Secoviridae: a proposed family of plant viruses within the order Picornavirales that combines the families Sequiviridae and Comoviridae, the unassigned genera Cheravirus and Sadwavirus, and the proposed genus Torradovirus

The order Picornavirales includes several plant viruses that are currently classified into the families Comoviridae (genera Comovirus, Fabavirus and Nepovirus) and Sequiviridae (genera Sequivirus and Waikavirus) and into the unassigned genera Cheravirus and Sadwavirus. These viruses share properties in common with other picornavirales (particle structure, positive-strand RNA genome with a polyprotein expression strategy, a common replication block including type III helicase, a 3C-like cysteine proteinase and type I RNA-dependent RNA polymerase). However, they also share unique properties that distinguish them from other picornavirales. They infect plants and use specialized proteins or protein domains to move through their host. In phylogenetic analysis based on their replication proteins, these viruses form a separate distinct lineage within the picornavirales branch. To recognize these common properties at the taxonomic level, we propose to create a new family termed “Secoviridae” to include the genera Comovirus, Fabavirus, Nepovirus, Cheravirus, Sadwavirus, Sequivirus and Waikavirus. Two newly discovered plant viruses share common properties with members of the proposed family Secoviridae but have distinct specific genomic organizations. In phylogenetic reconstructions, they form a separate sub-branch within the Secoviridae lineage. We propose to create a new genus termed Torradovirus (type species, Tomato torrado virus) and to assign this genus to the proposed family Secoviridae

Specificity, exclusivity and complementarity in the transmission of plant viruses by plant parasitic nematodes : an annotated terminology

Dix-huit espèces de nématodes phytoparasites appartenant aux genres #Longidorus, #Paralongidorus et #Xiphinema sont vectrices de douze nepovirus, tandis que treize espèces des genres #Paratrichodorus et #Trichodorus$ sont vectrices de trois tobravirus. Une caractéristique de ces nématodes vecteurs et de leurs associations avec les virus avait été rapidement reconnue lorsque des nepovirus sérologiquement distincts et des souches différentes de virus avaient été reconnus transmis par des espèces de Longidorides différentes, mais proches. Les virus avaient donc été considérés comme ayant des espèces vectrices "spécifiques", ce qui avait conduit à adopter une terminologie suivant laquelle les chercheurs faisaient référence à la "spécificité" de la transmission des virus par les nématodes vecteurs. En outre, la spécificité de la transmission avait été confirmée par des recherches ultérieures et démontrée s'étendre au niveau des populations des espèces vectrices et à celui de variants sérologiques mineurs des nepovirus. Il a été également démontré que ce phénomène s'applique aux tobravirus et à leurs vecteurs. Sont décrits dans cet article les mécanismes qui pourraient déterminer l'association entre les nématodes vecteurs et leurs virus. Sont également données et expliquées les définitions d'un certain nombre de termes et concepts utilisés lors des recherches sur les vections par les nématodes. (Résumé d'auteur

Fanleaf degeneration/decline disease of grapevines

NYS IPM Type: Fruits IPM Fact SheetFanleaf degeneration/decline disease is one of the most severe viral disease complexes of grapevine worldwide. It is also one of the oldest known viral diseases of Vitis vinifera with descriptions of symptoms being reported in Europe as early as 1841. This disease is now known to affect grapevines in all temperate regions where Vitis vinifera and hybrid rootstocks are grown. Within the United States, fanleaf degeneration/decline is widespread in California, but has also been observed in Washington State, Maryland, Pennsylvania, New York and Missouri

Multiple interspecies recombination events within RNA2 of Grapevine fanleaf virus and Arabis mosaic virus

Sequence alignments and SISCAN analyses inferred multiple interspecies recombination events within RNA2 of strains GHu of Grapevine fanleaf virus (GFLV) and Ta of Arabis mosaic virus (ArMV), two closely related subgroup A nepoviruses in the family Comoviridae. Interspecies recombination events were identified in the 5′ untranslated region, the putative homing protein and movement protein genes but not in the coat protein gene and 3′ untranslated region. These findings suggest a dynamic relationship between GFLV and ArMV, and a differential selection pressure on RNA2-encoded proteins with constraints in terms of function and co-adaptation that limit interspecies recombination to certain gene segment

Pest categorisation of Xiphinema californicum

The Panel on Plant Health performed a pest categorisation of Xiphinema californicum (Nematoda: Longidoridae) for the EU. The nematode is a well-defined taxon belonging to a group of morphologically similar species called Xiphinema americanum sensu lato. The nematode was described from the USA and is present in some North and South American countries. The nematode is not present in the EU and is regulated by Council Directive 2000/29/EC, listed in Annex I A I as X. californicum Lamberti and Bleve-Zacheo. It is a polyphagous pest found in soil associated with a number of plant species. As a migratory ectoparasitic species, it punctures the cells of plant roots. X. californicum is in principle able to cause direct damage to plants, but its main damage is caused by vectoring the American nepoviruses: Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV) and Cherry rasp leaf virus (CRLV). Soil is a potential pathway for this nematode for entry into the EU. Moist soil, such as soil attached to plants for planting, increases survival of the nematode. The viruses may persist over prolonged periods inside the nematode and viruliferous nematodes may introduce American nepoviruses. Climatic conditions in the EU are similar to those found in the areas where the pest is currently present. Hosts of the nematode (and of associated viruses) are, e.g. grapes, apples and plums, which are also widely cultivated in the EU. The nematode only moves short distances (around 1 m) but may be spread with soil moving activities. Measures are available to inhibit entry via soil as such. Entry of the nematode with soil attached to plants for planting that are not regulated is possible. X. californicum does satisfy all the criteria that are within the remit of EFSA to assess to be regarded as a Union quarantine pest

Evidence of non-seed transmission of viruses in grapevine breeding material

The vertical transmission of viruses is an important phenomenon affecting a wide range of viruses and host plants. Nevertheless, the presence of virus in a seed does not always lead to seedling infection. In grapevine, seed transmission has been reported for many nepoviruses, but little is known about Leafroll, Rugose wood complex and Fleck diseases. Thus, the aim of this study is to monitor the virological condition of seedlings obtained by crosses between infected parents, analyzing the sanitary status of seedlings after the transfer in experimental fields. It was observed that, although the viral state of parents was quite compromised, viruses were not detected in any of the 150 progeny plants, demonstrating that the main grapevine viruses are at low risk for seed transmission

Occurrence of small fruit viruses in Belarus

Epidemiological control of plant virus diseases is necessary for creation of small fruit nurseries and production of berries with stable high yields. Phytosanitary state of Rubus idaeus L. and Ribes sp. L. was studied in Belarus. The aim of the research was to determine the most widespread small fruit viruses and to select plants that free from all tested viruses for further propagation in vitro as a basis for Nuclear stock. The following viruses were identified: CMV, ApMV, SLRV, RRV, RBDV, ArMV, TBRV and ToRSV. High level of virus infection for small fruit plantations was shown. The most common viruses for all three crops (raspberry, red and black currant) were RRV, SLRV and ArMV. It was noted that infection level of viruses considerably varied from plant cultivars and crops.Keywords: Viruses, raspberry, black currant, red currant, Belaru