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Characterization of a Potexvirus Infecting Hosta spp.
Abstract
A previously undescribed potexvirus, named Hosta virus X (HVX), was found in 17 naturally infected hosta (Hosta spp.) cultivars from Minnesota, Indiana, Illinois, Iowa, and Michigan. HVX was readily transmitted mechanically but infected only Nicotiana benthamiana and Hosta spp., in which symptoms ranged from severe mosaic and leaf necrosis to latency. Particles of HVX averaged 530 nm in length, had a buoyant density in cesium chloride of 1.28 gm/cm3, and contained a single genomic species of ssRNA approximately 3 kb in size. The capsid protein of HVX had a molecular mass of approximately 27 kDa. In indirect enzyme immunoassays, HVX reacted with an antiserum to clover yellow mosaic virus (ClYMV), and less strongly with antiserum to hydrangea ringspot virus (HRSV), but not with antisera to any of 14 other potexviruses tested. However, in reciprocal tests, ClYMV reacted only very weakly with HVX antiserum. HVX did not infect any of three cultivars of pea that were susceptible to infection by ClYMV, and ClYMV did not infect any of three hosta cultivars susceptible to infection by HVX. Spread of HVX infection in hosta appears to occur by vegetative propagation and accidental mechanical transmission, and management of the disease can be achieved by virus indexing and cultural practices that minimize the risk of virus spread to susceptible cultivars.
... Hosta virus X (HVX), the most common virus of hosta (Hosta spp.), was first identified and characterized in the USA in 1996 [6,15]. In nature, the virus has been isolated only from hostas, where the transmission occurs through seed, mechanical contact or vegetative propagation [6]. ...
... Hosta virus X (HVX), the most common virus of hosta (Hosta spp.), was first identified and characterized in the USA in 1996 [6,15]. In nature, the virus has been isolated only from hostas, where the transmission occurs through seed, mechanical contact or vegetative propagation [6]. Symptoms of HVX infection in hostas varies and includes mosaic, necrosis and leaf deformation as well as reduction in plant growth [16,21]. ...
... A total of 82 hosta plants constituting 31 different cultivars exhibiting various virus-like foliar symptoms including mosaic, mottling, leaf necrosis and leaf distortion were collected throughout Tennessee, USA [1], and indexed for the presence of HVX by squash immunoblotting assay using an antiserum against HVX CP [6,8]. Of 62 serologically positive plants [1], 30 isolates derived from 20 different hosta cultivars were selected and used in this study (Table 1). ...
Triple gene block 1 (TGB1) and coat protein (CP) sequences of 30 hosta virus X (HVX) isolates from Tennessee (TN), USA, were determined and compared with available sequences in GenBank. The CPs of all known HVX isolates, including those from TN, shared 98.3-100% and 98.2-100% nucleotide and amino acid sequence identity, respectively, whereas TGB1 shared 97.4-100% nucleotide and 97-100% amino acid sequence identity. TGB1 of TN isolates were all longer by one codon from that of a Korean isolate, which is the only sequence publicly available. Phylogenetic analysis of nucleotide and amino acid sequences of TGB1 and CP of all known HVX isolates, separately or combined, revealed a close relationship, suggesting that all of them are derived from a common ancestor. Phylogenetic analysis with the type member of each genus of the family Flexiviridae confirmed that HVX is a member of a distinct species of the genus Potexvirus.
... Hostas are popular perennial garden plants and new varieties are in high demand. Hosta X virus (Table 1), an easily transmitted potexvirus, was spread globally with a new variety before the causal agent for the leaf coloration was established (Currier and Lockhart 1996). Virus symptoms can also resemble phytotoxic responses to pesticide sprays or other chemicals, as in Euphorbia spp. ...
... Aphid transmission is undoubtedly the main route, but seed transmission has also been proposed (Schrijnwerkers et al. 1991). (Currier and Lockhart 1996). ...
Expansion and intensification of global trade in horticultural plants has increased the risk of spread of new alien pathogen species in the European Union (EU). Alien species of pathogenic viruses and viroids in horticultural plants have been introduced into Finland in infected plant material (plants, seedlings, cuttings, tubers, seeds). By 1997, about 30 virus species of horticultural plants had been detected in Finland. We aimed at compiling emerging new virus and viroid records during 1997-2010. Eight new viruses belonging to tospo-, potex-, poty-, tymo-, ilar- and allexiviruses were detected in horticultural plants: four occurred in greenhouse crops, two in vegetables and two in garden ornamentals outdoors. Five new findings of viroids were made in ornamental and vegetable greenhouse crops during 2008-2009. More rapid and accurate diagnostic methods have contributed to identifying new alien pathogens. Global trade seems to be the main reason for the introduction of the newest virus and viroid pathogens into Finland.
... Hosta virus X (HVX) belongs to the genus Potexvirus, in the family Alphaflexiviridae and is considered the most important pathogen that is capable of infecting the hosta plant. The host range of the virus is limited to various hosta species (Currier & Lockhart, 1996). Hosta virus X is transmitted by seeds, mechanical transmission and vegetative propagation (Lockhart & Currier, 1996; Ryu et al., 2006). ...
... The host range of the virus is limited to various hosta species (Currier & Lockhart, 1996). Hosta virus X is transmitted by seeds, mechanical transmission and vegetative propagation (Lockhart & Currier, 1996; Ryu et al., 2006). The potex-viruses are also known to survive and disseminate through water (Mehle & Ravnikar, 2012), but the transmission of Hosta virus X through water has not been demonstrated yet. ...
Abstract
Tobacco mosaic virus (TMV), Hosta virus X (HVX), Cucumber mosaic virus (CMV),
Tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INSV) are a few
of the major viruses that infect ornamental and nursery plants. These viruses
cause significant losses that impact growers and the ornamental industry. Often,
a single ornamental plant is co-infected by more than one virus, which makes
identification and discrimination of these viruses a difficult task, thus creating
delays and limiting regulatory measures for effective quarantine. The aim of this
study is to develop a sensitive, rapid, economic, and reliable multiplex Reverse
Transcription PCR (RT-PCR) for simultaneous detection and discrimination of
these five viruses. Specific PCR primers were designed using the consensus
sequences of corresponding capsid protein (CP) genes of HVX and CMV, the
nucleocapsid protein (NP) genes of TSWV and INSV, and themovement protein
(MP) and CP genes of TMV. The primers were validated in vitro using single and
multiplex RT-PCR assays. The detection limit of each primer set in multiplex
RT-PCR was 100 fg (TMV), 1 fg (HVX), 10 fg (CMV), 10 pg (TSWV) and 10 pg
(INSV). Forty-six infected nursery samples collected from different locations
in the USA were screened for virus infections using this multiplex RT-PCR.
The multiplex RT-PCR has a potential for its application in routine diagnostics,
quarantine, and epidemiological studies. The developed method is reliable,
sensitive, and economic for testing a wide range of ornamental and nursery
plants for detection of these viruses.
... Hosta is voor Nederland één van de belangrijkste producten voor de vaste plantenexport naar de VS en Canada. Sinds Hosta Virus X (HVX) in 1996 voor het eerst beschreven werd (Currier and Lockhart, 1996), is het in relatief korte tijd een bedreiging gaan vormen voor de Hosta-teelt. Al in 2000 toonde B. Lockhart aan dat minimaal 2/3 van het door hem geteste sortiment gevoelig bleek te zijn voor het virus (Lockhart, 2002). ...
... There is no evidence of biological vectors. Natural host range of HVX is restricted to hosta species (1). HVX causes wide variety of symptoms including mosaic or mottling, ringspots, irregular blotchy patches, enations, necrosis, stunting and dieback (2). ...
In September 2011, the leaf samples of hosta cultivar 'Sum and substance' were collected from the collection of Gryshko' National Botanical Garden in Kyiv. Th e leaves showed dark green streaking and puckering along the leaf veins. Transmission electron microscopy revealed the presence of filamentous viral particles 13 nm in diameter and 470-580 nm in length. Reverse transcription PCR (RT-PCR) analysis confirmed the presence of Hosta virus X (HVX). Th e sequencing of the complete genome revealed 99% identity to HVX- 37 and 97.5% identity to HVX-Kr. Notably, ORF4 initiation codon presented a non-conventional start codon (UUG) like it was previously identified in HVX-37.
... For antiserum production virions of RoYMV were extracted from infected leaf tissue of rose cv. Ballerina and purified by differential centrifugation and isopycnic density gradient centrifugation in Cs 2 SO 4 as described (Currier and Lockhart, 1996). An antiserum against purified virions was raised in a New Zealand White rabbit using a schedule of subcutaneous immunizations with purified virion antigen emulsified in an equal volume of Titermax Gold adjuvant (Sigma-Aldrich, St. Louis) (Mollov et al., 2007). ...
Four previously undescribed viruses infecting cultivated roses were identified and fully characterized in Minnesota. These four viruses were transmitted by grafting from infected to healthy roses and found to be the likely causal agents of the diseases with which they are associated. Viruses were provisionally named after the characteristic symptoms in infected plants as follows: Rose yellow vein virus (RYVV), Rose yellow mosaic virus (RoYMV), Rosa rugosa leaf distortion virus (RrLDV), and Rose yellow leaf virus (RYLV). Unlike the currently known viruses that affect rose, the ilarviruses and the nepoviruses, that only show symptoms and are detected early in the growing season, these new viruses exhibit symptoms throughout the season and can be detected readily during the entire year. Based on virion and genome properties it was determined that RYVV is a member of the family Caulimoviridae, RoYMV is a member of the family Potyviridae, and RrLDV and RYLV are members of the family Tombusviridae. Reliable diagnostic protocols were developed for each virus: PCR for RYVV; RT-PCR for RoYMV, RrLDV, and RYLV; and immunosorbent electron microscopy (ISEM) and indirect enzymelinked immunosorbent assay (ELISA) for RoYMV detection. © 2015, International Society for Horticultural Science. All rights reserved.
... HVX is the most economically important virus infecting hostas. First reported by Currier and Lockhart (1996), HVX-infected hostas have been found throughout the Midwestern U.S., in Canada, The Netherlands and South Korea. Infected hostas can be asymptomatic or exhibit a wide range of symptoms including stunting, enations, leaf twisting, distortion, ringspots, necrosis, and/or death Ryu et al., 2002;Lewandowski, 2008). ...
... HVX can be transmitted from infected to healthy plants by cutting practices used for propagation and breeding, as well as by means of HVX-contaminated soils (Ryu et al., 2006). HVX was first identified and described in Minnesota, USA in 1996 (Currier andLockhart, 1996). Since then, HVX was reported in hosta in other parts of the USA such as Kansas, Tennessee and Ohio (Kennelly et al., 2007;Fajolu et al., 2009;De la Torre, 2009) and other parts of the world such as Korea (Ryu et al., 2002). ...
The coat protein (CP) gene DNA sequences of nine isolates of Hosta virus X (HVX) from different regions of the Czech Republic were determined and compared with sequences available in GenBank. The sequences were almost uniform, the pairwise nucleotide identities among the Czech HVX isolates were 99-100%. The respective range was 98-100% when sequences from the GenBank were included. Therefore, phylogenetic analyses including Maximum parsimony and Bayesian analyses of either, DNA and deduced amino acid sequences, showed close relationship among isolates. Only the group of two isolates, HVXCR1 and HVXCR8 showed significant sequence divergence in phylogenetic trees. The HVXCR1-HVXCR8 group differs from the others by the substitution of glutamine (Q) by arginine (R). Moreover, these isolates showed different symptoms on infected hosta leaves - deformation on the leaves without a mosaic or mottling. This amino acid change may, therefore, have a biological significance. Keywords: Hosta virus X; coat protein; phylogenetic analysis.
... Virion purification, electron microscopy, capsid protein size measurement, and antiserum production. Virions were extracted and purified from infected coleus and N. benthamiana leaf tissue by differential centrifugation and isopycnic densitygradient centrifugation on Cs 2 SO 4 as described (6). Partially purified virion preparations were examined by TEM following negative staining with 2% (wt/vol) sodium phosphotungstate, pH 7.0, containing bacitracin (PTA) at 250 µg/ml. ...
A filamentous virus identified in coleus (Coleus x 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.
Weeds not only reduce crop yields and alter the functioning of ecosystems but also serve as alternate hosts for pests and plant pathogens or harbor vectors and vector-borne diseases. The role of weeds as reservoirs of viral pathogens and their impact on viral epidemiology and ecology is investigated in many parts of the world. The number of reports on viruses identified in weeds and new viruses discovered in cultivated and uncultivated plants is increasing globally. The most sensitive techniques used in screening and identification of viruses are nucleic acid-based detection methods. The metagenomic strategies are new approaches for analyzing viral populations in environmental samples through nucleic acid sequencing, which will make it possible to fill the gap in our knowledge of viruses in noncultivated plants. This review presents data on weeds as reservoirs of plant viruses and on current methods for studying pathogens.
Hosta virus X (HVX) is the most economically significant virus infecting hosta (Hosta spp.) plants worldwide, and has been reported from North America, Europe, Asia and Oceania. In May 2019, various viral-like disease symptoms were observed on hosta plants in a park in Harbin City in Northeast China, and infection by HVX was confirmed by small RNA sequencing, RT-PCR and electron microscopy. The infectivity of HVX on Hosta ensata, a native species in Northeast China, was confirmed by mechanical inoculation. We determined the complete genome sequence of an isolate of the virus, which revealed a high level of sequence similarity with other HVX genome sequences published to date. Phylogenetic analysis of HVX with other potexviruses based on the complete sequences revealed that all four HVX entries clustered to a single clade, which was most closely related to cassava common mosaic virus (CsCMV), hydrangea ringspot virus (HdRSV), plantago asiatica mosaic virus (PlAMV) and tulip virus X (TVX). Two potential recombination events were detected among the four HVX isolates. This work not only reports the complete genome sequence of an HVX isolate in Northeast China for the first time, but also suggests the need to prevent further spread of this virus in the region.
The one-step real-time turbidity loop-mediated isothermal amplification assay (RealAmp) was developed to detect Hosta virus X (HVX), the most devastating threat to hosta industry. The reaction was performed in a single tube at 63°C for 15 min, and real-time turbidimetry was used to monitor the amplification results. Specificity and sensitivity analyses demonstrated that this RealAmp method was sensitive as real-time TaqMan RT-PCR and about 100-fold higher than conventional RT-PCR with no cross-reaction with other viral pathogens. Field samples detection showed that HVX could be identified effectively with this method. Overall, this RealAmp assay for HVX detection was simple, specific, sensitive, convenient and time-saving and could assist in the quarantine measures for prevention and control of the disease caused by HVX.
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.
Icosahedral virus-like particles were isolated from Petunia hybrida cuttings with interveinal chlorotic mottling. The virus was transmitted by mechanical inoculation from infected to healthy P. hybrida, and was found to contain a bipartite RNA genome of 7.6 and 3.8 kilobases. Full genomic sequence was obtained by high-throughput sequencing combined with RACE amplification of the 5′-termini of RNAs 1 and 2, and reverse- transcription PCR amplification of the 3′-termini with oligo-dT and sequence specific primers. Based on particle morphology, genome organization, and phylogenetic analyses, it was concluded that the new virus is a member of the genus Nepovirus, subgroup A. This new virus causing a leaf mottling disease of petunia was provisionally named Petunia chlorotic mottle virus (PCMoV). © 2017, American Phytopathological Society. All rights reserved.
Hosta virus X (HVX) is the most damaging virus of hosta (Hosta spp.). By taking advantage of the conserved coat protein (CP) sequences of characterised isolates of HVX, a reliable and sensitive diagnostic assay, based on RT-PCR, was developed. The conserved, single Hind II recognition site within the CP sequences was also exploited for restriction fragment length polymorphism (RFLP)-based verification of the amplicons.The reliability of the assay was demonstrated by successful amplification of 30 HVX isolates from 20 cultivars of hosta.The effectiveness of the assay was demonstrated by detecting several distinct isolates of HVX in a mechanically-inoculated hosta cultivar containing a low virus titre. The assay was capable of detecting HVX in composite samples consisting of a single HVX-infected leaf disc, approx. 1 cm in diameter, combined with up to 200 virus-free leaf discs of similar size, which demonstrated its potential for large-scale screening. The sensitivity of the assay was not affected by genetic variation in the hosta cultivars or in the virus isolates.We conclude that RT-PCR/RFLP is reliable, sensitive, and efficient for large-scale screening of hosta for HVX infection.
A potexvirus was isolated from diseased hosta (Host a longipes) plants causing mosaic, mottle interveinal chlorosis symptoms between secondary veins, and leaf desiccation, identified as Hosta virus X (HYX-Kr) based on its biological, serological and molecular properties in this study. Infection rate of HVX in cultivated hostas was 48.4%, 21 out of 43 collected samples contained HVX. The virus was detected from seeds, and sprouts and seedlings. HVX was ascertained seed transmission of the virus from infected parent plant to progeny ones for breeding program of hosta plants. HVX was seed-transmitted on Hosta 'Blue Cadet'. Over 7.5% of seeds from HVX-infected hosta were HVX-contaminated surveyed in this study. The CP gene of HVX-U was amplified by RT-PCR and its nucleotide sequence was determined. The CPs of HVX-Kr and HVX-U had 100% and 98.9% identical amino acids and nucleotides, respectively. Variability of HVX was confirmed by sequences of CP gene of individual isolates from different hostas. Total nucleic acids extracted from leaf of virus-infected Hostas were used for detection of HVX by RT-PCR using the HVX-specific primers (HV UP:5722-5742 bp region of HVX-Kr strain /HV DN: 6428-6448 bp region of HVX-Kr strain). Overall similarities for the coat proteins are from 98.3% to 99.7% and from 98.2% to 100.0% identity with those of other HVX isolates at nucleotide and amino acid levels, respectively. This is the first report of molecular evidence supporting HVX as a distinct species of the genus Potexvirus and seed transmission of HVX.
Hosta virus X potexvirus is the most commonly occurring virus of hostas (Hosta spp.) in the USA, and can produce very damaging symptoms in some hosta cultivars. Fifty-seven hosta cultivars were evaluated for response to natural or experimental infection by HVX, and fell into three distinct categories. Susceptible cultivars developed pronounced symptoms, frequently resulting in complete leaf desiccation. Tolerant cultivars became infected but developed no visual symptoms. Immune cultivars were not infected by HVX. Management of HVX infection in hostas can be achieved by elimination of HVX-infected susceptible cultivars, ELISA indexing of tolerant cultivars, and using planting distances that minimize the possibility of me chanical spread of HVX between tolerant and susceptible cultivars.
Hostas ( Hosta spp.) are popular herbaceous perennial plants represented by over 7000 varieties, and widely cultivated due to their diversity in leaf shape and colour patterns, shade tolerance and pest resistance. In the Czech Republic,…
A putative Potexvirus was detected from bottle gourd (Lagenaria siceraria) showing mosaic and mottle symptoms in Myanmar in 2007. The virus was designated Lagenaria mild mosaic virus (LaMMoV) and was further characterized. In artificial inoculation tests, infectivity of LaMMoV was limited to two families: Chenopodiaceae and Cucurbitaceae. The host range of LaMMoV differs from those of the two cucurbit-infecting potexviruses, Alternanthera mosaic virus (AltMV) and Papaya mosaic virus (PapMV). Sequence analyses of LaMMoV showed that the C-terminal 3,859 nucleotides, excluding the poly-A tail, includes the C-terminal region of an RNA-dependent RNA polymerase (RdRp), a triple gene block (TUB), a coat protein (CP), and a 3' untranslated region (UTR), all of which are typical of potexviruses. Although LaMMoV is related closely to AltMV and PapMV, its nucleotide sequences differ from those of other previously reported potexviruses. Therefore, we report LaMMoV as a new species of the genus Potexvirus that occurs in the cucurbit bottle gourd.
Hosta (Hosta spp.) plants showing leaf deformation, puckering, and ink-bleed symptoms were collected in July 2012 from a park at Dongcheng district, Beijing, China. Three out of six samples tested positive for Hosta virus X (HVX) by immunostrip and double-antibody sandwich (DAS)-ELISA with HVX-specific serological reagents from Agdia Inc. (Elkhart, IN, USA). Filamentous viral particles were trapped and observed from the infected hosta leaf sap by immuno-serological electron microscopy (ISEM) (antibodies from Agdia). To confirm HVX infection, three ELISA-positive samples were analyzed by reverse transcription-PCR assay, using virus-specific primers HVXf (5′-ATCCGTTATCTACAGGGGACCAG-3′) and HVXr (5′-TAAGTTAGTGGAACGGTTAGCCCGAT-3′) that amplified a 1,067-bp fragment including the coat protein (CP) coding region. The CP nucleotide sequence comparisons showed 99% to 100% homology among the three isolates named HVXBJ4, HVXBJ5, and HVXBJ6 (GenBank Accession No. JX535292, JX535293, and JX535294) and with the HVX sequences previously reported in GenBank. HVX has been reported from the United States, Korea, the Netherlands, Poland, France, the Czech Republic, and New Zealand (1,2). To our knowledge, this is the first report of HVX infecting hosta plants in China. As an ornamental and medicinal plant, hosta has been cultivated in China for more than 2,000 years. The presence of HVX in Beijing is a potential threat to the landscape in the city. HVX can be spread by vegetative propagation material or mechanical contact (3). Hence, to cultivate HVX-free hosta and restrict the movement of HVX-infected hosta is vitally important in the future. HVX has become economically important in the world more recently. Globalization of trade in hosta plants has increased the risk of movement of HVX. The national plant protection organization should establish effective quarantine strategy and the growers take proper planting measures to avoid further spreading of this virus.
References: (1) S. Currier et al. Plant Dis. 80:1040, 1996. (2) M. H. Park et al. Arch. Virol. 148:2039, 2003. (3) K. H. Ryu et al. Acta Hortic. 722:91, 2006.
The purpose of the study was to evidence occurrence of Canna yellow mottle virus (CaYMV) and Canna yellow streak virus (CaYSV) in Canna spp. and Hosta virus X in Hosta spp. in the Czech Republic. Canna plants showing symptoms such as mottling and veinal streaking and Hosta plants showing symptoms such as mosaic, mottling and chlorosis were analyzed by PCR in the year 2010.
Systemic virus symptoms caused by a Potexvirus were observed on leaves of infected hosta (Hasta spp.) plants cultivated in Seoul, Korea. Symptoms on diseased hosta plants include mosaic, mottle, irregular blotchy patches, and chlorotic spots on or distortion of the leaves. No other viruses, such as Cucumber mosaic virus, Lily symptomless virus, or Potyvirus, were detected from the same plants by electron microscopy and by Western blot and RT-PCR analyses, indicating that they were singly infected by the potexvirus. The symptoms differed among cultivars and species of hosta, and affected the quality of plants for commercialization, as well as, plant growth and flowering of susceptible cultivars. Most of the cultivars and species investigated were susceptible to the virus, while some were not infected by the virus at all. Purified virus particles were of filamentous type with unaggregated forms 540 nm in length, which is a typical potexviral morphology. The virus consisted of a single-stranded RNA molecule of 6 kb long for genome and single component of coat protein (CP) about 27 kDa. The CP strongly reacted with the antiserum against Hosta vims X (HVX), suggesting that the virus is an isolate of HVX. This is the first report of the occurrence and identification of HVX from hosta plants in Korea.
Leaf mosaic and deformation symptoms were observed on hosta plants (Hosta spp.) in a nursery in Kihikihi in the North Island of New Zealand. The virus associated with these symptoms has been identified as Hosta virus X (HVX), using electron microscopy, mechanical transmission, ELISA and RT-PCR techniques. This is the first report of HVX in New Zealand although this virus is believed to have been present and widespread in the country for more than 10 years.
Hosta virus X (HVX) is a mechanically-spread Potexvirus that infects several species in the genus Hosta. The virus causes a variety of symptoms including color-streaking, mosaic, distortion, and necrosis, though some infected plants remain symptomless. To our knowledge, these are the first occurrences of HVX in Kansas.
Accepted for publication 16 April 2007. Published 26 September 2007.
Hosta virus X(HVX) is rapidly becoming a serious pathogen of commercially important hosta plants worldwide. We report here a biological and molecular characterization of a U.S. isolate of HVX, HVX-37. HVX-37 infectivity was tested in 21 hosta cultivars over three growth seasons, and three types of responses were defined based upon the ability of the virus to cause local and/or systemic infections. Four cultivars resistant to systemic HVX infection were identified. The full-length sequence of the HVX-37 genome was determined, the first complete sequence of a U.S. HVX isolate. Comparison with the previously sequenced HVX-Korea (Kr) genome revealed a high level of sequence similarity, as well as some differences. Notably, a 105 nucleotide long, near perfect direct repeat in the Kr isolate is absent in HVX-37. The accuracy of the HVX-37 genome sequence was confirmed by infectivity of in vitro transcripts synthesized from a full-length HVX-37 cDNA on N. benthamiana and hosta plants.
Accurate plant disease diagnoses and rapid detection and identification of plant pathogens are of utmost importance for controlling plant diseases and mitigating the economic losses they incur. Technological advances have increasingly simplified the tools available for the identification of pathogens to the extent that, in some cases, this can be done directly by growers and producers themselves. Commercially available immunoprinting kits and lateral flow devices (LFDs) for detection of selected plant pathogens are among the first tools of what can be considered grower-friendly pathogen monitoring methods. Research efforts, spurned on by point-of-care needs in the medical field, are paving the way for the further development of on-the-spot diagnostics and multiplex technologies in plant pathology. Grower-friendly methods need to be practical, robust, readily available, and cost-effective. Such methods are not restricted to on-the-spot testing but extend to laboratory services, which are sometimes more practicable for growers, extension agents, regulators, and other users of diagnostic tests.
The complete genome of Hosta Virus X (HVX), which is thought to be a distinct species of Potexvirus, was sequenced. Nucleotide sequences of HVX were compared with those of other members of the genus Potexvirus and phylogenetic tree was constructed. The range of identities of viral replicase open reading frame 1 (ORF1) between HVX and other potexviruses were 43.1%-55.1% and 35.9%-46.6% at the nucleotide and amino acid levels, respectively. Phylogenetic analysis was performed according to the amino acid sequence of the replicase to determine the position of HVX in the genus Potexvirus. Results from the phylogenetic analysis demonstrated that HVX was in the same group as Cassava common mosaic virus (CsCMV), Plantago asiatica mosaic virus (PlAMV), Tulip virus X (TVX), and Hydrangea ring spot virus (HdRSV). In particular, coat protein (CP) sequences among viruses from different Hosta cultivars were revealed to be less variable than those from different isolates of Potato virus X (PVX), a Potexvirus type species. In the present study, HVX was transmissible by seeds of the Hosta "Blue Cadet" cultivar. Moreover, HVX was detected in the embryo but not in the seed coat or endosperm of the seed.
Viruses are important constraints to the movement and propagation of plant germplasm, especially for vegetatively propagated crops such as banana and plantain. Their control relies primarily on the use of virus-free plant material, whose production and certification requires sensitive and reliable detection methods. An existing polyvalent degenerate oligonucleotide RT-PCR (PDO-RT-PCR) assay was adapted to the detection of Banana mild mosaic virus (BanMMV) and Banana virus X, two Flexiviridae infecting Musa spp. PDO inosine-containing primers were found to be well suited to the detection of BanMMV, despite its high molecular diversity, but not to that of the highly conserved BVX, for which species-specific primers were designed. Sampling and sample processing steps were optimized in order to avoid nucleic acid purification prior to the reverse transcription step. A polyclonal anti-BanMMV antiserum was raised and successfully used for the immunocapture (IC) of BanMMV viral particles from leaf extracts, leading to the development of a PDO-IC-RT-nested PCR assay. Although the anti-BanMMV antiserum could to some extent recognize BVX viral particles, direct binding (DB) was shown to be a more efficient method for processing BVX-infected samples and a PDO-DB-RT-nested PCR assay was developed for the detection of BVX from leaf extracts.
Apotexvirus, Hosta virus X (HVX-Kr), causing mosaic and mottle symptoms was isolated from hosta plants ( Hosta spp.) in Korea. The 3'-terminal 2,711 nucleotides excluding the poly (A) tail were determined and shown to include the partial viral replicase, triple gene block (TGB) 1 (26 kDa), TGB2 (13 kDa), TGB3 (8 kDa), and 23 kDa coat protein (CP) and the 3'-nontranslated region (NTR), typical of potexviruses. The CP gene of the type isolate of HVX (HVX-U) was amplified by RT-PCR and its nucleotide sequence was determined. The CPs of HVX-Kr and HVX-U had 100% and 98.9% identical amino acids and nucleotides, respectively. Most of the regions of the genome HVX had over 50% nucleotide identical to other sequenced potexviruses. This is the first report of sequence information of HVX and molecular evidence supporting the virus as a distinct species of the genus Potexvirus.
An efficient protocol for the purification of pea seed-borne mosaic potyvirus (PSbMV) particles was developed. This led to the purification of 10 PSbMV isolates by a single procedure. Virus aggregation during purification did not occur and consequently, high virus yield was consistently obtained. The virus thus purified was suitable for preparing viral genomic RNA, although conventional methods for RNA extraction resulted in RNA degradation. An alternative method was adopted which yielded reproducibly full length and infectious RNA. This was applied to three isolates of PSbMV and the RNA used to direct complementary DNA synthesis which in turn yielded nearly full length cDNA products.
This paper describes agarose gel electrophoresis and silver staining of denatured RNAs. Glyoxal- or formaldehyde-denatured RNAs are electrophoresed in an agarose gel cast on a plastic support using an inert, low conductivity buffer. Following electrophoresis, the gel is stained with a sensitive silver stain. The method produces sharp, well-resolved bands and yields accurate RNA size estimates. Because of its sensitivity and simplicity, it is suitable for routine laboratory use.