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Abstract
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.
... Long-distance dissemination is through movement of infected bulbs, tubers, and vegetative cuttings (Martelli et al., 2007). Seed transmission has been reported for several potexviruses species including Hosta virus X (HVX) (Ryu et al., 2006;Martelli et al., 2007). ...
... Hosta virus X (HVX) is a recently discovered potexvirus that causes economic losses to hosta growers and producers. It is transmitted by contaminated cutting tools, vegetative propagation and is seed transmitted (Ryu et al., 2006). The natural host range of HVX is restricted to hostas, but N. benthamiana Domin. ...
... In the Czech Republic, hostas are grown as outdoor ornamental plants. Over four viruses in hostas have been reported in the world, but Hosta virus X (HVX) is the most economically significant virus (Ryu et al., 2006). Leaves infected with HVX show symptoms, which include mosaic, mottling, irregular blotchy patches, chlorotic spots and distortion (Ryu et al., 2002). ...
... Infected plants often exhibit reduced growth and dieback. 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). ...
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.
... The host range of the virus is limited to various hosta species . Hosta virus X is transmitted by seeds, mechanical transmission and vegetative propagation 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. ...
... The host range of the virus is limited to various hosta species . Hosta virus X is transmitted by seeds, mechanical transmission and vegetative propagation 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.
... 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]. ...
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.
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.
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.
The methods for detecting seed-transmitted virus infection should be rapid, reliable and sensitive besides being simple to achieve results. This has been a challenge since the advent of the discipline of plant virology over 100 years ago, and a great variety of methods have been developed since that time. Based on biological, serological and molecular tests, the virus and viroid diseases are diagnosed. In biological tests, a close and careful observation on the seed morphology in certain cases gives a tentative indication of the presence of virus (es). Grow-out test also helps in seed-borne virus diagnosis. Among serological tests Ouchterlony, ELISA and its variants, dot-immunobinding assay, TBIA, and Immunosorbent electron microscopy are widely used for virus detection. Among antibody-based detections, and Polymerase chain reaction (PCR) and its variants, (real-time PCR, RT-PCR, IC-PCR, IC-RT-PCR, multiplex PCR), are extensively practice. Protocols have been implemented in the field using portable real-time PCR machines for same-day, on-site results; cDNA probes which are labelled with radioactive markers or nonradioactive markers are used for diagnosis of seed-borne virus and viroid diseases. Array technology has revolutionised the world of viral diagnosis because of its efficiency in screening a large volume of infected seed samples in a single array plate or reaction.
Seeds provide an efficient means in disseminating plant virus and viroid diseases. The success of modern agriculture depends on pathogen free seed with high yielding character and in turn disease management. There is a serious scientific concern about the transmission of plant viruses sexually through seed and asexually through plant propagules. The present book provides the latest information along with the total list of seed transmitted virus and viroid diseases at global level including, the yield losses, diagnostic techniques, mechanism of seed transmission, epidemiology and virus disease management aspects. Additional information is also provided on the transmission of plant virus and virus-like diseases through vegetative propagules. It is also well known that seed transmitted viruses are introduced into new countries and continents during large-scale traffic movements through infected germplasm and plant propogules. The latest diagnostic molecular techniques in different virus-host combinations along with disease management measures have been included. The book shall be a good reference source and also a text book to the research scientists, teachers, students of plant pathology, agriculture, horticulture, life sciences, green house managers, professional entrepreneurs, persons involved in quarantines and seed companies. This book has several important features of seed transmitted virus diseases and is a good informative source and thus deserves a place in almost all university libraries, seed companies and research organizations.
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,…
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.
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 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.
Four viruses, hosta virus X potexvirus, tomato ringspot nepovirus, impatiens necrotic spot tospovirus and a tobravirus were identified in hostas (Hosta spp.) in the USA. Three unidentified isometric viruses were also found in hostas. Hosta virus X, a previously undescribed potexvirus, was the most frequently occurring virus in hostas, whose response to infection by this virus varied from immunity to severe mosaic and leaf desiccation. Tomato ringspot virus infection in hostas was associated with leaf mottling and chlorosis. Impatiens necrotic spot virus caused primary foliar lesions followed by latent infection. The tobravirus occurring in hosta was related serologically to both pea early-browning and tobacco rattle viruses, but was unusual in not being transmitted by mechanical inoculation to Nicotiana benthamiana or to N. clevelandii. Three unidentified isometric viruses, detected by electron microscopy and ds RNA analysis, were found in hostas with chlorotic ringspots, veinal necrosis and interveinal chlorosis. This is the first report identifying viruses in hostas in the USA.
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.
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.
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.