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Multiple carlaviruses infect various ornamental plants, often having limited host ranges and causing minor symptoms, yet often reducing yield or quality. In this study we have identified a mixed infection of butterbur mosaic virus (ButMV) and helenium virus S (HelVS) from a plant of veronica (Veronica sp.) showing foliar mosaic and distortion. Carlavirus-like particles were observed by transmission electron microscopy (TEM), and RNA from partially purified virions was amplified by random RT-PCR, yielding clones of 439–1,385 bp. Two partially overlapping clones including coat protein (CP) sequence, and two of four partial replicase clones, were closely related to ButMV-J (AB517596), previously reported only from butterbur (Petasites japonicus) in Japan. Two other partial replicase clones showed lower identity to multiple carlaviruses. Generic primers which amplify the 3′-terminal region of multiple carlaviruses yielded clones of three distinct sequences: (1) with 98% nt identity to HelVS; (2) ButMV-A, showing 82% nt identity to ButMV-J; and (3) ButMV-B, with 78% nt identity to each of ButMV-J and ButMV-A. Further amplification of upstream fragments revealed that ButMV-B had an internal deletion in TGB1, confirmed using isolate-specific primers. Near-complete genomes of both ButMV-A and ButMV-B were obtained from next-generation sequencing (NGS), confirming the deletion within ButMV-B, which is presumably maintained through complementation by ButMV-A. HelVS was previously reported only from Helenium hybrids and Impatiens holstii. A near-complete HelVS genome was obtained for the first time by NGS from the same sample. Additional Veronica hybrids infected with HelVS were identified by TEM and RT-PCR, including cv. ‘Sunny Border Blue’ which was also subjected to NGS. This resulted in assembly of an 8,615 nt near-complete HelVS genome, with high identity to that from the mixed infection. The predicted CP sequence has 96% amino acid (aa) identity to HelVS from helenium (Q00556). Other ORFs show a maximum of 54% (TGB3) to 68% (NABP) aa identity to the equivalent ORFs of other carlaviruses. These results demonstrate for the first time maintenance by complementation of a carlavirus isolate with a major deletion in an essential gene, and confirm that HelVS is a distinct species in the genus Carlavirus.

Caulimoviridae is a family of non-enveloped reverse-transcribing plant viruses with non-covalently closed circular dsDNA genomes of 7.1–9.8 kbp in the order Ortervirales. They infect a wide range of monocots and dicots. Some viruses cause economically important diseases of tropical and subtropical crops. Transmission occurs through insect vectors (aphids, mealybugs, leafhoppers, lace bugs) and grafting. Activation of infectious endogenous viral elements occurs in Musa balbisiana, Petunia hybrida and Nicotiana edwardsonii. However, most endogenous caulimovirids are not infectious. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Caulimoviridae, which is available at ictv.global/report/caulimoviridae.

Bermuda grass samples were examined by transmission electron microscopy and 28-30 nm spherical virus particles were observed. Total RNA from these plants was subjected to high-throughput sequencing (HTS). The nearly full genome sequence of a panicovirus was identified from one HTS scaffold. Sanger sequencing was used to confirm the HTS results and complete the genome sequence of 4404 nt. This virus was provisionally named Bermuda grass latent virus (BGLV). Its predicted open reading frames follow the typical arrangement of the genus Panicovirus. Based on sequence comparisons and phylogenetic analyses BGLV differs from other viruses and therefore taxonomically it is a new member of the genus Panicovirus, family Tombusviridae.

A previous report (1) drew attention to the occurrence in the U.S. of tobacco rattle tobravirus (TRV) in several perennial ornamentals that move freely in international trade. Here we report the occurrence of TRV in an additional host plant of this type. The virus was identified in anemone (Anemone × hybrida cv. Honorine Jobert) with leaf symptoms consisting of chlorotic blotches, chlorotic line patterns, and distortion. Characteristic tobravirus-like particles with modal lengths of 50, 80, 130, and 180 nm were observed by electron microscopy in partially purified extracts of symptomatic but not of asymptomatic plants. These particles reacted specifically with antibodies to TRV and pea early-browning (PEBV) tobraviruses in immunoelectron microscopic (IEM) assays, produced typical TRV-induced symptoms in Nicotiana benthamiana and N. clevelandii, in which similar particles were detected by IEM, but, like other TRV isolates, did not infect pea (2). No other viruslike particles were observed in partially purified extracts of symptomatic anemone plants. This is the first report of TRV infection in anemone. While TRV occurs widely in Europe, it had been identified previously in the U.S. only in Oregon, Washington, and California (1,2,3). This virus is an important pathogen of several crops, including potato. Several areas of the Midwest, including Minnesota and Wisconsin, have significant seed-potato industries, and further introduction and possible dissemination of TRV pose potential regulatory and quarantine issues. This example of the movement of an exotic pathogen of potential economic importance into new areas underlines the need for closer monitoring of plant material entering international trade in an era of increasing globalization. References: (1) B. E. Lockhart et al. Plant Dis. 79:1249, 1995. (2) B. E. L. Lockhart and H. U. Fischer. Phytopathology 66:1391, 1976. (3) J. M. Crosslin and P. E. Thomas. Am. Potato J. 72:605, 1995.

Unusually severe leaf yellowing symptoms, similar to those described for yellow leaf syndrome (1), have been observed in several sugarcane clones in Guadeloupe since 1994, and since 1997 in Martinique. Leaf samples exhibiting various types of yellowing were taken from five different sugarcane clones, and analyzed by immunosorbent electron microscopy. Spherical particles, 24 to 28 nm in diameter and characteristic of luteoviruses, were found in two of five samples. The two infected samples showed yellowing on the underside of the midrib and one had a pinkish coloration on the upper side. The presence of sugarcane yellow leaf virus (ScYLV), the causal agent of sugarcane yellow leaf disease, was confirmed by reverse transcription-polymerase chain reaction (2) in these two samples and in 36 of 184 sugarcane clones bred in Guadeloupe and sent to Cirad's quarantine station in Montpellier, France. Following these observations, surveys were undertaken with a tissue blot enzyme immunoassay to analyze the distribution of ScYLV in sugarcane clones in the French West Indies. The midrib base of the first visible dewlap leaf was used to detect the presence of the virus in the phloem. In a first survey, clones of various origins worldwide were taken from germplasm collections. Two to three leaf samples per clone were analyzed from 78 clones in a collection in Guadeloupe and from 36 in a collection in Mar-tinique. Fifty of the 114 clones were infected by ScYLV, and ScYLV was detected in 21 of the 32 clones exhibiting severe leaf yellowing (score 3 or higher on a 1 to 5 scale). In a second survey, 19 leaf samples were taken from each of 53 clones from plants produced by Cirad's breeding program in Guadeloupe. The virus was detected in at least one sample for 25 of these 53 clones. ScYLV incidence in commercial fields was tested in Martinique in the variety B5992, which constitutes 57% of the cultivated area. Twenty leaves from different stools were sampled in six different fields, five of which had ScYLV-infected plants. The percentage of virus-infected stalks ranged from 0 to 90% whereas the percentage of stalks showing symptoms ranged from 50 to 100%. ScYLV appears widespread in the French West Indies, perhaps because a vector (Melanaphis sacchari) exists in Martinique and Guadeloupe. However, ScYLV was not found in all symptomatic plants, indicating that even if this luteovirus is a causal agent of leaf yellowing in the French West Indies, there may be other causal agents as well. References: (1) J. C. Comstock et al. Sugar J. 3:33, 1994. (2) J. C. Comstock et al. Sugar Cane 4:21, 1998.

Yellow ringspotting and concentric line patterns in plants of Dicentra (bleeding heart), Epimedium (barrenwort), and Heuchera (coral bells) from commercial nurseries and home gardens in Minnesota, Michigan, and Massachusetts were associated with infection by Tobacco rattle virus (TRV), which was identified by particle morphology, enzyme-linked immunosorbent assay and immunosorbent electron microscopy. No other viruslike particles were observed by electron microscopy in partially purified preparations of TRV-infected leaf tissue, and TRV was not detected in asymptomatic plants. This is the first report of TRV occurrence in Dicentra in the United States and the first report of TRV occurrence in Epimedium and Heuchera. In previous reports (1,2) we have called attention to the increasing incidence of TRV in vegetatively propagated perennial ornamental plant species in the United States and to the potential for virus spread to crops such as potato, in which TRV has not been reported in the midwestern United States. It is possible that increased international trade in vegetatively propagated ornamental plants may be resulting in the introduction of TRV and other exotic viruses into the United States and elsewhere. It is also possible that the natural occurrence of TRV in North America may be actually more widespread than has been reported. References: (1) B. E. Lockhart et al. Plant Dis. 79:1249, 1995. (2) B. E. Lockhart and J. A. Westendorp. Plant Dis. 82:712, 1998.

Banana streak badnavirus (BSV) is the most widely occurring virus in banana and plantain (1) but has not been reported to be a significant problem in commercial export bananas. In early 1999, the first severe outbreak of BSV infection in commercial export bananas (Musa AAA cv. Grand Nain) was recorded at Siquirres on the Atlantic coast of Costa Rica. Disease incidence in the plantation was 60% and symptoms included foliar chlorotic streaks, stunting of plants, splitting and internal necrosis of pseudostems and fruits, cigar leaf necrosis, and bunch emergence through the pseudostem. Diseased plants within a 0.8 ha area were eliminated to prevent possible further spread of the disease. The presence of BSV in diseased plants was confirmed by enzyme-linked immunosorbent assay and immunosorbent electron microscopy (1). Cucumber mosaic virus and Banana mild mosaic virus, which also occur in banana and plantain in Latin America (2), were not detected in the plants tested. Other recent accounts of BSV occurrence in commercial banana plantations in South America (our unpublished results) suggest that BSV occurrence in export bananas may be more significant than previously thought. References: (1) F. Gauhl et al. Int. J. Pest Management 45:167, 1991. (2) D. R. Jones, ed. 1999. Diseases of Banana, Abacá and Enset. CABI Publishing, Wallingford, U.K.

In Costa Rica, sugarcane plants with symptoms similar to those described for yellow leaf syndrome (YLS) (1,2) were first observed in 1994 in research plots of imported material in the midland areas of San Carlos and Turrialba. Recently, the same symptoms have been observed in commercial plantations in Turrialba. Symptomatic plants were characterized by yellowing of the leaves and central veins, the yellowing being more intense near the leaf tips. In severe cases, veins became reddish, and necrosis developed along the leaf edges, beginning at the leaf tip and extending to the base of the leaf. Growth of stems and roots was also reduced in infected plants. Minipurifications of six plants of four different varieties were examined by immunospecific electron microscopy (ISEM) using polyclonal antibodies (1). They were: one symptomatic plant each of the varieties H782313 and H608521; two symptomatic plants of H657052, and one asymptomatic plant each of H608521 and H827318. Isometric particles of approximately 28 nm were observed in the asymptomatic H827318 plant and in all symptomatic plants, with the exception of one plant of H657052. The size and morphology of the particles was similar to those reported for Sugarcane yellow leaf virus (ScYLV) (2). The presence of ScYLV was verified by indirect enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies (1). Twenty-two of 24 symptomatic plants and five of 13 asymptomatic plants were positive for ScYLV. These findings confirm the association of ScYLV with the yellows syndrome of sugarcane observed in Costa Rica. However, as was also reported by Scaglusi and Lockhart (1), ScYLV was not detected in several symptomatic plants, and research is continuing to determine whether other pathogens are associated with this syndrome in Costa Rica. References: (1) S. Scagliusi and B. E. L. Lockhart. Phytopathology 90:120, 2000; (2) J. Vega et al. Plant Dis. 81:21, 1997.

Sugarcane yellow leaf virus (SCYLV) was detected for the first time in 1996 in the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) sugarcane quarantine at Montpellier by reverse transcription-polymerase chain reaction (RT-PCR) in varieties from Brazil, Florida, Mauritius, and Réunion. Between 1997 and 2000, the virus was found by RT-PCR and/or tissue-blot immunoassay (TBIA) in additional varieties from Barbados, Cuba, Guadeloupe, Indonesia, Malaysia, Philippines, Puerto Rico, and Taiwan, suggesting a worldwide distribution of the pathogen. An excellent correlation was observed between results obtained for the two diagnostic techniques. However, even though only a few false negative results were obtained by either technique, both are now used to detect SCYLV in CIRAD's sugarcane quarantine in Montpellier. The pathogen was detected by TBIA or RT-PCR in all leaves of sugarcane foliage, but the highest percentage of infected vascular bundles was found in the top leaves. The long hot water treatment (soaking of cuttings in water at 25°C for 2 days and then at 50°C for 3 h) was ineffective in eliminating SCYLV from infected plants. Sugarcane varieties from various origins were grown in vitro by apical bud culture and apical meristem culture, and the latter proved to be the most effective method for producing SCYLV-free plants.

A filamentous virus identified in coleus (Coleus × hybrida) in Minnesota and New York was found to cause veinal necrosis in coleus, although this symptom was observed only under certain conditions. The virus was transmitted readily by mechanical inoculation to coleus and Nicotiana spp. and was not transmitted by Myzus persicae. The particles of the coleus virus had a modal length of 640 nm and a single capsid protein with an estimated molecular mass of 34 kDa. The amino acid sequence of the coat protein region of the coleus virus genome had significant similarities only to the corresponding domain of carlaviruses. Based on virion morphology, capsid protein size, genome size and organization, amino acid sequence, and phylogenetic analyses, the coleus virus, which was named provisionally Coleus vein necrosis virus (CVNV), was concluded to be a new definitive member of the genus Carlavirus. A 2-kb fragment of the 3′ terminus of the CVNV genome sequence is accessible under accession number DQ915963 in GenBank.

In October of 2005, a field survey was done in the province of Piura in northern Peru to determine the cause of a disease known locally as “mosaico” that was affecting organic Cavendish banana (Musa AAA) grown for the export market. Disease symptoms consisted of pronounced chlorotic and necrotic lesions on leaves of affected plants. Twenty-four farms were visited, and at each location, 10 randomly selected plants at flowering stage were evaluated for disease incidence and severity. Plants showing virus-like symptoms were observed in 18 of the 24 locations (75%). Fifty-two banana leaf samples, 27 from plants showing virus-like symptoms and 25 from asymptomatic plants, were tested for the presence of Banana streak virus (BSV), Cucumber mosaic virus (CMV), and Banana mild mosaic virus (BanMMV) by immunosorbent electron microscopy (ISEM) using partially purified leaf tissue extracts (2).The same extracts were also tested by immunocapture PCR (IC-PCR) for presence of BSV and specific BSV isolates (BSV-OL, BSV-GF, BSV-IM, and BSV-CAV) using badnavirus-specific degenerate primers and BSV isolate-specific primers, respectively (1). Seventeen of 27 leaf samples showing virus-like symptoms (63%) tested positive for BSV by ISEM and IC-PCR using badnavirus, but not isolate-specific, primers. The symptoms on the 10 samples that tested negative were not typical of BSV infection. One asymptomatic leaf sample (4%) also tested positive for BSV. To validate the PCR results, the nucleotide sequence of the amplicon from a plant showing the most prevalent foliar symptom type was determined. This sequence (GenBank Accession No. DQ674317) had ≤86% homology to the corresponding ORF III polyprotein region of BSV and other badnaviruses. Neither CMV nor BanMMV was detected in any of the 52 samples tested. From these results, it was concluded that “mosaico” disease of organic Cavendish bananas in northern Peru is associated frequently with BSV infection and that there is a high incidence of BSV infection in this area. To our knowledge, this is the first report of BSV occurrence in Peru. It was both surprising and interesting that neither BSV-OL nor BSV-GF, the two BSV isolates found most commonly in banana (Musa AAA) and plantain (Musa AAB) in South and Central America (B. E. L. Lockhart, unpublished), was detected in Cavendish banana in northern Peru. Failure to detect BSV-OL and BSV-GF suggests that field infection may be due to vertical transmission by clonal propagation rather than to horizontal transmission from local plantain and that control of “mosaico” disease could therefore be achieved by use of virus-free planting material. References: (1) A. D. W. Geering et al. Phytopathology 90:921, 2000. (2) B. E. L. Lockhart et al. Phytopathology 82:921, 1992.

This report describes the complete nucleotide sequence and genome organization of Rosa rugosa leaf distortion virus (RrLDV), the causal agent of a previously undescribed virus disease of Rosa rugosa. The RrLDV genome is a positive-sense ssRNA, 3971 nucleotides in length, containing five open reading frames (ORFs). ORF1 encodes a 27-kDa peptide (p27). ORF2 shares a common start codon with ORF1 and continues through the amber stop codon of p27 to produce an 87-kDa protein (p87) with amino acid sequence similarity to the RNA-dependent RNA polymerases (RdRp) of members of the family Tombusviridae. ORF3 encodes a protein of 8 kDa with no significant similarity to known viral sequences. ORF4 encodes a 6-kDa protein (p6) with similarity to the p13 movement proteins of members of the family Tombusviridae. ORF5 has no conventional start codon and overlaps with p6. A putative +1 frame shift mechanism allows p6 translation to continue through the stop codon and results in a 12-kDa protein with high homology to the carmovirus p13 movement protein. The 37-kDa protein encoded by ORF6 has amino acid sequence similarity to coat proteins (CPs) of members of the family Tombusviridae. Phylogenetic analyses of the RdRp and CP amino acid sequences placed RrLDV in a subgroup close to members of the genus Carmovirus of the family Tombusviridae.

Clematis chlorotic mottle virus (ClCMV) is a previously undescribed virus associated with symptoms of yellow mottling and veining, chlorotic ring spots, line pattern mosaics, and flower distortion and discoloration on ornamental Clematis. The ClCMV genome is 3,880 nt in length with five open reading frames (ORFs) encoding a 27-kDa protein (ORF 1), an 87-kDa replicase protein (ORF 2), two centrally located movement proteins (ORF 3 and 4), and a 37-kDa capsid protein (ORF 5). Based on morphological, genomic, and phylogenetic analysis, ClCMV is predicted to be a member of the genus Pelarspovirus in the family Tombusviridae.

This report describes the complete nucleotide sequence and genome organization of rose yellow vein virus (RYVV), a proposed new member of the family Caulimoviridae. The RYVV genome is 9314 bp in size and contains eight open reading frames (ORFs). ORFs 1, 2, and 3 have 22-38 % amino acid sequence similarity to known members of the family Caulimoviridae. The remaining ORFs have no significant amino acid sequence similarity to known viruses. Based on differences in its genome organization, its low sequence similarity to known members of the family Caulimoviridae, and the results of phylogenetic analysis, RYVV appears to be a distinct new member of this family.

Rubus yellow net virus (RYNV) infects Rubus species and cultivars worldwide and is an essential component of raspberry veinbanding mosaic (RVBMD), a virus disease complex that causes serious decline in plant vigour and productivity. The virus is transmitted, probably in a semi-persistent manner, by the large raspberry aphid, Amphorophora idaei in Europe, and A. agathonica in North America. The particles of RYNV are bacilliform in shape and measure 80-150 × 25-30 nm, similar to those of badnaviruses. A 1.7 kb fragment of the viral DNA was amplified by PCR and then directly sequenced. Analysis of this sequence suggests that RYNV is possibly a distinct species in the genus Badnavirus and is most closely related to Gooseberry vein banding associated virus (GVBAV) and Spiraea yellow leaf spot virus, two other badnaviruses described recently. Using the sequence derived from the PCR-amplified viral DNA fragment, RYNV-specific primers were designed and used in PCR to assay for RYNV in a range of Rubus germplasm infected with RYNV, with other unrelated viruses and virus-like diseases found in Rubus, and in healthy plants. RYNV was detected in all glasshouse cultures of RYNV-infected plants, whether alone or in complex infections with other viruses, but not from healthy Rubus plants, nor from plants infected with other viruses. It was also detected in field-grown raspberry plants with and without symptoms of RVBMD and in raspberry plants infected with RYNV by viruliferous A. idaei. RYNV was also detected by PCR in A. idaei following access feeds on RYNV-infected plants of 1 h or more. PCR failed to amplify DNA from gooseberry infected with GVBAV confirming the specificity of the RYNV analysis. PCR detection of RYNV in dormant raspberry buds allows assays to be made outside the natural growing season, providing a useful application for plant introduction and quarantine programmes.

Two previously undescribed viruses were associated with a yellow leafspot disease of spiraea (Spiraea spp.) in the midwestern USA. The first virus, named spiraea leafspot virus (SLSV) is a badnavirus which has a 7.4 kb dsDNA genome and resembles other badnaviruses in particle and genome properties, but is unusual in being transmitted by an aphid (Aphis spiraecola) rather than by mealybugs. The second virus, which is also transmitted by A. spiraecola, has spherical 30-35 nm particles containing a 7.2 kb ds RNA genome. This virus was named spiraea leafspot spherical virus (SLSSV). In particle morphology and genome type SLSSV resembles some members of the family Totiviridae, none of which have been reported to infect plants or higher organisms. In the majority of cases SLSV and SLSSV occurred in mixed infections. Early-season symptoms were associated with the presence of SLSSV and absence of SLSV, whereas late-season symptoms were associated with the presence of SLSV and absence or greatly reduced levels of SLSSV.

Gooseberry vein banding disease (GVBD) affects Ribes species and cultivars worldwide. It is the second most important virus-like disease in these crops after black currant reversion disease. In this paper, we describe a bacilliform virus, Gooseberry vein banding associated virus (GVBAV), which is associated closely with GVBD, and provide evidence that GVBAV is a distinct species within the genus Badnavirus. Purified GVBAV particles were ca. 120 × 30 nm in size and contained dsDNA. The sequence of a 1.5-kb DNA fragment amplified from viral genomic DNA was similar to those of a wide range of badnaviruses and contained motifs characteristic of the RNase H domain of the badnavirus open reading frame (ORF) III polyprotein. Phylogenetic analyses suggest that GVBAV is most closely related to Spiraea yellow leaf spot virus. Using sequence derived from the polymerase chain reaction (PCR)-amplified DNA fragment, virus-specific primers were designed. These primers were used in PCR to assay for GVBAV in a range of Ribes germplasm affected with GVBD, with other unrelated virus-like diseases and viruses found in Ribes, and in healthy plants. GVBAV was detected in all of 58 GVBD-affected plants from diverse sources, but not from healthy Ribes plants nor from plants infected with other viruses.

The genome of the rose yellow leaf virus (RYLV) has been determined to be 3918 nucleotides long and to contain seven open reading frames (ORFs). ORF1 encodes a 27-kDa peptide (p27). ORF2 shares a common start codon with ORF1 and continues through the amber stop codon of p27 to encode an 87-kDa (p87) protein that has amino acid similarity to the RNA-dependent RNA polymerase (RdRp) of members of the family Tombusviridae. ORFs 3 and 4 have no significant amino acid similarity to known functional viral ORFs. ORF5 encodes a 6-kDa (p6) protein that has similarity to movement proteins of members of the Tombusviridae. ORF5A has no conventional start codon and overlaps with p6. A putative +1 frameshift mechanism allows p6 translation to continue through the stop codon and results in a 12-kDa protein that has high homology to the carmovirus p13 movement protein. The 37-kDa protein encoded by ORF6 has amino acid sequence similarity to coat proteins (CP) of members of the Tombusviridae. ORF7 has no significant amino acid similarity to known viral ORFs. Phylogenetic analysis of the RdRp amino acid sequences grouped RYLV together with the unclassified Rosa rugosa leaf distortion virus (RrLDV), pelargonium line pattern virus (PLPV), and pelargonium chlorotic ring pattern virus (PCRPV) in a distinct subgroup of the family Tombusviridae.

A previously uncharacterized luteovirus was associated with one form of yellow leaf syndrome (YLS), a widespread disease of sugarcane (Saccharum sp.). The virus was named Sugarcane yellow leaf luteovirus (ScYLV), and was identified in major sugarcane-producing areas of the world. Typical disease symptoms were reproduced when ScYLV was transmitted by Melanaphis sacchari or Rhopalosiphum maidis from infected to healthy sugarcane, suggesting that this virus may be the causal agent of one form of YLS. The only known hosts of ScYLV are Saccharum and Erianthus spp. Virions of ScYLV were 24 to 29 nm in diameter in sodium phosphotungstate at pH 5.0, had a buoyant density of 1.30 g/cm3 in Cs2SO4, and contained a 5.8-kb genomic ssRNA. The capsid protein had an estimated relative molecular mass of 27 kDa and was not glycosylated. A polyclonal rabbit antiserum raised against ScYLV did not detect any of eight other luteoviruses by enzyme-linked immunosorbent assay or immunosorbent electron microscopy, but in immunoblot assays, antibodies to ScYLV detected the RPV serotype of Barley yellow dwarf luteovirus. It is concluded that ScYLV is a previously undescribed luteovirus that is biologically and serologically distinct from other members of the group and may be the causal agent of one form of YLS of sugarcane.

Micropropagated plants of 36 Musa genotypes with diverse genetic backgrounds, including 14 tetraploid plantain (TMPx) and banana (TMBx) hybrids, were evaluated for their response to banana streak badnavirus (BSV) infection under three environments from 1995 to 1997 in Nigeria. The characteristics evaluated were the natural incidence of BSV based on symptoms and virus indexing, relative concentration of BSV antigens in leaf tissues determined by ELISA, and some growth and yield descriptors. Virus occurrence and symptom expression, as well as the relative concentration of BSV antigens, fluctuated greatly between seasons during the cropping cycle, being high during the rainy season and low or negligible during the hot dry season. The natural incidence of plants with symptoms and BSV-infected plants varied between genotypes. Incidence of BSV on most International Institute of Tropical Agriculture (IITA) TMPx hybrids and three Fundacion Hondureoa de Investigacion Agricola (FHIA) hybrids was high in the three environments, with some variation. Most landraces and some FHIA or Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA) hybrids were not BSV-infected under either environment at Onne. However, a few expressed some foliar symptoms at Ibadan and indexed BSV positive. The relative concentration of BSV antigens in leaf samples was also high in most TMPx and some FHIA hybrids, but low in most landraces. While BSV infection had no significant effect on most growth characteristics, it had a highly variable effect on bunch weight loss among the genotypes. There was no relationship between the natural incidence of BSV, concentration of viral antigen and bunch weight loss among the 11 TMPx hybrids, three FHIA hybrids and three plantain landraces. Despite the high natural BSV incidence and the high relative antigen concentration in their leaf tissue, TMPx 548-9, TMPx 2637-49, TMPx 7002-1 and FHIA 21 suffered less than 15% bunch weight loss, and TMPx 548-4 and FHIA 22 suffered no loss. These results suggest that under the conditions specified in this study, these hybrids could be tentatively classified as ‘field tolerant’ to BSV.

Summary Between 1991 to 1996, more than 50 Musa hybrids and 10 landraces were evaluated under field and screenhouse conditions for virus symptoms resembling those caused by banana streak badnavirus (BSV). The symptoms included chlorotic streaks, leaf deformation, stunting, cigar leaf death, distortion of the peduncle, bunch or fruits, and internal pseudostem necrosis. Immunosorbent electron microscopy (ISEM) of randomly selected plants with one or more of these symptoms confirmed the presence of BSV particles in 15 tropical Musa plantain hybrids (TMPx) and five Musa landraces. Under both field and screenhouse conditions, the incidence of symptomatic plants in the hybrids was significantly higher than in the landraces. The hybrids also generally had a higher concentration of BSV antigens, as determined by enzyme-linked immunosorbent assay (ELISA). By contrast, most BSV-infected landraces were symptomless and had very low or undetectable amounts of BSV antigens. There was a significant variation in incidence of symptomatic plants between genotypes, experiments and year of observation. These results are discussed in relation to the higher natural BSV incidence observed on some Musa hybrids as compared with their parental genotypes.

Plantain orchards in the major plantain production area in southern Nigeria were surveyed in 1995 for the occurrence of banana streak virus (BSV) disease. Plantain plants showing BSV-like symptoms were found in 37 of 71 villages visited and in 49 of 147 orchards. BSV was positively identified by ISEM and/or ELISA in 30 orchards in 27 villages. The incidence of symptomatic plants in an orchard ranged from 1 to 17% (mean 4.2%). Of 58 leaf samples taken from plants with symptoms and indexed for both BSV and cucumber mosaic virus (CMV), 36 (62%) tested positive for BSV and none tested positive for CMV. The survey results show that BSV is common and widespread in the plantain-growing area of southern Nigeria.

Summary A Nigerian isolate of banana streak badnavirus (BSV) was purified and a polyclonal antiserum was produced in mice. The antiserum titre was between 1:10 000 and 1:40 000 in enzyme linked immunosorbent assay (ELISA), and showed a good specificity to BSV antigens. Comparative tests were carried out to determine the sensitivity and reliability of BSV antigen detection by double antibody sandwich (DAS)-ELISA, triple antibody sandwich (TAS)-ELISA, antigen coated plate (ACP)-ELISA, and protein-A coated antibody sandwich (PAS)-ELISA. TAS-ELISA using rabbit polyclonal antiserum to trap BSV and mouse polyclonal antiserum to detect the virus particles, was more sensitive than ACP-ELISA and PAS-ELISA and detected BSV in plant extracts from both symptomatic and some asymptomatic plants. However, immunosorbent electron microscopy detected more BSV-infected plants from asymptomatic plant samples than did TAS-ELISA. Results of this study showed that detection of BSV antigens in sap extracts by TAS-ELISA was most efficient with symptomatic tissues which occurred most frequently in the ‘cool rainy’ season. This suggests that for more reliable BSV-indexing of field samples, tissue sampling should be done during the rainy season when most BSV-infected plants express severe symptoms.

The effect of temperature on symptom expression and detection of banana streak badnavirus (BSV) by immunosorbent electronmicroscopy (ISEM) and enzyme-linked immunosorbent assay of 12 in vitro-propagated plantain hybrids (genome AAB × AA), 3 ABB cooking banana, and 3 AAB plantain landraces was studied. Experiments were done for 2 years under two temperature regimes, 28 to 35°C in a screenhouse and 22°C in a temperature-controlled room. Most BSV-infected plants of plantain hybrids expressed symptoms under both conditions. Symptom expression was enhanced when plants were continuously grown at 22°C, but later became indiscernible when plants were continuously grown at 28 to 35°C. Plants grown at 22°C and showing severe symptoms contained significantly higher virus titer than plants grown at 28 to 35°C. When asymptomatic plants with very low virus titer at 28 to 35°C were transferred back to 22°C, there was a significant increase in both symptom severity and concentration of virus (greater than 3 to 5 times) in leaf tissues after 9 months. In contrast, the concentration of virus and symptom severity decreased in plants after transfer from 22°C to 28 to 35°C. Micropropagated plants of AAB plantain landrace cv. Mimi Abue and ABB cooking bananas (cvs. Bluggoe, Cardaba, and Pelipita) did not express visible symptoms under either temperature regime, but BSV was detected by ISEM in 23% of the plants. After 2 years at 22°C, virus was detected in 64% of the plants, but the concentration of virus remained low. Implications of these results on quarantine screening of in vitro plants and virus diagnosis are discussed.

Streak disease of banana and plantain caused by banana streak virus (BSV) was first reported in the Ivory Coast in 1974 and occurs in at least 16 countries in Africa. Based on genomic characteristics, BSV has been shown to be a member of genus Badnavirus. Efficient and reliable diagnostic methods for BSV have recently become widely available. This paper summarizes the current knowledge on its causal agent, geographical distribution, symptomatology, transmission, host range, available diagnostic techniques and management options for the disease in Africa. Further research needs are identified in light of the widespread occurrence of BSV in most plantain/banana germplasms and the difficulties in obtaining BSV-free plantlets through tissue culture.

A previously undescribed virus with flexuous filamentous particles 720 nm in length was associated with a mosaic disease of ash (Fraxinus spp.) occurring in Minnesota, Ohio, New York, and Illinois. The virus was initially identified in white ash in Minnesota and named white ash mosaic virus (WAMV), but also occurred naturally in green, black, and blue ash. The virus was transmitted readily by mechanical inoculation and was determined to be the causal agent of the disease. It infected only ash, and was not transmitted through seed or by Myzus persicae. The virus has a ssRNA genome of approximately 9.0 kb and a capsid protein of ∼34 kDa based on electrophoretic analysis. One partial and five complete putative ORFs most similar in size, arrangement, and amino acid sequence to the corresponding genomic regions of flexiviruses were identified in a 5227 nt 3′ terminal fragment of the WAMV genome (GenBank accession no. GU906791.1). However, the relatively low levels (27-59%) of amino acid sequence identity suggests that WAMV is not related closely to any known member of the family Flexiviridae. White ash mosaic virus was identified in Minnesota in black ash trees showing symptoms of ash decline, a syndrome of wide occurrence and possible multiple etiology. Antibody and PCR-based protocols were developed for reliable detection of WAMV in ash and will be made available upon request. Accepted for publication 3 January 2012. Published 9 May 2013.

The complete genomic sequence of rose yellow mosaic virus (RoYMV) was determined and found to have all the features that are characteristic of members of the family Potyviridae. The RoYMV genome is 9508 nucleotides long excluding the 3′-poly-(A) tail and contains a single open reading frame encoding a polyprotein of 3067 amino acids. The RoYMV P3 and CI cistrons are shorter than those of other members of the family Potyviridae, and the 6K1 cistron is completely absent. Comparative sequence analysis revealed that RoYMV had highest amino acid sequence identity across the entire genome sequence to brome streak mosaic virus (33 %) and to turnip mosaic virus (30 %) at the coat protein level. Based on its low sequence similarity to known members of the family Potyviridae and phylogenetic analysis, RoYMV appears to be a distinct, previously undescribed, member of this family.

The genome of sugarcane bacilliform virus (ScBV), a badnavirus, consists of a circular dsDNA. The complete sequence of a cloned infective ScBV genome is reported here. The genome is 7568 bp in size and possesses a number of features suggesting that ScBV is a pararetrovirus. A tRNA(Met)-binding site that may serve as a primer for minus-strand synthesis is present. The plus-strand of the ScBV genome contains three open reading frames (ORFs) which are capable of encoding proteins with calculated M(r) values of 22K, 13K and 215K. The 215K protein has regions with similarity to the RNA-binding domains, aspartic proteases and replicases of retro-elements. In addition, the 215K protein also has a region with restricted similarity to the intercellular transport proteins of plant viruses. Comparisons with the other sequenced badnaviruses, Commelina yellow mottle (CoYMV) and rice tungro bacilliform (RTBV) viruses, indicate that the arrangement of the ORFs in these viruses is conserved. Located next to the putative RNA-binding domain is a cysteine-rich region that is unique to the badnaviruses. When the molecular relationships of a portion of the reverse transcriptases of plant pararetroviruses were determined, two badnaviruses, CoYMV and ScBV, form one distinct cluster, whereas three caulimoviruses, cauliflower mosaic virus, carnation etched ring virus and figwort mosaic virus, form a second cluster. The badnavirus RTBV and the caulimovirus soybean chlorotic mottle virus occupy intermediate positions between the clusters. When introduced by Agrobacterium-mediated inoculation, a construct containing 1.1 copies of the cloned ScBV genome is infectious to both rice and banana.

Commelina yellow mottle virus (CoYMV) is a double-stranded DNA virus that infects the monocot Commelina diffusa. Although CoYMV and cauliflower mosaic virus (CaMV; another double-stranded DNA virus) probably replicate by a similar mechanism, the particle morphology and host range of CoYMV place it in a distinct group. We present evidence that a prompter fragment isolated from CoYMV confers a tissue-specific pattern of expression that is different from that conferred by the CaMV 35S promoter. When the CoYMV promoter is used to drive expression of the beta-glucuronidase reporter gene in stably transformed tobacco plants, beta-glucuronidase activity occurs primarily in the phloem, the phloem-associated cells, and the axial parenchyma of roots, stems, leaves, and flowers. Activity is also detected throughout the anther, with highest activity in the tapetum. In contrast, the CaMV 35S promoter is active in most cell types. The CoYMV promoter is a strong promoter, and when the activity of the CoYMV promoter is compared with that of a duplicated CaMV 35S promoter, it is 30% as active in tobacco suspension cells and up to 25% as active in maize suspension cells. These properties of the CoYMV promoter make it potentially useful for high-level expression of engineered genes in vascular cells.

Banana and plantain (Musa spp.) are grown in more than 125 countries (Anon., 2001) and are a major source of carbohydrate for more than 400 million people (Swennen et al, 1995). The progenitors of almost all domesticated Musa are two wild species, Musa acuminata and M. balbisiana, whose genomes are represented using the letter codes A and B, respectively. The most commonly cultivated cultivars have the triploid genotypes AAA, AAB or ABB.

The 5895 nucleotide long single-stranded RNA genome of Sugarcane yellow leaf virus Florida isolate (SCYLV-F) includes six major ORFs. All but the first of these are homologous to genes of known function encoded by viruses of the three newly defined genera in the Luteoviridae (‘luteovirids’), i.e. poleroviruses, luccccteoviruses and the enamoviruses. SCYLV-F ORFs 1 and 2 are most closely related to their polerovirus counterparts, whereas SCYLV-F ORFs 3 and 4 are most closely related to counterparts in luteovirus genomes, and SCYLV-F ORF5 is most closely related to the read-through protein gene of the only known enamovirus. These differences in affinity result from inter-species recombination. Two recombination sites in the genome of SCYLV-F map to the same genomic locations as previously described recombinations involving other luteovirids. A fourth type of luteovirid, Soybean dwarf virus, has already been described. Our analyses indicate that SCYLV-F represents a distinct fifth type.

Hostas (Hosta spp.) are one of the most widely grown and economically important landscape perennials in the nursery industry in North America. Several viruses including Hosta virus X (HVX), Tobacco rattle virus (TRV), Tobacco ringspot virus (ToRSV), Tomato ringspot virus (TomRSV), Impatiens necrotic spot virus (INSV), and Tomato spotted wilt virus (TSWV) are known to occur in hostas (4). This report confirms the occurrence of an additional virus, Arabis mosaic virus (ArMV), in hostas in North America. This virus was first identified during the summer of 2004 in Hosta fortunei ‘Sharmon’ in several garden centers in Minneapolis and St. Paul, MN. Entire lots of this variety, numbering several dozen plants, showed symptoms consisting of blanching of the foliage similar to those caused by ToRSV and TomRSV infection (4). Symptoms persisted throughout the growing season. Virus-like particles, 28 to 30 nm in diameter, were observed by electron microscopy in partially purified extracts of symptomatic leaf tissue following fixation with 5% glutaraldehyde and negative staining with 2% sodium phosphotungstate, pH 7.0. Particles had an angular outline and some were penetrated by stain. No other virus-like particles were observed in these extracts. The particles were identified as those of ArMV. Identification was made using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and immunosorbent electron microscopy (ISEM) with antiserum to ArMV (PVAS-587) obtained from the American Type Culture Collection, Manassas, VA. In the spring and summer of 2005, ArMV was again identified as described above in ‘Sharmon’, H. undulata ‘Albomarginata’ samples from Minnesota, Michigan, and Nebraska, and H. ‘Marion Bachman’ and H. ‘Touch of Class’ from two wholesale nurseries in Minnesota. Symptoms in these hosta cultivars were similar to those observed in ‘Sharmon’ and were accompanied by stunting and leaf deformation. A portion of the coat protein (CP) gene of the ArMV isolate from ‘Sharmon’, designated ArMV-H, was amplified using reverse transcription-polymerase chain reaction (RT-PCR) with ArMV-specific CP primers (3) and total RNA extracted with a RNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). Amplicons of the expected size (220 bp) were cloned and five clones were sequenced. Nucleotide sequence identities of the ArMV-H CP sequence to corresponding ArMV databank entries varied from 94 to 88% (Genbank Accession Nos. AY017339 and D10086 and X55460 and X81815, respectively). Interestingly, the hosta ArMV isolate was not transmitted by mechanical inoculation to diagnostically susceptible indicator plants (cucumber, tobacco, and petunia) (2) or to hosta (H. undulata ‘Albormarginata’, H. ‘Honeybells’, and H. ‘Royal Standard’). Testing by using ELISA and ISEM showed that ‘Sharmon’ source plants contained high levels of ArMV antigen and virions, and a high percentage of virions were not penetrated by negative stain, indicating that they were not empty (i.e., devoid of RNA). It appears that ArMV-H may be transmitted only vertically, (i.e., clonal propagation) and this raises some interesting questions about the molecular basis of this anomaly. An isolate of ArMV from hops was similarly reported to have a very restricted host range (1) suggesting a possibility of a common mechanism of host range restriction. References: (1) K. R. Bock. Ann. Appl. Biol. 57:431, 1966. (2) A. A. Brunt et al. Viruses of Plants. CAB Internacional Mycological Institute, Wallingford, UK, 1995. (3) P. Kominek et al. Acta Virol. 47:199, 2003. (4) B. E. L. Lockhart and S. Currier. Acta Hortic. 432:62, 1996.

Interest in virus diseases of perennial ornamentals has been increasing because of their increasing monetary value, because wholesale producers perceive an advantage in marketing disease-free stock, and because widespread international movement of these plants carries the risk of introduction of exotic viruses. In an ongoing study to identify and document viral diseases of perennial ornamentals used in the United States commercial horticultural industry, three virus-like diseases of astilbe (Astilbe chinensis), fuschia (Fuschia cv. Gartenmeister) and false lupine (Thermopsis caroliniana) occurring in Minnesota were investigated. Symptomatic plants were selected from lots in commercial greenhouses and garden centers in several locations in Minnesota. Astilbe with systemic chlorosis was found to be infected with Tobacco ringspot virus (TRSV). Fuschia with leaf mottling and leaf deformation was found to be infected with Cucumber mosaic virus (CMV), and false lupine with mosaic and leaf deformation symptoms was found to be infected with Bean yellow mosaic virus (BYMV). Identification of the three viruses was based on: 1) virion presence and morphology in partially purified leaf extracts using electron microscopy (EM) and immunosorbent electron microscopy (1); 2) enzyme-linked immunosorbent assay using crude leaf extracts; and 3) biological properties, including symptoms produced in indicator plants. Antisera to BYMV (ATCC PVAS-368), CMV (ATCC PVAS-30), and TRSV (ATCC PVAS-157) were obtained from the American Type Culture Collection, Manassas, VA. No other virus-like particles were observed with EM in partially purified leaf extracts of the three plants, no virus-like particles were observed in similar preparations from asymptomatic plants, and indicator plant tests did not indicate the presence of any other mechanically transmissible viruses. The TRSV isolate from astilbe and the BYMV isolate from false lupine produced typical symptoms on indicator plants susceptible to known isolates of these two viruses. The CMV isolate from fuschia was similar to previously described isolates of CMV (2) in most respects and was readily transmitted in a nonpersistent manner by Myzus persicae, but was unusual in that it did not infect Nicotiania benthamiana, N. glutinosa, and tomato, which are normally highly susceptible to infection by CMV. The identity of the fuschia CMV isolate was further confirmed by reverse transcription-polymerase chain reaction (RT-PCR) amplification with CMV-specific oligonucleotide primers (3). The PCR product was of the predicted size (500 bp) and was cleaved by restriction digestion with EcoRI, suggesting that the fuschia virus is a Type II CMV isolate (3). To my knowledge, this is the first report of TRSV infection in astilbe, CMV infection in fuschia, and of a viral disease of false lupine. References: (1) Y. C. Ahlawat et al. Plant Dis. 80:590, 1996. (2) A. A. Brunt et al. Viruses of Plants. CAB International, Wallingford, UK, 1995. (3) S. Wylie et al. Aust. J. Agric. Res. 44:41, 1993.

Petunia vein-clearing virus (PVCV), a tentative member of the caulimovirus group of plant pararetroviruses, was first identified in petunia (Petunia hybrida Vilm.) in Germany in the hybrid cv. Himmelröschen (1). A similar virus was recently identified in Minnesota in the petunia cv. Fantasy Pink grown from seed in commercial greenhouses. This virus has spherical particles 46 to 47 nm in diameter in preparations negatively stained with 1% uranyl acetate or sodium phosphotungstate, pH 7.0, and which contain a double-stranded DNA genome approximately 7.3 kb in size. The virus was shown by immunoelectron microscopy (IEM) to be closely related serologically to PVCV. No serological relationship to any other caulimoviruses was detected. Like PVCV, which is transmitted only by seed and grafting, the Minnesota virus isolate was not transmitted by mechanical inoculation to petunia or any other indicator plant. Symptoms associated with infection by PVCV in cv. Fantasy Pink consisted of mild vein clearing to severe vein yellowing, and reduction in leaf size and internode length. Symptoms were most frequently expressed when plants were under water and nutrient stress. Vigorously growing plants usually showed no symptoms, and no virions were detected by IEM in partially purified extracts from such plants. This suggests that infection of petunia hybrids by seed-borne PVCV may possibly be more widespread, but may go unnoticed because virus-induced symptoms may not be elicited in plants growing under favorable conditions. References: (1) D. Lesemann and R. Casper. Phytopathology 63:1118, 1973.

A previously undescribed closterolike virus with particles measuring 1,500-1,600 nm×12 nm was found in 11 cultivars of sugarcane (Sacchrum sp.) from Florida, Mauritius, and Malawi. The virus, which was named sugarcane mild mosaic virus (SCMMV), occurred in all cases in mixed infections with sugarcane bacilliform virus (SCBV). SCMMV was transmitted by mechanical inoculation to sugarcane, rice, Sorghum halepense, and S. bicolor with partially purified, concentrated extracts but not with crude sap (...)

(...) DNA extracted from CoYMV virions consists of linear and circular forms, which migrate separately in agarose gels. CoYMV genomic DNA appears to have two single-stranded discontinuities and was not shown to be infectious. Preliminary data on three other viruses similar to CoYMV in size and morphology-banana streak virus (BSV), canna yellow mottle virus (CaYMV), and Kalanchoe top-spotting virus (KaTSV)-indicate that they also contain double-stranded DNA of similar size. These plant viruses are of potential interest for use as vectors for gene transfer in higher plants

Guar is reported for the first time as a host of potato virus Y. The virus produced no symptoms, or occasional faint chlorotic spots on inoculated cotyledons and unifoliate leaves. No symptoms were observed on new growth, but the virus was consistently recovered from these leaves by back-inoculation to tobacco. Neither potato virus X nor cucumber mosaic virus infected guar.