Torradovirus
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Torradoviruses are a newly emerging group of plant viruses in the family Secoviridae. They include Tomato torrado virus, Tomato marchitez virus, Squash chlorotic leaf spot virus, Lettuce necrotic leaf curl virus, and Carrot torrado virus 1. Torradoviruses are transmitted by whiteflies and aphids and can be seed-borne. They infect crops like tomatoes, peppers, lettuce, and carrots. Detection methods include RT-PCR, ELISA, and next-generation sequencing. Recent surveys found infections of Lettuce necrotic leaf curl virus, Carrot torrado virus 1, and a cassava torrado-like virus, demonstrating their relevance in the field
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Torradovirus
- 1. Seminar on Torradovirus Ms. D. Anupriya, M.Sc.(Ag.) II Year Department of Plant Pathology Faculty of Agriculture Annamalai University, India E-mail: anupathologist@gmail.com
- 2. Introduction Taxonomic position of torradoviruses Group: Group IV (+)ssRNA Order: Picornavirales Family: Secoviridae Genus: Torradovirus Member species: Tomato torrado virus (ToTV) Tomato marchitez virus (ToMarV) Squash chlorotic leaf spot virus (SCLSV) Lettuce necrotic leaf curl virus (LNLCV) Carrot torrado virus 1 (CaTV1) Motherwort yellow mottle virus (MYMoV)
- 3. Related, unclassified viruses Tomato chocolate virus (ToChV) Tomato chocolate spot virus (ToChSV) Tomato necrotic dwarf virus (ToNDV) General characteristics of torradoviruses Epidemiology of torradoviruses Torradovirus host range Vector transmission Seed transmission Detection and Identification of torradoviruses Relevance of torradovirus infections in the field Conclusion
- 4. ICTV reported that the genus Torradovirus, a group of newly emerging plant viruses Torrado: derived from Tomato torrado virus (ToTV), the type species of the Torradovirus genus. In Spanish, torrado means toasted to refer to the severe necrosis (burnt-like phenotype) observed in the disease induced by ToTV. Thompson et al. (2017)
- 5. TAXONOMIC POSITION OF TORRADOVIRUSES Thompson et al. (2017)
- 6. Virus Taxonomy: The Classification and Nomenclature of Viruses The Online (10th) Report of the ICTV
- 7. Torradovirus Virus classification Group: Group IV (+)ssRNA Order: Picornavirales Family: Secoviridae Genus: Torradovirus Type Species •Tomato torrado virus
- 8. Species: Carrot torrado virus 1 (CaTV1) Species: Lettuce necrotic leaf curl virus (LNLCV) Species: Motherwort yellow mottle virus (MYMoV) Species: Squash chlorotic leaf spot virus (SCLSV) Species: Tomato marchitez virus (ToMarV) Species: Tomato torrado virus (ToTV) Member Species
- 9. Thompson et al. (2017)
- 10. Verbeek et al., 2007
- 11. Verbeek et al., 2008
- 12. Verbeek et al., 2014
- 13. Lecoq et al., 2016
- 14. Verbeek et al., 2014
- 15. Adams et al., 2014
- 16. Seo et al., 2014
- 17. Related, Unclassified Viruses Tomato chocolate virus (ToChV) Tomato chocolate spot virus (ToChSV) Tomato necrotic dwarf virus (ToNDV)
- 18. Batuman et al., 2010
- 20. GENERAL CHARACTERISTICS OF TORRADOVIRUSES
- 21. Alfaro-Fernandez et al., 2007
- 29. van der Vlugt et al., 2015
- 38. Torradovirus host range ToTV natural infection on tomato and also systemically infects eggplant (cv. Black Beauty) and pepper (cv. Italian Long Sweet) (Amari et al., 2008). ToNDV can also infect eggplant, pepper and tomatillo (Physalis philadelphica) (Larsen et al., 2009)
- 39. Vector transmission Torradoviruses (ToTV, ToMarV, SCLSV and ToChV) are transmitted by three whitefly species in a semi-persistent manner, Trialeurodes vaporariorum, Bemisia tabaci and Trialeurodes abutilonea (Verbeek et al., 2014; Lecoq et al., 2016). Carrot torrado virus 1 was demonstrated to be transmitted by three different species of aphids (Rozado-Aguirre et al., 2016).
- 46. Seed transmission (Wintermantel and Hladky, 2013) (Pospieszny et al., 2014) Tomato torrado virusTomato necrotic dwarf virus
- 47. Detection and Identification of torradoviruses RNA-based (RT-PCR) DAS-ELISA (Pospieszny et al., 2010) Hybridization with dioxigenin-labeled RNA-riboprobes (Da Silva et al., 2014) Primer pair Torrado-1F/Torrado-1R (designed on RNA1 sequences) Primer pair Torrado-2F/Torrado-2R (designed on RNA2) (Carvajal-Yepes et al., 2014) Next-generation sequencing (NGS) (Verbeek et al., 2014)
- 48. Relevance of torradovirus infections in the field Lettuce necrotic leaf curl virus isolate was found in 2013 in lettuce plants with typical symptoms subjected for analysis at the Dutch Plant Protection Service (Verbeek et al., 2014). During 2014, field surveillance was carried out for Carrot torrado virus 1 in the North of England (Fox et al., 2014). Carrot torrado virus 1 was detected in 14–25% of plants tested. In a recent survey on cassava viruses in Colombia, >50% of plants collected in the North Coast region during 2014 were infected with cassava torrado-like virus (Cuellar et al., 2014).
Editor's Notes
- Torradovirus is a genus of viruses in the order Picornavirales, in the family Secoviridae. Plants serve as natural hosts. There are currently six species in this genus.
- Secoviridae
- Tomato torrado virus infection on tomato leaves with necrotic spots surrounded by light green or yellow area beginning at the base of a leaflet.
- Symptoms of Tomato marchitez virus in tomato (Solanum lycopersicum)
- Tomato marchitez virus in tomato fruits symptoms are necrotic rings and patches and Electron microscope image of the virus.
- Symptoms of squash chlorotic leaf spot virus infection (a) in the original squash plant and (b) after mechanical inoculation to zucchini squash. (c) Virus particles observed in a leaf-dip preparation of an infected zucchini squash
- Lettuce necrotic leaf curl virus, disease symptoms observed in lettuce, comprising severe necrosis and leaf curling.
- Carrot torrado virus 1 (a) Cross section of carrot root showing internal necrosis around the root core. (b) Internal necrosis of carrot root along the root core. (c) External necrosis of the root tip. (d) Unaffected carrot
- Motherwort yellow mottle virus infected plants showing conspicuous virus-like symptoms, i.e., yellow mottle, mild mosaic and stunting.
- Tomato chocolate spot disease: symptoms similar to torrado disease, and locally known as mancha de chocolate (or chocolate spot), was observed in Guatemala.
- Symptoms and transmission characteristics of Tomato necrotic dwarf virus resemble those of other members of the emerging genus, Torradovirus.
- Torradoviruses possess small spherical virions, approximately 30 nm in diameter and have a bipartite genome and three capsid proteins 23, 26, and 35 kDa. Two single-stranded positive-sense RNA molecules RNA1 and RNA2.
- Electron micrograph of purified particles of Tomato torrado virus
- Table 1. Lengths in nucleotides (and in amino acids in parentheses for the respective encoded proteins) of RNA1 and RNA2 and their different regions of the recognized and tentative torradoviruses
- Figure 1. Genomic organization of torradoviruses
- Similarity plots of the three open-reading frames (ORF) of eight torradoviruses are shown in Figure 2.
- Levels of amino acid (aa) identity between the different torradoviruses in the 3C-like proteinase RNA–dependent RNA polymerase (Pro-Pol) region of RNA1-ORF1 are showed in Table 2.
- Overall levels of amino acid identity between the different torradoviruses in the 3C-like proteinase RNA–dependent RNA polymerase (Pro-Pol) region of ORF2 on RNA2 are showed in Table 3.
- Overall levels of amino acid identity between the different torradoviruses in the coat-protein domain of ORF2 on RNA2 are showed in Table 4.
- Overall levels of amino acid identity between the different torradoviruses in their movement-protein regions on RNA2-ORF2 are showed in Table 5.
- Figure 3. Unrooted neighbour-joining tree of selected members of the order Picornavirales based on the amino acid sequences of the conserved domains between the CG motif of the 3C-like proteinase and the GDD motif of the polymerase (Pro-Pol region). The alignment was produced by the program T-Coffee (Di Tommaso et al., 2011) and the tree was generated using CLUSTALX (Thompson et al., 2017).
- Figure 4. The amino acid sequence in the likely cleavage region between the movement protein and largest coat protein (Vp35) of the tomato-infecting torradoviruses, showing the conserved VxxLxxQ/RD proteinase recognition motif (boxed).
- Table 6. BLAST results obtained for the ORF1-RNA2 domains of different torradoviruses.
- Overall levels of amino acid identity between the different torradoviruses in their hypothetical protein regions on RNA2-ORF1 are showed in Table 7.
- Figure 5. An overall alignment of the amino acid residues encoded by ORF1 on RNA2 of the torradoviruses
- Figure 6. Schematic presentation indicating the locations of the conserved regions (CR-A shown in blue; CR-B in red) in the 3_ untranslated regions (UTRs), aligned at their 3_ termini, of RNA1 and RNA2 of the different tomato-infecting torradoviruses.
- Table 8. A comparison of the lengths in nucleotides [excluding the poly-(A) tail] and percentages of sequence identity of the variable regions and common regions in the 3 untranslated regions (3 UTRs) of RNA1 and RNA2 of the recognized and tentative torradoviruses.
- Figure 7. Highly conserved stem-loop structures in the 5_ region of the 3_ UTR of RNA2 of ToMarV as predicted by PFold. Although variable in sequence, the structures shown are highly conserved among all 3_ UTRs of TI torradoviruses.
- Trialeurodes vaporariorum Westwood, 1856, commonly known as the glasshouse whitefly
- Glasshouse whitefly larval stage
- Trialeurodes abutiloneus or the banded-wing whitefly first described by Haldeman in 1850.
- Silverleaf whitefly (Bemisia tabaci)
- Silverleaf whitefly (Bemisia tabaci)
- Aphids, Melanaphis sacchari