report of Beet virus Q on Sugar Beet in Iran.

During the 2001 growing season, a survey was conducted to determine the incidence of Beet necrotic yellow vein virus (BNYVV), Beet soilborne virus (BSBV), and Beet virus Q (BVQ) in Iran. A total of 2,816 random and 76 samples with rhizomania were collected from 131 fields in the main sugar beet cultivation areas of 13 provinces in Iran. All samples were tested using a tissue-blot immunoassay (TBIA) with commercial BNYVV (As-0799.1/CG6-F4), BSBV (As-0576.1), and BSBV/BVQ (As-0576.2) antisera provided by S. Winter (DSMZ, Braunschweig, Germany). For randomly collected samples, the highest incidence of virus infection was found for BNYVV (52.3%), followed by BSBV (9.5%) and BVQ (1.5%). Co-infection of BNYVV with BSBV or BVQ was 6.6% and 0.9%, respectively. Infection with both BSBV and BVQ was found in 16 (0.6%) samples. In addition, 0.4% (12) of the samples was infected with all three viruses. Our results indicated the presence of BVQ in samples from 10 fields located in Azarbayejan-e-gharbi, Esfahan, Fars, Kermanshah, Khorasan, Lorestan, and Semnan provinces of Iran, with or without rhizomania-like symptoms. The presence of viruses was confirmed using reverse transcription-polymerase chain reaction (RT-PCR) of RNA from 81, 19, and 14 root samples with positive reaction in TBIA to BNYVV, BSBV, and BVQ, respectively, with previously described primers (3,4). The primers specifically amplified fragments of 501 bp, 602 bp, 399 bp, and 291 bp of the BNYVV RNAs 1 and 4, BSBV RNA-2, and BVQ RNA-1, respectively. Our results indicated that the samples tested were also positive using RT-PCR. The putative vector for BNYVV, BSBV, and BVQ, Polymyxa betae, was also detected in 161 samples (from 127 fields) by amplification of a 170-bp fragment of the P. betae repetitive EcoRI-like fragments using previously described primers (4). RT-PCR products from 72 BNYVV-positive sugar beet root samples from 58 fields that also gave positive reactions in TBIA were analyzed using single-strand conformation polymorphism (SSCP) as previously described with extracts from root beards of the susceptible sugar beet cvs. OPUS and IC1 grown in the soils infested with BNYVV types A and B (provided by A. Meunier, Unite de Phytopathologie-UCL-AGRO-BAPA, Louvain-la-Neuve, Belgium) as positive controls (3). The patterns obtained with SSCP were uniform and showed widespread occurrence of BNYVV type A in almost all provinces surveyed. The fragments obtained for BNYVV RNAs 1 and 4 of an isolate from Qazvin (BNQ1) were sequenced (GenBank Accession Nos. AY703452 and AY703455) and compared with other sequences available in GenBank using Clustal W, which revealed 99.3 and 99.6% identity with the Japanese S (D84410) and Italian type A (AF197552) isolates, respectively. The economic importance of BVQ and its interactions with other sugar beet soilborne viruses remains a matter of debate. BNYVV and BSBV have been previously reported from Iran (1,2). To our knowledge, this is the first report of the natural occurrence of BVQ in sugar beets in Iran.

First report of Beet virus Q in Belgium.

Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania disease on sugar beet, has been reported in Belgium for more than 16 years. Other soilborne viruses belonging to the genus Pomovirus, such as Beet soilborne virus (BSBV) (3) and Beet virus Q (BVQ) (1), are suspected pathogens of sugar beets grown in Belgium. During the 2000 growing season, more than 20 fields showing rhizomania-like and yellowing symptoms on sugar beet leaves were investigated for the presence of BVQ, BNYVV, and BSBV. All samples were checked by enzyme-linked immunosorbent assay (ELISA) using commercial BNYVV (Sanofi Diagnostics Pasteur, Marnes-La-Coquette, France) and BSBV/BVQ (DSMZ, Braunschweig, Germany - AS-0576 polyclonal, AS-0576/2 MAb) antisera. RNA was extracted from sugar beet rootlets using an RNeasy extraction kit (Qiagen, Hilden, Germany), before performing a reverse transcription-polymerase chain reaction (RT-PCR) using primers (5'-GCTGGAGTATATCACCGATGAC-3' and 5'-AAAATC TCGGATAGCATCCAAC-3') designed to specifically amplify a 510-bp region of BVQ RNA-1. The presence of BSBV and BNYVV was also checked by RT-PCR using previously described primers (1,2). The BVQ-derived PCR product was sequenced and proved to be more than 99% identical to the Wierthe BVQ isolate nucleotide sequence. Soil transmission of BVQ was demonstrated through a bioassay using soil dilutions with quartz and sugar beet cv. Cadyx as bait. After 6 weeks, BVQ was detected by RT-PCR in bait plants. The putative vector, Polymyxa betae, was identified by lactophenol-cotton blue staining of the roots followed by microscopic examination. BVQ produces irregularly shaped local lesions that appear ≈5 days after mechanical inoculation and tend to spread along veins. BVQ was detected in six fields located in the Polders Region and Brabant Province of Belgium. BVQ was always found in sugar beet samples coinfected with BNYVV and BSBV. The economic significance of BVQ and its interaction with other viruses is not known.

Genome properties of beet virus Q, a new furo-like virus from sugarbeet, determined from unpurified virus.

Based solely on the information that beet virus Q (BVQ) contains tubular particles, the entire nucleotide sequence of its tripartite genome was determined from unpurified virus in ca. 40 ml crude sap from locally infected Chenopodium quinoa. A starting sequence for RNA 1 was generated using primers corresponding to highly conserved helicase domains in the respective RNAs of furo-, pomo-, peclu-, hordei- and tobraviruses, and was extended by a walking random-primed cDNA approach. The similarity of the 3' ends of furoviral RNAs allowed starting sequences for BVQ RNAs 2 and 3 to be obtained once the 3' end of RNA 1 was known. BVQ RNA 1 encodes a protein with a methyltransferase-like, a variable and a helicase-like region, and for a readthrough protein which, in addition, contains an RNA-dependent RNA polymerase region. RNA 2 carries the coat protein gene, a coat protein read-through protein gene and two additional ORFs which may have arisen by deletions from an originally larger readthrough domain. RNA 3 carries a triple gene block resembling that of several other rod-shaped viruses. The 5' UTRs of the three RNAs have the potential to form a series of hairpins with C-A and C-C mismatches resembling those found in tymoviral RNAs. The 3' ends can be folded into tRNA-like structures which are preceded by a long hairpin-like structure and an upstream pseudoknot domain. BVQ belongs to the recently proposed genus Pomovirus; it shows evolutionary relationships to furoviruses in sensu stricto, peclu-, hordei-, tobra-, tymo-, tobamo-, carla- and potexviruses.