Search

Inundatie of biofertigatie helpen niet tegen TVX. De virussen PlAMV en TVX verspreiden zich onder meer via onkruid, groenbemsters en grond. Wageningen Universiteit, Vertify en BKD zoeken in de PPS ‘Op weg naar virusvrij en afzetgericht telen’ hoe potexvirussen zich in het veld verspreiden. Virusvrij starten en onkruidvrij telen zijn essentieel, blijkt uit de PPS.

Cross-protectie is het fenomeen dat zwakke isolaten van een bepaald plantenvirus een plant kunnen beschermen tegen schade die worden veroorzaakt als een agressievere variant van dat zelfde virus later de plant infecteert. In dit rapport worden voor- en nadelen en aandachtspunten voor inzet van cross-protectie, gebaseerd op de literatuur, naar voren gebracht, maar ook een aantal voorwaarden aangedragen voor het produceren en inzetten van zulke zwakke virus-isolaten. Naar aanleiding van bovenstaande aandachtspunten zal worden ingegaan op de recente vraag vanuit de praktijk naar zwakke isolaten voor het komkommerbontvirus en het tomato brown rugose fruit virus. Voor deze beide virussen zijn op dit moment geen zwakke isolaten beschikbaar om in te zetten voor cross- protectie. Algemeen kan geconcludeerd worden dat de inzet van zwakke virusisolaten (mits beschikbaar) om de schade door meer ‘agressieve’ isolaten of stammen van een virus te verminderen slechts toepasbaar is voor specifieke virusziekten in bepaalde gewassen en onder bepaalde omstandigheden. Hiervoor worden in dit rapport een aantal aandachtspunten gegeven. De inzet van zwakke virusisolaten voor cross-protectie is pas aanvaardbaar wanneer er geen schade kan optreden voor het gewas zelf of andere gewassen, als er geen resistenties tegen het schadelijke virus beschikbaar zijn in het te behandelen gewas of als andere teeltmaatregelen, en dan met name hygiëne, om uiteenlopende redenen geen effect (meer) hebben.

Bladluizen verspreiden TBV en LMoV razendsnel binnen een partij tulp en lelie. Deze potyvirussen zijn nader onderzocht in de PPS Op weg naar virusvrij en afzetgericht telen. Nagegaan is of er alternatieven zijn voor glyfosaat en of bladluizen ook virus kunnen opnemen uit gekopte tulpenbloemen. Dat blijktzo te zijn. In dit eerste deel van een serie van drie artikelen over deze PPS gaat het over de overdracht van potyvirussen.

To obtain insight into the sequence diversity of strawberry latent ringspot virus (SLRSV), isolates from collections and diagnostic samples were sequenced by high-throughput sequencing. For five SLRSV isolates, the complete genome sequences were determined, and for 18 other isolates nearly complete genome sequences were determined. The sequence data were analysed in relation to sequences of SLRSV and related virus isolates available in the NCBI GenBank database. The genome sequences were annotated, and sequences of the protease-polymerase (Pro-Pol) region and coat proteins (CPs) (large and small CP together) were used for phylogenetic analysis. The amino acid sequences of the Pro-Pol region were very similar, whereas the nucleotide sequences of this region were more variable. The amino acid sequences of the CPs were less similar, which was corroborated by the results of a serological comparison performed using antisera raised against different isolates of SLRSV. Based on these results, we propose that SLRSV and related unassigned viruses be assigned to a new genus within the family Secoviridae, named “Stralarivirus”. Based on the phylogenetic analysis, this genus should include at least three viruses, i.e., SLRSV-A, SLRSV-B and lychnis mottle virus. The newly generated sequence data provide a basis for designing molecular tests to screen for SLRSV.

De roep om goede beheersingsstrategieën wordt na recente problemen met plantenvirussen steeds luider. Eén van die strategieën is het toepassen van een zwak virusisolaat dat de plant beschermt tegen de schade veroorzaakt door sterkere virusisolaten van dat bepaalde virus, ook wel ‘vaccinatie’ of ‘cross-protectie’ genoemd. In dit artikel een overzicht van wat dat nu precies is, een aantal voorbeelden en de voor- en nadelen van toepassing van cross-protectie.

Plantenvirussen zijn zeer kleine ziekteverwekkers. Eigenlijk zijn het kleine pakketjes met genetische informatie, een stukje RNA of DNA met een eiwitmantel eromheen. Viroïden zijn nog kleiner, omdat ze geen eiwitmantel bezitten en alleen uit RNA bestaan. Virussen en viroïden kunnen zich alleen vermenigvuldigen in een cel van hun gastheer en daarbij zetten ze zijn huishouding naar hun hand.

Dringend alternatieven nodig voor de beheersing van vergelingsziekte in de suikerbietenteelt. De ziekte kan de opbrengst ernstig schaden.

A total of 21 okra (Abelmoschus escuentus L. Moench) genotypes were screened for their reactions against okra mosaic disease (OMD) and flea beetles (Podagrica species) infestations in field trials which were conducted from May to October, 2015 (wet season) and November 2015 to March 2016 (dryseason), in order to identify sources of resistance and or tolerance. The trials were laid out in a randomised complete block design (RCBD) with four replications. Field resistance in the genotypes was assessed at 2, 6 and 10 weeks after planting using a 0 to 5 visual scale based on disease symptoms(where 1 denotes no symptom and 5, very severe symptom). Enzyme linked immunosorbent assay (ELISA) was performed to detect the presence of Okra mosaic virus (OkMV) in the okra genotypes.Populations of the flea beetle (Podagrica spp.), the vector of OkMV, and the associated leaf and fruit damage were also assessed. All the okra genotypes exhibited a varying range of disease symptoms and the flea beetle infestations, and lacked immunity. Genotypes GH2052, GH2063, GH2026, GH3760,GH5302, GH5332, GH5793, GH6105 and UCCC6 exhibited mild symptoms of OMD, and were less susceptible to flea beetle infestation and associated leaf damage during both seasons. Using ELISA, OkMV was detected in all the 21 genotypes. The mean number of fruits per plant and the mean fruit yield (t ha-1) differed significantly (P

New diagnostic and rapid ‘nextgeneration sequencing’ methods facilitate thediscovery of new plant viruses. However, virus detection or elucidation of thesequence of its dna/rna is no guarantee for understanding its epidemiology.In order to develop effective control measures in field crops or in greenhouses,knowledge of how viruses move from one plant to another is essential.

The plant virus genus Torradovirus was created to contain two new species of whitefly-transmitted, tomato-infecting plant picorna-like viruses: Tomato torrado virus and Tomato marchitez virus. So far, research on torradoviruses has focused mainly on the description of the viruses and the diseases they cause, the determination of viral properties and nucleic acid sequences, and the development of detection methods. Evidence has been found for the transmission of torradoviruses by three whitefly species in a semipersistent, stylet-borne manner.Key concepts included in this chapter:Discovery of TorradovirusesProperties of TorradovirusesTransmissionFuture Research

Uit dit onderzoek is gebleken dat planten die eerder in het seizoen worden geïnfecteerd, bol len geven met een hoger percentage TBV Plan ten die eenmalig een week voor het rooien wor den besmet, geven bijna geen zieke bollen. Bij infectie twee weken en langer voor het rooien loopt het percentage zieke bollen sterk op. Ook worden klisters later ziek dan de hoofdbol. Infec tie vindt blijkbaar plaats vanuit de plant via de hoofdbol naar de klisters. ln de praktijk vindt inl'e tiegedurende hei hele seizo n pla11 door pas r nde, vliegende blad luizen. In de praktijk i du ook ni t va 1 te tel len wanneer planten voor hel er t geïnfecteerd raken. Vrijwel zeker gebeurt dat ook al vroeg in het seizoen. In dat geval is er dus geen spra ke van een lager percentage virus in de kleine maten. De resultaten hebben betrekking op het onder zoek in een cultivar ('Strong Gold') en van een seizoen (2013-2014). Om beter gefundeerde conclusies te kunnen trekken is vervolgonder zoek gestartin het seizoen 2014-2015 met twee cultivars. Het actieplan 'Minder virus in tulp' is een gezamenlijk initiatief van Wageningen UR, PPO Bloembollen, Boomkwekerij & Fruit, Proeftuin Zwaagdijk, KAVB,LTO en BKD.

In October 2006, tomato plants with torrado disease were sampled in Spain. In a sample of cv. Mariana, originating from Gran Canaria, Tomato torrado virus (ToTV, genus Torradovirus) was detected (isolate GCN06; Alfaro-Fernández et al., 2010). In 2013, the sample was further analysed using next-generation sequencing (NGS). Total RNA, extracted from ca. 150 mg of leaf tissues, was used for an RNA library suitable for Illumina HiSeq paired end sequencing. A de novo assembly (using CLC Genomic Workbench v.6.5) resulted in 1380 sequence contigs. BLAST searches revealed the presence of ToTV and Tomato chlorosis virus (ToCV, genus Crinivirus). One contig (3427 nts, 8901 reads), showed 99.85% identity with Southern tomato virus (STV, genus Amalgavirus), isolate Mexico-1 (GenBank accession No. EF442780), a dsRNA seed-transmitted virus (Sabanadzovic et al., 2009). Reference assembly with the Mexico-1 sequence resulted in a partial sequence of 3420 nts (GenBank KJ174690). The presence of STV in sample GCN06 was verified in RT-PCR using the specific primers STV-fw and STV-rev (Candresse et al., 2013) and sequencing of the obtained amplicon. A new sampling in May 2014 in Gran Canaria revealed the presence of STV in six out of seven tomato samples of cv Mariana. All these samples were co-infected with Pepino mosaic virus (PepMV, genus Potexvirus), Tomato spotted wilt virus (TSWV, genus Tospovirus), and Tomato yellow leaf curl virus (TYLCV, genus Begomovirus). Because STV was generally found in samples co-infected with other viruses, its symptomatology in tomato remains unclear. To our knowledge, this is the first report of STV in the Canary Islands and Spain.

In Belgium and the Netherlands phytoplasma diseases mainly affect fruit trees, while they are almost absent in the United Kingdom. Specific insect vectors were identified and strict measures to eliminate both pathogens and pests are actively implemented in Belgium and the Netherlands

Taxonomy lies at the uneasy interface between biology and logic. The processing of information follows somewhat different rules in these two systems and the role of taxonomy is to reconcile them as tidily as possible. To this end, the Virology Division of the International Union of Microbiological Societies (IUMS) charged the International Committee on Taxonomy of Viruses (ICTV) with the task of developing, refining, and maintaining a universal virus taxonomy. The goal of this undertaking is to categorize the multitude of known viruses into a single classification scheme that reflects their evolutionary relationships, i.e. their individual phylogenies. The most recent report of the ICTV: "Virus taxonomy: classification and nomenclature of viruses: Ninth Report of the International Committee on Taxonomy of Viruses

Taxonomy lies at the uneasy interface between biology and logic. The processing of information follows somewhat different rules in these two systems and the role of taxonomy is to reconcile them as tidily as possible. To this end, the Virology Division of the International Union of Microbiological Societies (IUMS) charged the International Committee on Taxonomy of Viruses (ICTV) with the task of developing, refining, and maintaining a universal virus taxonomy. The goal of this undertaking is to categorize the multitude of known viruses into a single classification scheme that reflects their evolutionary relationships, i.e. their individual phylogenies. The most recent report of the ICTV: "Virus taxonomy: classification and nomenclature of viruses: Ninth Report of the International Committee on Taxonomy of Viruses

The invention relates to the field of virology. The invention provides an isolated plant virus (ToCh V) named Tomato chocolate virus (ToCh V), and components thereof. The invention further relates to methods of producing a ToCh V-resistant plant comprising the steps of identifying a ToCh V-resistant donor plant, crossing said ToCh V-resistant donor plant with a recipient plant, and selecting from an offspring plant a resistant plant.

Over the recent years Potato virus Y presents a growing problem in Dutch seed potato culture. In recent years a significant % of seed potato lots was de-classified due to PVY infections. This apparent increase in PVY infections was unexpected since no increase in field symptoms were observed and the numbers of aphids caught in the yellow water traps and high suction traps showed a clear decline over the last 10 years http://www.aab.org.uk/images/VIRO_CONF_PROG.pdf

The invention relates to the field of virology. The invention provides an isolated plant virus named Tomato Marchitez virus (ToMarV), and components thereof. The invention further relates to methods of producing a ToMarV- resistant plant comprising the steps of identifying a ToMarV-resistant donor plant, crossing said ToMarV-resistant donor plant with a recipient plant, and selecting from an offspring plant a resistant plant.

The invention relates to the field of virology. The invention provides an isolated plant virus (ToTV) named Tomato torrado virus (ToTV), and components thereof. The invention further relates to methods of producing a ToTV-resistant plant comprising the steps of identifying a ToTV-resistant donor plant, crossing said ToTV-resistant donor plant with a recipient plant, and selecting from an offspring plant a resistant plant.

Potato leafroll virus (PLRV), gênero Polerovirus, família Luteoviridae, é transmitido por afídeos de um modo persistente e circulativo. Membros da família Luteoviridae associam-se a um homólogo de GroEL produzido pelo endosimbionte primário (Buchnera sp.) de afídeos para evitar a degradação na hemolinfa. Partículas purificadas de luteovirus contêm dois tipos de proteínas: a capa protéica (CP) de ~22 kDa e um componente "capsidial" de 54 kDa, o qual é uma forma truncada de uma proteína de "transleitura" a partir do códon de terminação do gene da CP. O domínio de transleitura (RTD) contém determinantes responsáveis pela transmissão do vírus. Um clone de cDNA infeccioso do PLRV e um mutante deletério da RTD foram usados para analisar as interações entre esse luteovirus e seu afídeo vetor Myzus persicae. As partículas mutantes do PLRV, deficientes da proteína RTD inteira, não foram transmissíveis por M. persicae e não se ligaram a Buchnera GroEL. Adicionalmente, esse mutante foi menos persistente na hemolinfa do afídeo do que o vírus selvagem. Potato leafroll virus (PLRV), genus Polerovirus, family Luteoviridae, is transmitted by aphids in a persistent and circulative manner. Members of the family Luteoviridae associate with a GroEL homologue produced by the primary endosymbiont (Buchnera sp.) of aphids to avoid degradation in the hemolymph. Purified luteovirus particles contain two types of proteins: a major capsid protein (CP) of ~22 kDa and a minor capsid component of 54 kDa, which is a truncated form of a translation read-through protein of the CP gene termination codon. The read-through domain (RTD) contains determinants responsible for virus transmission. An infectious full-length cDNA clone of PLRV and a mutant devoid of the RTD were used to analyze the molecular interactions between this luteovirus and its aphid vector Myzus persicae. The PLRV mutant virions, lacking the entire RTD protein, were not transmissible by M. persicae and did not bind to Buchnera sp. GroEL. Furthermore, this mutant was less persistent in the aphid's hemolymph than in the wild type virus.

Luteoviruses avoid degradation in the hemolymph of their aphid vector by interacting with a GroEL homolog from the aphid's primary endosymbiotic bacterium (Buchnera sp.). Mutational analysis of GroEL from the primary endosymbiont of Myzus persicae (MpB GroEL) revealed that the amino acids mediating binding of Potato leafroll virus (PLRV; Luteoviridae) are located within residues 9 to 19 and 427 to 457 of the N-terminal and C-terminal regions, respectively, of the discontinuous equatorial domain. Virus overlay assays with a series of overlapping synthetic decameric peptides and their derivatives demonstrated that R13, K15, L17, and R18 of the N-terminal region and R441 and R445 of the C-terminal region of the equatorial domain of GroEL are critical for PLRV binding. Replacement of R441 and R445 by alanine in full-length MpB GroEL and in MpB GroEL deletion mutants reduced but did not abolish PLRV binding. Alanine substitution of either R13 or K15 eliminated the PLRV-binding capacity of the other and those of L17 and R18. In the predicted tertiary structure of GroEL, the determinants mediating virus binding are juxtaposed in the equatorial plain.