The melon resistance gene pair: Correlated spatial expression and interaction with a viral protein.

The head-to-head oriented pair of melon resistance genes, and , control resistance to races 0 and 2 and papaya ringspot virus (PRSV), respectively. They encode, via several RNA splice variants, TIR-NBS-LRR proteins, and Prv has a C-terminal extra domain with a second NBS homologous sequence. In other systems, paired R-proteins were shown to operate by "labor division," with one protein having an extra integrated domain that directly binds the pathogen's Avr factor, and the second protein executing the defense response.

A single substitution in Vacuolar protein sorting 4 is responsible for resistance to Watermelon mosaic virus in melon.

In plants, introgression of genetic resistance is a proven strategy for developing new resistant lines. While host proteins involved in genome replication and cell to cell movement are widely studied, other cell mechanisms responsible for virus infection remain under investigated. Endosomal sorting complexes required for transport (ESCRT) play a key role in membrane trafficking in plants and are involved in the replication of several plant RNA viruses.

Specificity of Resistance and Tolerance to Cucumber Vein Yellowing Virus in Melon Accessions and Resistance Breaking with a Single Mutation in VPg.

Cucumber vein yellowing virus (CVYV) is an emerging virus on cucurbits in the Mediterranean Basin, against which few resistance sources are available, particularly in melon. The melon accession PI 164323 displays complete resistance to isolate CVYV-Esp, and accession HSD 2458 presents a tolerance, i.e.

The Bunyavirales: The Plant-Infecting Counterparts.

Negative-strand (-) RNA viruses (NSVs) comprise a large and diverse group of viruses that are generally divided in those with non-segmented and those with segmented genomes. Whereas most NSVs infect animals and humans, the smaller group of the plant-infecting counterparts is expanding, with many causing devastating diseases worldwide, affecting a large number of major bulk and high-value food crops. In 2018, the taxonomy of segmented NSVs faced a major reorganization with the establishment of the order .

Complete sequence of an isolate of snake melon asteroid mosaic virus confirms that it is a member of a distinct sobemovirus species.

A virus tentatively named "snake melon asteroid mosaic virus" (SMAMV) was found in Sudan in cucurbit crops (10% of 600 samples) between 1992 and 2003. Biological and cytological properties as well as sequence data on a 345-nt fragment suggested that SMAMV was a member of the genus Sobemovirus. However, no complete sequence had been obtained, and the relationship between SMAMV and the acknowledged sobemoviruses had not been ascertained.

Emerging strains of watermelon mosaic virus in Southeastern France: model-based estimation of the dates and places of introduction.

Where and when alien organisms are successfully introduced are central questions to elucidate biotic and abiotic conditions favorable to the introduction, establishment and spread of invasive species. We propose a modelling framework to analyze multiple introductions by several invasive genotypes or genetic variants, in competition with a resident population, when observations provide knowledge on the relative proportions of each variant at some dates and places. This framework is based on a mechanistic-statistical model coupling a reaction-diffusion model with a probabilistic observation model.

Detection and complete genome sequence of a divergent isolate of cucumber fruit mottle mosaic virus on Coccinia grandis in Sudan.

Cucurbit-infecting tobamoviruses known so far belong to six acknowledged or tentative species. Except for cucumber green mottle mosaic virus (CGMMV), which is present worldwide, they are geographically restricted, mostly to Asia, and have not been observed in Africa so far. A tobamovirus isolate infecting a wild Coccinia grandis plant was collected in central Sudan in 2012.

Distribution and evolution of the major viruses infecting cucurbitaceous and solanaceous crops in the French Mediterranean area.

Plant viral diseases represent a significant burden to plant health, and their highest impact in Mediterranean agriculture is on vegetables grown under intensive horticultural practices. In order to understand better virus evolution and emergence, the most prevalent viruses were mapped in the main cucurbitaceous (melon, squashes) and solanaceous (tomato, pepper) crops and in some wild hosts in the French Mediterranean area, and virus diversity, evolution and population structure were studied through molecular epidemiology approaches. Surveys were performed in summer 2016 and 2017, representing a total of 1530 crop samples and 280 weed samples.

Host Range Evolution of Potyviruses: A Global Phylogenetic Analysis.

Virus host range, i.e., the number and diversity of host species of viruses, is an important determinant of disease emergence and of the efficiency of disease control strategies.

Sixty Years After the First Description: Genome Sequence and Biological Characterization of European Wheat Striate Mosaic Virus Infecting Cereal Crops.

High-throughput sequencing technologies were used to identify plant viruses in cereal samples surveyed from 2012 to 2017. Fifteen genome sequences of a tenuivirus infecting wheat, oats, and spelt in Estonia, Norway, and Sweden were identified and characterized by their distances to other tenuivirus sequences. Like most tenuiviruses, the genome of this tenuivirus contains four genomic segments.

Resistance Against Melon Chlorotic Mosaic Virus and Tomato Leaf Curl New Delhi Virus in Melon.

Thirty-one melon accessions were screened for resistance to the begomoviruses (MeCMV) and (ToLCNDV). Five accessions presented nearly complete resistance to both viruses. Accession IC-274014, showing the highest level of resistance to both viruses, was crossed with the susceptible cultivar Védrantais.

Inferring epidemiological links from deep sequencing data: a statistical learning approach for human, animal and plant diseases.

Pathogen sequence data have been exploited to infer who infected whom, by using empirical and model-based approaches. Most of these approaches exploit one pathogen sequence per infected host (e.g.

Characterization of the first tenuivirus naturally infecting dicotyledonous plants.

A mechanically transmissible virus tentatively named "melon chlorotic spot virus" (MeCSV) was isolated in southeastern France from a melon plant showing chlorotic spots and yellowing of the older leaves. Its complete sequence was obtained by Illumina and Sanger sequencing. The genome comprises eight RNAs for a total size of 20,079 nt and is distantly related to Ramu stunt virus and maize yellow stunt virus, two tentative tenuiviruses.

New species in the papaya ringspot virus cluster: Insights into the evolution of the PRSV lineage.

The "Papaya ringspot virus (PRSV) cluster" of cucurbit-infecting potyviruses contains five acknowledged species that have similar biological, serological and molecular properties. Additional data suggest there are other uncharacterized species from various locations in the world that likely belong to the PRSV cluster including a new PRSV-like virus reported from Sudan in 2003. Molecular and biological data indicated that the virus from Sudan belongs to a new species, tentatively named wild melon vein banding virus (WMVBV).

Molecular and biological characterization of a new Tomato mild yellow leaf curl Aragua virus strain producing severe symptoms in tomato.

Tomato mild yellow leaf curl Aragua virus (ToMYLCV) is a begomovirus first reported infecting tomato (Solanum lycopersicum) and milkweed (Euphorbia heterophylla) in Venezuela. In this study, a ToMYLCV isolate (Zulia-219) was completely sequenced and its host range was evaluated. The DNA-A and DNA-B components of isolate Zulia-219 showed 93 and 85% nucleotide sequence identity with the respective counterparts of the ToMYLCV type strain.

Impact of Vat resistance in melon on viral epidemics and genetic structure of virus populations.

Cultivar choice is at the heart of cropping systems and resistant cultivars should be at the heart of disease management strategies whenever available. They are the easiest, most efficient and environmentally friendly way of combating viral diseases at the farm level. Among the melon genetic resources, Vat is a unique gene conferring resistance to both the melon aphid Aphis gossypii and the viruses it carries.

Evidence for positive selection and recombination hotspots in Deformed wing virus (DWV).

Deformed wing virus (DWV) is considered one of the most damaging pests in honey bees since the spread of its vector, Varroa destructor. In this study, we sequenced the whole genomes of two virus isolates and studied the evolutionary forces that act on DWV genomes. The isolate from a Varroa-tolerant bee colony was characterized by three recombination breakpoints between DWV and the closely related Varroa destructor virus-1 (VDV-1), whereas the variant from the colony using conventional Varroa management was similar to the originally described DWV.

Characterization of a new cucurbit-infecting ipomovirus from Sudan.

Two members of the genus Ipomovirus (family Potyviridae) are known to infect cucurbits: cucumber vein yellowing virus (CVYV), which is emerging throughout the Mediterranean Basin, and squash vein yellowing virus (SqVYV), which has been described in America and the Caribbean Basin, and more recently in Israel. In this work, an ipomovirus different from CVYV and SqVYV, tentatively named coccinia mottle virus (CocMoV), was detected in a sample of the cucurbit Coccinia grandis collected in central Sudan in 2012. Sequence identity in nt was 68 % with CVYV, 59-60 % with SqVYV, cassava brown streak virus and Ugandan cassava brown streak virus, and less than 50 % with other members of the family Potyviridae.

Characterization and occurrence of squash chlorotic leaf spot virus, a tentative new torradovirus infecting cucurbits in Sudan.

During a survey conducted in Sudan in 2012, a virus with spherical particles was isolated from a squash plant showing chlorotic leaf spots. The virus was transmitted mechanically and by two whitefly species, but not by aphids. RT-PCR with generic torradovirus primers yielded a band of expected size from total RNA of a symptomatic plant.

Cloning of the Arabidopsis rwm1 gene for resistance to Watermelon mosaic virus points to a new function for natural virus resistance genes.

Arabidopsis thaliana represents a valuable and efficient model to understand mechanisms underlying plant susceptibility to viral diseases. Here, we describe the identification and molecular cloning of a new gene responsible for recessive resistance to several isolates of Watermelon mosaic virus (WMV, genus Potyvirus) in the Arabidopsis Cvi-0 accession. rwm1 acts at an early stage of infection by impairing viral accumulation in initially infected leaf tissues.

Comparative molecular epidemiology provides new insights into Zucchini yellow mosaic virus occurrence in France.

Zucchini yellow mosaic virus (ZYMV, genus Potyvirus) causes important crop losses in cucurbits worldwide. In France, ZYMV epidemics are sporadic but occasionally very severe. This contrasts with Watermelon mosaic virus (WMV, genus Potyvirus) which causes regular and early epidemics.

First Report of Watermelon mosaic virus Naturally Infecting Cucumis anguria.

Watermelon mosaic virus (WMV, Potyvirus) is an important virus of cucurbit crops worldwide, although it is rarely found in tropical regions. Cucumis anguria L. is a native species from tropical regions of Africa and can be found as a volunteer or cultivated plant in the Neotropic (1).

A short motif in the N-terminal part of the coat protein is a host-specific determinant of systemic infectivity for two potyviruses.

Although the biological variability of Watermelon mosaic virus is limited, isolates from the three main molecular groups differ in their ability to infect systemically Chenopodium quinoa. Mutations were introduced in a motif of three or five amino acids located in the N-terminal part of the coat protein, and differing in isolates from group 1 (motif: lysine-glutamic acid-alanine (Lys-Glu-Ala) or KEA, systemic on C. quinoa), group 2 (Lys-Glu-Thr or KET, not systemic on C.