Complete nucleotide sequence of a potato isolate of strain group C of Potato virus Y from 1938

The complete genomic sequence of an isolate (PRI-509) of the C strain of Potato virus Y (PVYC), which was originally isolated from potato in 1938, was elucidated. The genomic RNA of PRI-509 consists of 9699 nucleotides, with the capacity to encode a polyprotein of 3061 amino acids with a molecular mass of 337 kDa

Mixed viral infection constrains the genome formula of multipartite cucumber mosaic virus

Many plant viruses have a multipartite organization, with multiple genome segments packaged into separate virus particles. The genome formula describes the relative frequencies of all viral genome segments, and previous work suggests rapid changes in these frequencies facilitate virus adaptation. Many studies have reported mixed viral infections in plants, often resulting in strong virus–virus interactions. Here, we tested whether mixed infections with tripartite alfalfa mosaic virus (AMV) and monopartite potato virus Y (PVY) affected the genome formula of the tripartite cucumber mosaic virus (CMV), our experimental model. We found that the CMV titer was reduced in mixed infections with its tripartite Bromoviridae relative AMV and in triple infections with both AMV and PVY, indicating notable virus–virus interactions. The variability of the CMV genome formula was significantly lower in mixed infections (CMV and AMV, CMV and PVY, and CMV and AMV and PVY) than in single infections (CMV only). These observations led to the surprising conclusion that mixed infections with two distinct viruses constrain the CMV genome formula. It remains unclear how common these effects are for different combinations of virus species and strains and what the underlying mechanisms are. We, therefore, extended a simulation model to consider three putative scenarios in which a second virus affected the genome formula. The simulation results also suggested that shifts in the genome formula occur, but may not be widespread due to the required conditions. One scenario modeled—co-infection exclusion through niche differentiation—was congruent with the experimental data, as this scenario led to reductions in genome formula variability and titer of the multipartite virus. Whereas previous studies highlighted host–species effects, our results indicate that the genome formula is also affected by mixed infections, suggesting that there is a broader set of environmental cues that affect the genome formula

Arabidopsis latent virus 1, a comovirus widely spread in Arabidopsis thaliana collections

Transcriptome studies of Illumina RNA-Seq datasets of different Arabidopsis thaliana natural accessions and T-DNA mutants revealed the presence of two virus-like RNA sequences which showed the typical two-segmented genome characteristics of a comovirus. This comovirus did not induce any visible symptoms in infected A. thaliana plants cultivated under standard laboratory conditions. Hence it was named Arabidopsis latent virus 1 (ArLV1). Virus infectivity in A. thaliana plants was confirmed by quantitative reverse transcription polymerase chain reaction, transmission electron microscopy and mechanical inoculation. Arabidopsis latent virus 1 can also mechanically infect Nicotiana benthamiana, causing distinct mosaic symptoms. A bioinformatics investigation of A. thaliana RNA-Seq repositories, including nearly 6500 Sequence Read Archives (SRAs) in the NCBI SRA database, revealed the presence of ArLV1 in 25% of all archived natural A. thaliana accessions and in 8.5% of all analyzed SRAs. Arabidopsis latent virus 1 could also be detected in A. thaliana plants collected from the wild. Arabidopsis latent virus 1 is highly seed-transmissible with up to 40% incidence on the progeny derived from infected A. thaliana plants. This has probably led to a worldwide distribution in the model plant A. thaliana with as yet unknown effects on plant performance in a substantial number of studies

Host range and symptomatology of Pepino mosaic virus strains occurring in Europe

Pepino mosaic virus (PepMV) has caused great concern in the greenhouse tomato industry after it was found causing a new disease in tomato in 1999. The objective of this paper is to investigate alternative hosts and compare important biological characteristics of the three PepMV strains occurring in Europe when tested under different environmental conditions. To this end we compared the infectivity and symptom development of three, well characterized isolates belonging to three different PepMV strains, EU-tom, Ch2 and US1, by inoculating them on tomato, possible alternative host plants in the family Solanaceae and selected test plants. The inoculation experiments were done in 10 countries from south to north in Europe. The importance of alternative hosts among the solanaceous crops and the usefulness of test plants in the biological characterization of PepMV isolates are discussed. Our data for the three strains tested at 10 different European locations with both international and local cultivars showed that eggplant is an alternative host of PepMV. Sweet pepper is not an important host of PepMV, but potato can be infected when the right isolate is matched with a specific cultivar. Nicotiana occidentalis 37B is a useful indicator plant for PepMV studies, since it reacts with a different symptomatology to each one of the PepMV strains.Ravnikar, M.; Blystad, D.; Van Der Vlugt, R.; Alfaro Fernández, AO.; Del Carmen Cordoba, M.; Bese, G.; Hristova, D.... (2015). Host range and symptomatology of Pepino mosaic virus strains occurring in Europe. European Journal of Plant Pathology. 143(1):43-56. doi:10.1007/s10658-015-0664-1S43561431Alfaro-Fernández, A., Córdoba-Sellés, M. C., Herrera-Vásquez, J. A., Cebrián, M. C., & Jordá, C. (2009). Transmission of Pepino mosaic virus by the fungal vector Olpidium virulentus. Journal of Phytopathology, 158, 217–226.Charmichael, D. J., Rey, M. E. C., Naidoo, S., Cook, G., & van Heerden, S. W. (2011). First report of Pepino mosaic virus infecting tomato in South Africa. Plant Disease, 95(6), 767.2.Córdoba, M. C., Martínez-Priego, L., & Jordá, C. (2004). New natural hosts of Pepino mosaic virus in Spain. Plant Disease, 88, 906.Córdoba-Sellés, M. C., García-Rández, A., Alfaro-Fernández, A., & Jordá-Gutiérrez, C. (2007). Seed transmission of pepino mosaic virus and efficacy of tomato seed disinfection treatments. Plant Disease, 91, 1250–1254.Efthimiou, K. E., Gatsios, A. P., Aretakis, K. C., Papayannis, L. C., & Katis, N. I. (2011). First report of Pepino mosaic virus infecting greenhouse cherry tomato in Greece. Plant Disease, 95(1), 78.2.Fakhro, A., von Bargen, S., Bandte, M., Büttner, C., Franken, P., & Schwarz, D. (2011). Susceptibility of different plant species and tomato cultivars to two isolates of Pepino mosaic virus. European Journal of Plant Pathology, 129, 579–590.Gómez, P., Sempere, R. N., Elena, S. F., & Aranda, M. A. (2009). Mixed infections of Pepino mosaic virus strains modulate the evolutionary dynamics of this emergent virus. Journal of Virology, 83, 12378–12387.Hanssen, I. M., Paeleman, A., Wittemans, L., Goen, K., Lievens, B., Bragard, C., Vanachter, A. C. R. C., & Thomma, B. P. H. J. (2008). Genetic characterization of Pepino mosaic virus isolates from Belgian greenhouse tomatoes reveals genetic recombination. European Journal of Plant Pathology, 121, 131–146.Hanssen, I. M., Paeleman, A., Vandewoestijne, E., Van Bergen, L., Bragard, C., Lievens, B., Vanachter, A. C. R. C., & Thomma, B. P. H. J. (2009). Pepino mosaic virus isolates and differential symptomatology in tomato. Plant Pathology, 58, 450–460.Hanssen, I. M., Mumford, R., Blystad, D.-G., Cortez, I., Hasiów-Jaroszewska, B., Hristova, D., Pagán, I., Pereira, A.-M., Peters, J., Pospieszny, H., Ravnikar, M., Stijger, I., Tomassoli, L., Varveri, C., van der Vlugt, R., & Nielsen, S. L. (2010). Seed transmission of Pepino mosaic virus in tomato. European Journal of Plant Pathology, 126, 145–152.Hasiów-Jaroszewska, B., Borodynko, N., Jackowiak, P., Figlerowicz, M., & Pospieszny, H. (2010a). Pepino mosaic virus – a pathogen of tomato crops in Poland: biology, evolution and diagnostics. Journal of Plant Protection Research, 50, 470–476.Hasiów-Jaroszewska, B., Jackowiak, P., Borodynko, N., Figlerowicz, M., & Pospieszny, H. (2010b). Quasispecies nature of Pepino mosaic virus and its evolutionary dynamics. Virus Genes, 41, 260–267.Jeffries, C. J. (1998). FAO/IPGRI technical guidelines for the safe movement of germplasm no. 19. Potato. Food and agriculture organization of the United Nations, Rome/International Plant Genetic Resources Institute, Rome pp 177Jones, R. A. C., Koenig, R., & Lesemann, D. E. (1980). Pepino mosaic virus, a new potexvirus from pepino (Solanum muricatum). Annals of Applied Biology, 94, 61–68.Jordá, C., Lázaro Pérez, A., & Martínez Culebras, P. (2001). First report of Pepino mosaic virus on natural hosts. Plant Disease, 85, 1292.King, A. M. Q., Adams, M. J., Carstens, E. B., Lefkowitz, E. J., (eds). (2012). potexvirus, pp 912–915, in virus taxonomy, classification and nomenclature of viruses; ninth report of the international committee on taxonomy of viruses (p 1327) London, UK: Elsevier Academic PressLing, K.-S., & Zhang, W. (2011). First report of Pepino mosaic virus infecting tomato in Mexico. Plant Disease, 95(8), 1035.Martin, J., & Mousserion, C. (2002). Potato varieties which are sensitive to the tomato strains of Pepino mosaic virus (PepMV). Phytoma Défence Végétaux, 552, 26–28.Mehle, N., Gutierrez-Aguirre, I., Prezelj, N., Delić, D., Vidic, U., & Ravnikar, M. (2014). Survival and transmission of potato virus Y, pepino mosaic virus, and potato spindle tuber viroid in water. Applied and Environmental Microbiology, 80(4), 1455–1462.Moreno-Pérez, M. G., Pagán, I., Aragón-Caballero, L., Cáceres, F., Aurora Fraile, A., & García-Arenal, F. (2014). Ecological and genetic determinants of Pepino mosaic virus emergence. Journal of Virology, 88(6), 3359–3368.Noël, P., Hance, T., & Bragard, C. (2014). Transmission of the pepino mosaic virus by whitefly. European Journal of Plant Pathology, 138, 23–27.Pagan, I., Cordoba-Selles, M. D., Martinez-Priego, L., Fraile, A., Malpica, J. M., Jorda, C., & Garcia-Arenal, F. (2006). Genetic structure of the population of pepino mosaic virus infecting tomato crops in Spain. Phytopathology, 96, 274–279.Papayiannis, L. C., Kokkinos, C. D., & Alfaro-Fernández, A. (2012). Detection, characterization and host range studies of Pepino mosaic virus in Cyprus. European Journal of Plant Pathology, 132, 1–7.Pospieszny, H., Haslow, B., & Borodynko, N. (2008). Characterization of two Polish isolates of Pepino mosaic virus. European Journal of Plant Pathology, 122, 443–445.Salomone, A., & Roggero, P. (2002). Host range, seed transmission and detection by ELISA and lateral flow of an Italian isolate of Pepino mosaic virus. Journal of Plant Pathology, 84, 65–68.Samson, R. G., Allen, T. C., & Whitworth, J. L. (1993). Evaluation of direct tissue blotting to detect potato viruses. American Potato Journal, 70, 257–265.Schwarz, D., Beuch, U., Bandte, M., Fakhro, A., Büttner, C., & Obermeier, C. (2010). Spread and interaction of pepino mosaic virus (PepMV) and pythium aphanidermatum in a closed nutrient solution recirculation system: effects on tomato growth and yield. Plant Pathology, 59(3), 443–452.Shipp, J. L., Buitenhuis, R., Stobbs, L., Wang, K., Kim, W. S., & Ferguson, G. (2008). Vectoring of pepino mosaic virus by bumble-bees in tomato greenhouses. Annals of Applied Biology, 153, 149–155.Van der Vlugt, R. A. A. (2009). Pepino mosaic virus (review). Hellenic Plant Protection Journal, 2, 47–56.Van der Vlugt, R. A. A., & Stijger, C. C. M. M. (2008). Pepino mosaic virus. In B. W. J. Mahy & M. H. V. Van Regenmortel (Eds.), Encyclopedia of virology (5th ed., pp. 103–108). Wageningen: Oxford Elsevier.Van der Vlugt, R. A. A., Stijger, C. C. M. M., Verhoeven, J. T. J., & Lesemann, D.-E. (2000). First report of Pepino mosaic virus on tomato. Plant Disease, 84, 103.Van der Vlugt, R. A. A., Cuperus, C., Vink, J., Stijger, I. C. M. M., Lesemann, D.-E., Verhoeven, J. T. J., & Roenhorst, J. W. (2002). Identification and characterization of Pepino mosaic potexvirus in tomato. Bulletin EPPO/EPPO Bulletin, 32, 503–508.Verchot-Lubicz, J., Chang-Ming, Y., & Bamunusinghe, D. (2007). Molecular biology of potexviruses: recent advances. Journal of General Virology, 88(6), 1643–1655.Verhoeven, J. T. H. J., van der Vlugt, R., & Roenhorst, J. W. (2003). High similarity between tomato isolates of pepino mosaic virus suggests a common origin. European Journal of Plant Pathology, 109, 419–425.Werkman, A.W., & Sansford, C.E. (2010). Pest risk analysis for pepino mosaic virus for the EU. Deliverable Report 4.3. EU Sixth Framework project PEPEIRA. http:// www.pepeira.com .Wright, D., & Mumford, R. (1999). Pepino mosaic potexvirus (PepMV): first records in tomato in the United Kingdom. Plant disease notice (89th ed.). York, UK: Central Science Laboratory

Evaluation of sequencing and PCR-based methods for the quantification of the viral genome formula

Viruses show great diversity in their genome organization. Multipartite viruses package their genome segments into separate particles, most or all of which are required to initiate infection in the host cell. The benefits of such seemingly inefficient genome organization are not well understood. One hypothesised benefit of multipartition is that it allows for flexible changes in gene expression by altering the frequency of each genome segment in different environments, such as encountering different host species. The ratio of the frequency of segments is termed the genome formula (GF). Thus far, formal studies quantifying the GF have been performed for well-characterised virus-host systems in experimental settings using RT-qPCR. However, to understand GF variation in natural populations or novel virus-host systems, a comparison of several methods for GF estimation including high-throughput sequencing (HTS) based methods is needed. Currently, it is unclear how HTS-methods compare a golden standard, such as RT-qPCR. Here we show a comparison of multiple GF quantification methods (RT-qPCR, RT-digital PCR, Illumina RNAseq and Nanopore direct RNA sequencing) using three host plants (Nicotiana tabacum, Nicotiana benthamiana, and Chenopodium quinoa) infected with cucumber mosaic virus (CMV), a tripartite RNA virus. Our results show that all methods give roughly similar results, though there is a significant method effect on genome formula estimates. While the RT-qPCR and RT-dPCR GF estimates are congruent, the GF estimates from HTS methods deviate from those found with PCR. Our findings emphasize the need to tailor the GF quantification method to the experimental aim, and highlight that it may not be possible to compare HTS and PCR-based methods directly. The difference in results between PCR-based methods and HTS highlights that the choice of quantification technique is not trivial

Evaluation of sequencing and PCR-based methods for the quantification of the viral genome formula

Viruses show great diversity in their genome organization. Multipartite viruses package their genome segments into separate particles, most or all of which are required to initiate infection in the host cell. The benefits of such seemingly inefficient genome organization are not well understood. One hypothesised benefit of multipartition is that it allows for flexible changes in gene expression by altering the frequency of each genome segment in different environments, such as encountering different host species. The ratio of the frequency of segments is termed the genome formula (GF). Thus far, formal studies quantifying the GF have been performed for well-characterised virus-host systems in experimental settings using RT-qPCR. However, to understand GF variation in natural populations or novel virus-host systems, a comparison of several methods for GF estimation including high-throughput sequencing (HTS) based methods is needed. Currently, it is unclear how HTS-methods compare a golden standard, such as RT-qPCR. Here we show a comparison of multiple GF quantification methods (RT-qPCR, RT-digital PCR, Illumina RNAseq and Nanopore direct RNA sequencing) using three host plants (Nicotiana tabacum, Nicotiana benthamiana, and Chenopodium quinoa) infected with cucumber mosaic virus (CMV), a tripartite RNA virus. Our results show that all methods give roughly similar results, though there is a significant method effect on genome formula estimates. While the RT-qPCR and RT-dPCR GF estimates are congruent, the GF estimates from HTS methods deviate from those found with PCR. Our findings emphasize the need to tailor the GF quantification method to the experimental aim, and highlight that it may not be possible to compare HTS and PCR-based methods directly. The difference in results between PCR-based methods and HTS highlights that the choice of quantification technique is not trivial

List of criteria the reference materials have to meet for use in validation studies

A list of general minimum criteria was developed to be used in preparation of reference materials to be used in interlaboratory testing, including validations through test performance studies. The list was based on previously identified criteria in standards including ISO standards, EPPO guidelines, deliverables of relevant projects, related fields, and own experience of project partners. Several additional criteria were proposed: ‘availability’, ‘purity’ and ‘commutability’. These criteria result from a series of discussions, taking into account previous work and relevant international standards. Where relevant, each criterion was first defined as a series of levels from the highest to lowest ranking with the lowest ranking considered to be the minimum. Depending on the intended use, the reference material may need to fulfil higher levels of selected criteria or some criteria may not be relevant at all. The criteria were tested by the organizers of the TPS in round 1 of validation within VALITEST project which include bacteria, viruses, nematodes and fungi. The systematic and structured approach of describing RMs was found to be useful in promoting transparent descriptions of the RMs used and comparability of TPSs, as well as a step toward implementing FAIR data principles. The criteria defined here are applicable, potentially with minor modification, beyond the scope of this deliverable and project to other pests and other uses of RM

Development of draft Standard Operating Procedures (SOPs) available for the production of the reference materials identified in task 3.1

A general standard operating procedure (SOP) for the production of reference material (RM) for use in plant health diagnostics was developed. The general SOP was designed based on (limited) information on existing SOPs and guidelines available with the consortium partners. The general SOP describes the different steps required in the production process, ranging from the different possible sources of the reference material, tests to confirm its identity, possibly required multiplication steps to the actual production process. For each step in the process, criteria and critical points are identified. The criteria that reference material has to meet, and their minimum required levels as identified and described in Deliverable 3.1 of WP3 form an import basis of the final production process

Predictions of the number of isolates of each pospiviroid species that will be detected using universal and species-specific assays of the Luminex MagPlex-TAG pospiviroid array.

<p>Predictions of the number of isolates of each pospiviroid species that will be detected using universal and species-specific assays of the Luminex MagPlex-TAG pospiviroid array.</p