Tobacco rattle virus genome alterations in the Hosta hybrid 'Green Fountain' and other plants: reassortments, recombinations and deletions.

Tobacco rattle virus from a Hosta hybrid contained one RNA1 (Ho-1) and two RNA2 species (Ho-2a, Ho-2b). Whereas Ho-1 resembles TRV Al RNA1 from Alstroemerias, Ho-2a and Ho-2b resemble TRV TpO1 RNA2 from a potato field. Ho-2a has a complete RNA2-specific sequence, whereas that of Ho2-b carries a large deletion. The short RNA1-related 3' end of Ho-2a is distinct from that of Ho-1, whereas the longer one of Ho-2b is identical to that of Ho-1. TRV RNA2 molecules may apparently become associated with different TRV RNA1 molecules, from which they can acquire 3'ends of various lengths while often losing large portions of their RNA2-specific sequences.

Deletions and recombinations with the RNA1 3' ends of different tobraviruses have created a multitude of tobacco rattle virus TCM-related RNA2 species in Alstroemeria and tulip.

In vegetatively propagated Alstroemeria plants that showed pronounced stunting and necrotic leaf spots, a tobravirus infection was diagnosed in which one tobacco rattle virus (TRV, strain AL) RNA1 species was associated with seven different RNA2 species. The latter differed considerably in size and in the types of their 3' RNA1-related sequences. The 5' RNA2-specific part of all these RNA2 molecules showed almost 100% sequence identity with that of RNA2 of the TRV isolate TCM from tulip, but in some of these RNA2 molecules it was shorter than in the TCM isolate, whereas in others it was longer. One of the TRV AL RNA2 molecules, i.e. TC3'PE-a, contained the full set of three full-length RNA2-specific ORFs (ORF2a, -2b and -2c), whereas the previously analysed TCM sequence contained only ORF2a and -2b. In four of these TRV AL RNA2 molecules, i.e. those that had a relatively short RNA2-specific part, the 3' end was identical to that of the cognate TRV AL RNA1, but in the other three, which had a long RNA2-specific part, it was closely related to that of pea early browning virus (PEBV) RNA1, which was not detected in the infected plants. A comparison with previously described TRV/PEBV RNA2 recombinants suggested that the various TRV AL RNA2 molecules may represent various steps and side steps in an evolutionary process, which is apt to open the wide host range of TRV also to PEBV-derived RNA2 species.

Host Range, Purification, and Genetic Variability in Sweet potato chlorotic fleck virus.

Sweet potato chlorotic fleck virus (SPCFV) has recently been classified as a putative new member of the genus Carlavirus (family Flexiviridae) on the basis of its molecular properties. In this study, SPCFV was characterized in terms of host range, physical and biological characteristics, and genetic variability. In addition to sweet potato, SPCFV infected some plant species in the families Convolvulaceae, Chenopodiaceae, and Solanaceae. Limited numbers of virus particles were observed in the assimilation parenchyma cells of infected plant tissues; some cells had a distorted and enlarged endoplasmic reticulum though without any cytoplasmic and amorphous inclusions. The normal length of SPCFV particles was determined to be approximately 800 nm. In enzyme-linked immunosorbent assays, polyclonal antibodies raised against purified SPCFV virions were able to detect the virus in infected sweet potato and indicator plant tissues. In immunoelectron microscopy, SPCFV particles were all strongly decorated when reacted with homologous antiserum. Comparison of the 3' terminal part of the genome of a range of geographically diverse isolates revealed a high level of genetic diversity. The amino acid sequence identity in the coat protein and the nucleic acid binding protein ranged from 89 to 99.7% and from 75.9 to 99.2%, respectively. Phylogenetic analysis of both proteins showed a geographically associated clustering into two genogroups.

Daphne decline: what is the causal agent(s)?

A double infection of Daphne mosaic virus (DapMV) and an associated bacilliform virus was observed in the samples of diseased Daphne mezereum shrubs that showed mosaic patterns, precocious leaves reddening, defoliation, repeated flowering with subsequent declining. Extensive aggregations of bacilliform particles (166-370 x 65 nm and 169-233 x 68-78 nm) occurred in the nucleus or perinuclear space of root and leaf tissues suggesting that the virus might belong to the genus Nucleorhabdovirus, family Rhabdoviridae. However, the single bacilliform virions appeared occasionally in the cytoplasm of the leaf cells. We supposed that occurrence of the mixed virus infection could be the cause of D. mezereum decline in the Czech Republic.

Zygocactus virus X-based expression vectors and formation of rod-shaped virus-like particles in plants by the expressed coat proteins of Beet necrotic yellow vein virus and Soil-borne cereal mosaic virus.

Expression vectors were constructed from 35S promoter-containing full-length cDNA clones of Zygocactus virus X (ZVX). The expression of foreign genes was driven by the ZVX coat protein (cp) subgenomic promoter. It was successful only when the variable region downstream of the conserved putative promoter region GSTTAAGTT(X(12-13))GAA was retained. Most of the ZVX cp gene, except for a short 3' part, was replaced by the corresponding sequence of the related Schlumbergera virus X (SVX) and its cp subgenomic promoter to enable encapsidation of the transcribed RNA by an SVX/ZVX hybrid cp. Vector-expressed cp of Beet necrotic yellow vein virus (BNYVV) assembled in Chenopodium quinoa, Tetragonia expansa and Beta vulgaris leaves into particles resembling true BNYVV particles. The virus produced from these constructs retained its ability to express BNYVV cp in local infections during successive passages on C. quinoa. This ability was lost, however, in the rarely occurring systemic infections.

Daphne mosaic virus (DapMV), a new potyvirus from Daphne mezereum in the Czech Republic.

Daphne shrubs with light green rings and mosaic on leaves contained flexuous filamentous virions (696 x 13 nm) and cylindrical inclusions typical of the subdivision III of Edwardson's classification for inclusions induced by members of the family Potyviridae. Decoration tests using antisera to 67 potyviruses revealed distant serological relations among chilli veinal mottle virus, Colombian datura virus, papaya ringspot virus, tobacco vein mottling virus and yam mosaic virus. The 3' terminal region of the virus genome was amplified by RT-PCR using primers specific for cloned and sequenced members of the family Potyviridae. The most similar sequences in the GenBank were those of isolates of wild potato mosaic virus (WPMV) and yam mild mosaic virus (YMMV), originating from Peru and Guadeloupe, respectively. The new sequence had 63.2% and 61.9% nucleotide identity to WPMV and YMMV in the coat protein gene. The results suggest that the Czech isolate from daphne should be regarded as a new member of the genus Potyvirus. The name daphne mosaic virus (DapMV) is suggested for this virus.

The phylogenetic structure of the cluster of tobamovirus species serologically related to ribgrass mosaic virus (RMV) and the sequence of streptocarpus flower break virus (SFBV).

Ribgrass mosaic virus (RMV), turnip vein-clearing virus (TVCV) and Youcai mosaic virus (YoMV; formerly designated as oilseed rape mosaic virus; ORMV) belong to the genus Tobamovirus and are arranged in one out of three subgroups because of their common host range, serological cross-reactivity and amino acid composition of their coat proteins. The recently defined species Wasabi mottle virus (WMoV) is closely related to the same subgroup. The distinction of the four species is difficult and the lack of sequence information of a wide range of isolates has led to an unclear nomenclature. To clarify this situation we sequenced the coat protein genes from 18 isolates which were serologically related to members of the species of this cluster. The size of the coat protein was conserved with the exception of one isolate which revealed an N-terminal extension due to the mutation of three stop-codons. Phylogenetic analysis of these CP ORFs resulted in a tree with three clusters each containing at least one of the approved species RMV, TVCV and 1ptYoMV/WMoV in which our isolates were distributed. The tree was congruent and did support the present taxonomic status of species within this subgroup. For practical purpose we developed a subgroup 3 specific primer pair and a species differentiating restriction fragment length polymorphism (RFLP). Sequencing of the genome of Streptocarpus flower break virus (SFBV) which is serologically distantly related to the subgroup 3 viruses revealed a distinct genome organization. Therefore we propose that this virus should be regarded as a member of a species not belonging to any of the subgroups so far established.

Chickpea chlorotic stunt virus: A New Polerovirus Infecting Cool-Season Food Legumes in Ethiopia.

ABSTRACT Serological analysis of diseased chickpea and faba bean plantings with yellowing and stunting symptoms suggested the occurrence of an unknown or uncommon member of the family Luteoviridae in Ethiopia. Degenerate primers were used for reverse transcriptase-polymerase chain reaction amplification of the viral coat protein (CP) coding region from both chickpea and faba bean samples. Cloning and sequencing of the amplicons yielded nearly identical (96%) nucleotide sequences of a previously unrecognized species of the family Luteoviridae, with a CP amino acid sequence most closely related (identity of approximately 78%) to that of Groundnut rosette assistor virus. The complete genome (5,900 nts) of a faba bean isolate comprised six major open reading frames characteristic of polero-viruses. Of the four aphid species tested, only Aphis craccivora transmitted the virus in a persistent manner. The host range of the virus was confined to a few species of the family Fabaceae. A rabbit antiserum raised against virion preparations cross-reacted unexpectedly with Beet western yellows virus-like viruses. This necessitated the production of murine monoclonal antibodies which, in combination with the polyclonal antiserum, permitted both sensitive and specific detection of the virus in field samples by triple-antibody sandwich, enzyme-linked immunosorbent assay. Because of the characteristic field and greenhouse symptoms in chickpea, the name Chickpea chlorotic stunt virus is proposed for this new member of the genus Polerovirus (family Luteoviridae).

Molecular characterization of isolates of anagyris vein yellowing virus, plantago mottle virus and scrophularia mottle virus -- comparison of various approaches for tymovirus classification.

The complete nucleotide sequences were determined for the genomic RNAs of three tymoviruses, i.e. isolates of anagyris vein yellowing virus (AVYV), plantago mottle virus (PlMoV) and scrophularia mottle virus (SrMV) which are all serologically closely related to ononis yellow mosaic virus (ibid) and to Nemesia ring necrosis virus (NeRNV), a recently described recombinant virus which is widely spread in commercially grown ornamental plant species belonging to the Scrophulariaceae. Total nucleotide and coat protein amino acid sequence identities revealed similar groupings in the genus tymovirus as serological studies did. The latter, however, tended to suggest much closer relationships than the molecular data and may fail to recognise the distinctiveness of new tymovirus species. The usefulness of various species demarcation criteria for the classification of tymoviruses is discussed.

Nemesia ring necrosis virus: a new tymovirus with a genomic RNA having a histidylatable tobamovirus-like 3' end.

The complete nucleotide sequence of the genomic RNA of the new virus Nemesia ring necrosis virus (NeRNV), which is widespread in various ornamental plant species belonging to the Scrophulariaceae and Verbenaceae, has been determined. Based on its gene content, the folding properties of its 5'-untranslated region and in vitro translation experiments, NeRNV RNA is a typical tymovirus RNA. Its 3' end, however, differs greatly from those of the valine-specific tymoviral RNAs that have been analysed previously. It can be folded into an upstream pseudoknot domain and a histidine-specific tRNA-like structure, a combination that, so far, has been found only in tobamoviral RNAs. The identity elements found in NeRNV RNA for recognition by yeast histidyl-tRNA synthetase are more similar to those of yeast tRNAHis than the ones found in tobacco mosaic virus RNA. As a result NeRNV RNA can be charged with histidine even more efficiently than tobacco mosaic virus RNA.

Localization of Poa semilatent virus cysteine-rich protein in peroxisomes is dispensable for its ability to suppress RNA silencing.

Subcellular localization of the Poa semilatent virus cysteine-rich gammab protein was studied by using different approaches. In infected tissue, gammab was detected mainly in the P30 fraction as monomers, dimers and oligomers. Green fluorescent protein-fused gammab was found to localize in punctate bodies in the cytoplasm. Colocalization with marker proteins demonstrated that these bodies represent peroxisomes. Immunoelectron microscopy revealed that gammab was localized in the peroxisomal matrix and that localization of gammab in peroxisomes required the C-terminal signal tripeptide SKL. An SKL-deletion mutant exhibited a diffuse localization, but retained the protein's ability to suppress RNA silencing, determine infection phenotype and support virus systemic spread. These data indicate that gammab functions are not associated with the protein's localization to peroxisomes.

Evaluation of various species demarcation criteria in attempts to classify ten new tombusvirus isolates.

The usefulness of various suggested species demarcation criteria was compared in attempts to determine the taxonomic status of ten new tombusvirus isolates. Five of them (Lim 1, 2, 3, 5 and 6) were obtained from different sources of commercially grown statice (Limonium sinuatum), two (Gyp 1 and 2) from different sources of commercially grown Gypsophila paniculata and three from water samples, i.e. from a small river (Schunter) in Northern Germany, from a brook (near Dossenheim) in Southern Germany and from the groundwater in a Limonium production glasshouse in the Netherlands (Lim 4). The immunoelectron microscopical decoration test allowed a quick preliminary assignment of various isolates to several known tombusviruses. A more precise analysis of the relationships was achieved by comparing the deduced amino acid sequences of the coat proteins. Sequence as well as serological data suggested that eight of the isolates should be classified as strains or variants of either Carnation Italian ringspot virus, Grapevine Algerian latent virus, Petunia asteroid mosaic virus or Sikte waterborne virus, respectively, whereas the 9th isolate (Lim 2) appears to represent a distinct new tombusvirus species. The case of the 10th isolate (Lim 5) illustrates the classification problems experienced when the properties of a virus place it close to the more or less arbitrary man-made borderline between virus species and virus strains. The coat protein gene sequences were also determined for some viruses for which these data had not yet been available, i.e. Neckar river virus, Sikte waterborne virus and Eggplant mottled crinkle virus. The sequences of the coat protein gene and also of ORF 1 of the latter virus proved to be almost identical to the corresponding genome regions of the recently described Pear latent virus, which for priority reasons should be renamed. Criteria which have been suggested in addition to serology and sequence comparisons for tombusvirus species demarcation, i.e. differences in natural and in experimental host ranges, in cytopathological features and in coat protein size, appear to be of little value for the classification of new tombusviruses.

Pelargonium necrotic spot virus: a new member of the genus Tombusvirus.

A virus isolate from Pelargonium spp., provisionally designated UPEV (unknown pelargonium virus), had isometric particles 31-33 nm in diameter, with a granular surface structure similar to that of viruses in three genera of family Tombusviridae. Immunoelectron microscopy proved that UPEV was serologically distinct from all examined morphologically similar members of the family Tombusviridae. The induced cytopathology was characterized by large cytoplasmic virion aggregates and the formation of multivesicular bodies derived from mitochondria. Analysis of the complete ssRNA genome sequence revealed four open reading frames (ORFs) arranged like those of viruses in the genera Tombusvirus and Aureusvirus. Sequence comparisons indicated that three of the four ORFs had a high identity (52-97% identical amino acids) with the respective ORFs of tombusvirus species, especially with Carnation Italian ringspot virus, but not with those of viruses in other genera in Tombusviridae. On the contrary, UPEV coat protein had a low indentity (36-53% identical amino acids) with that of the aureusvirus Pothos latent virus. The data suggested that UPEV originated in a recombination event between a tombus- and an aureusvirus. According to its original host and symptom expression we proposed the new virus be named Pelargonium necrotic spot virus (PeNSV) and classified it as a distinct and new species in the genus Tombusvirus.

Further characterization of 'sweet potato virus 2': a distinct species of the genus Potyvirus.

An incompletely described potyvirus isolate from sweet potato in Taiwan, referred to as 'sweet potato virus 2' (SPV2), was further characterised. Electron microscopy revealed that SPV2 has filamentous particles of 850 nm in length and induces cytoplasmic cylindrical inclusions consisting of pinwheels and scrolls. The virus was mechanically transmitted to several species of the genera Chenopodium, Datura, Nicotiana, and Ipomoea. Two biotypes of Myzus persicae transmitted SPV2 in a non-persistent manner. Decoration titer experiments revealed a distant serological relationship between SPV2 and other potyviruses infecting sweet potato. The 3'-terminal 2006 nucleotides of the viral RNA were determined and shown to be a potyviral genome fragment comprising the coding region for the C-terminal half of the NIb protein, the entire coat protein cistron, and the 3' untranslated region (UTR). Comparison of the capsid protein and 3' UTR sequences of SPV2 with those of other potyviruses demonstrated that it is a distinct member of the genus Potyvirus (family Potyviridae). We propose that SPV2 is named Sweet potato virus Y.

First Report of Chickpea Chlorotic Dwarf Virus Infecting Spring Chickpea in Syria.

During May 2003, a high incidence of symptoms suggestive of virus infection in spring chickpea were observed in many fields in Al-Ghab Valley, Syria, the ICARDA farm (near Aleppo, Syria), as well as in other locations in northern Syria, including the Idleb governorate. Symptoms observed were yellowing, stunting, and necrosis. A total of 1,345 chickpea samples with these symptoms (331 from Al-Ghab Valley, 269 from the ICARDA farm, and 745 from the Idleb governorate) were collected and tested for the presence of five viruses with tissue-blot immunoassay (TBIA) (4) at the Virology Laboratory of ICARDA, using the following antisera: monoclonal antibodies for Faba bean necrotic yellows virus (FBNYV, genus Nanovirus) (1); Bean leafroll virus (BLRV, family Luteoviridae) (4B10) (3); Beet western yellows virus (BWYV, genus Polerovirus, family Luteoviridae [ATCC PVAS-647, American Type Culture Collection, Manassas, VA]); and Soybean dwarf virus (SbDV, family Luteoviridae, [ATCC PVAS-650]) and polyclonal antibodies for Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus, family Geminiviridae, provided by H. J. Vetten, BBA, Braunschweig, Germany). The most common virus present was BWYV (detected in 54.1% of samples tested), followed by CpCDV (19.2%), BLRV (10.2%), and FBNYV (5.5%). SbDV was not detected in any of the samples tested. Using immunosorbent electron microscopy, infected chickpea samples revealed low numbers of geminivirus-like particles after 15 min of incubation on CpCDV antiserum-coated grids. When CpCDV was purified from infected chickpea plants, the virus coat protein was 32 kDa with sodium dodecyl sulfate-polyacrylamide gel electrophoresis typical of CpCDV coat protein (2) and reacted strongly with CpCDV antiserum in western blots. The CpCDV vector in Syria was found to be Orosius albicinctus Distant, and is thought to be similar to Orosius orientalis (Matsumura), the reported vector of CpCDV (2). FBNYV, BWYV, and BLRV infection of chickpea have been previously reported from Syria, but to our knowledge, this is the first report of CpCDV infecting chickpea in Syria. References: (1) A. Franz et al. Ann. Appl. Biol. 128:255, 1996. (2) N. M. Horn et al. Ann. Appl. Biol. 122:467, 1993. (3) L. Katul. Characterization by serology and molecular biology of bean leaf roll virus and faba bean necrotic yellows virus. Ph.D. thesis. University of Gottingen, Germany, 1992. (4) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994.

Molecular and serological relationships of Spartina mottle virus (SpMV) strains from Spartina spec. and from Cynodon dactylon to other members of the Potyviridae.

Spartina mottle virus (SpMV) was first reported 1980 and classified by physical and biological properties as a tentative member of the genus Rymovirus in the Potyviridae. This genus was recently separated into two genera: Rymovirus and Tritimovirus. Now the sequence of the 3'-terminal part of the genome of SpMV was determined. Additionally a virus isolate originating from Cynodon dactylon in Italy was cloned and sequenced. This Assisi-isolate shared 87.5% amino acid sequence identity with SpMV. The high degree of identity and their close serological relationship indicate that SpMV and Assisi-isolate have to be regarded as different strains of one virus. The Assisi-isolate should be designated as SpMV-AV. Comparing the C-terminal part of the ORF of several Potyviridae the sequences of SpMV strains were more similar to those of the genera Rymovirus and Potyvirus than to the genera Tritimovirus, Macluravirus, Bymovirus and Ipomovirus. The comparisons revealed identities of less than 32% for the CP and 37% for the 3'-NIb/CP region, indicating that SpMV can not be classified to any of the established genera. The results of serological tests support a separate position of SpMV in the Potyviridae. We propose to introduce the name Sparmovirus for the new genus.

Occurrence of Lily mottle virus in Escarole.

Lily mottle virus (LMoV), genus Potyvirus, an important virus of lily that also causes flower-breaking in tulip (1), is considered to have a natural host range restricted to the family Liliaceae. In 1996, escarole (Cichorium endivia L. var. latifolium LAM) plants growing in fields close to Torino, Italy, and showing mosaic and necrotic spots on outer leaves were infected by a potyvirus related to LMoV. The virus was identified by immunoelectron microscopy (IEM) done on experimentally infected Nicotiana benthamiana and Chenopodium quinoa. The virus isolated from escarole (LMoV-E) had an experimental host range similar to that of lily isolates of LMoV, although species within the Liliaceae were not tested. LMoV-E systemically infected all nine escarole cultivars and six of seven endive cultivars (C. endivia L. var. crispum LAM) but did not infect any of six lettuce and two chicory cultivars (C. intybus L. var. foliosum HEGI). Symptoms ranged from mild to severe mosaic and were generally more severe on escarole than on endive. Some of the same escarole, endive, and lettuce cultivars were inoculated with a typical LMoV isolate from lily (Le97/49, from A. F. L. M. Derks, the Netherlands), which induced mild systemic infections in only one escarole and one endive cultivar. Both cultivars were also susceptible to LMoV-E. LMoV-E was purified from N. benthamiana, and an antiserum was prepared. IEM decoration titer experiments were done with LMoV-E and four other LMoV isolates from Liliaceae and their homologous antisera. Heterologous titers ranging from identity to serological differentiation index values of 2 to 4 were obtained, confirming the identity of the escarole isolate as a LMoV strain and indicating considerable serological variability among LMoV isolates. In a field survey of endive and escarole crops in 1998, in the area where LMoV-E was first identified, the virus was again detected by enzyme-linked immunosorbent assay in 4 of 80 escarole plants tested. LMoV-E appears to be a LMoV strain particularly adapted to escarole. To our knowledge, this is the first report of LMoV identified in a naturally infected host outside monocotyledonous plants. Reference: (1) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993.

First Record of Pea enation mosaic virus Naturally Infecting Chickpea and Grasspea Crops in Syria.

Virus-like symptoms not commonly encountered on most chickpea (Cicer arietinum L.) and grasspea (Lathyrus sativus L.) genotypes were noticed at the ICARDA farm near Aleppo, Syria, during April and May 2001. Primary symptoms included stunting, accompanied by leaf mottling and yellowing. The causal agent was transmitted by the pea aphid (Acyrthosiphon pisum Harris) in a persistent manner. Efficiency of transmission was 100% when aphids acquired the virus from grasspea and then inoculated lentil, whereas transmission efficiency was 21% when aphids acquired the virus from chickpea and then inoculated lentil. Samples of symptomatic chickpea and grasspea reacted strongly with the antiserum prepared against a Dutch isolate (E154) of Pea enation mosaic virus (PEMV), provided by L. Bos (Wageningen, the Netherlands) (1), using tissue blot immunoassay (2). Negatively stained preparations from chickpea and grasspea revealed typical PEMV-like isometric particles ≍30 nm in diameter. With immunoelectron microscopy, these particles were effectively trapped and strongly decorated with PEMV antibodies (immunoglobulin G diluted 1:10) provided by M. Musil (Bratislava, formerly Czechoslovakia) (4). The virus capsid protein was 22 kDa based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, typical of the PEMV coat protein, and reacted strongly with PEMV antiserum (E154) in western blots. This is the first report of PEMV naturally infecting chickpea and grasspea in Syria and, to our knowledge, the first report in West Asia. PEMV reached epidemic levels on lentil in Syria for the first time in 1994 (3). Field symptoms observed in May 2001 suggest that PEMV may also seriously affect lentil, chickpea, and grasspea crops in Syria. References: (1) K. Mahmood and D. Peters. Neth. J. Plant Pathol. 79:138, 1973. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994. (3) K. M. Makkouk et al. Plant Dis. 83:303, 1999. (4) M. Musil et al. Acta Virol. 14:285, 1970.

First Report of Pepino Mosaic Virus on Tomato.

Early in 1999 a new viral disease occurred in protected tomato (Lycopersicon esculentum) crops in the Netherlands. Infected plants showed yellow leaf spots and mosaic. Transmission electron microscopic analysis revealed particles typical of potexviruses. Only three potexviruses have been reported to infect solanaceous crops: Pepino mosaic virus (PepMV), Potato aucuba mosaic virus (PAMV), and Potato virus X (PVX). Inoculation of test plants and serological tests showed that the new virus clearly differed from PAMV and PVX. Immuno-electron microscopy with antiserum to PepMV (1), the original PepMV isolate, and the virus from tomato showed decoration titers of 1:800 (homologous) and 1:400, respectively. Neither virus reacted with antiserum to PVX, nor did PVX react with antiserum to PepMV. Results of host plant analysis with 17 plant species mostly resembled those expected for PepMV. Nucleotide sequence alignment of DNA fragments obtained by reverse-transcriptase polymerase chain reaction with a specific primer set for potexviruses, directed against the RNA polymerase region, showed 93% identity between PepMV and the virus from tomato, while homologies with PVX, PAMV, and other potexviruses were <60%. Results indicate that the potexvirus in tomato is PepMV. PepMV was first found in pepino (Solanum muricatum) in Peru in 1974 and described by Jones et al. in 1980 (1). This is the first report of a natural infection of tomato by PepMV. Reference: (1) R. Jones et al. Ann. Appl. Biol. 94:61, 1980.

Further Evidence that Shallot Yellow Stripe Virus (SYSV) Is a Distinct Potyvirus and Reidentification of Welsh Onion Yellow Stripe Virus as a SYSV Strain.

ABSTRACT An antiserum to shallot yellow stripe virus (SYSV) was raised and used in combination with a range of other antisera to potyviruses of Allium spp. in electron microscopic decoration experiments. The serological results corroborated an earlier finding that the type isolates of SYSV and Welsh onion yellow stripe virus (WoYSV) are closely related to each other and only distantly related to onion yellow dwarf (OYDV) and leek yellow stripe (LYSV) viruses, the two other major potyviruses infecting Allium spp. Moreover, the decoration results indicated that Japanese potyviruses named OYDV and Wakegi yellow dwarf virus are isolates of SYSV. Sequence analysis of the 3'-terminal regions of the SYSV and WoYSV ge-nomes revealed coat protein (CP) amino acid and 3'-nontranslated region (3'-NTR) nucleotide sequence identities of 95 and 89%, respectively. The CP amino acid and 3'-NTR nucleotide sequences of these viruses differed from those of OYDV and LYSV by >25 and >67%, respectively. The serological and molecular studies showed that SYSV and WoYSV are different strains of a potyvirus distinct from OYDV and LYSV. For priority reasons, we propose that these strains together with the Wakegi-type isolates of OYDV described in Japan be referred to as SYSV and that SYSV isolates from Allium spp. other than shallot be designated as the Welsh onion strain of SYSV (SYSV-Wo).