Description préliminaire d’un potyvirus isolé de courgette (Cucurbita pepo L.) en Guadeloupe

En Guadeloupe, le virus 1 de la mosaïque de la pastèque, Papaya Ringspot Virus-Watermelon (PRSV-W)= Watermelon Mosaic Virus 1 (WMV-1), est très répandu dans les cultures de courgette où il provoque des symptômes de mosaïque avec cloques et des déformations filiformes très marquées sur le feuillage et également des déformations de fruits. Depuis 1982, on a constaté qu’un autre faciès maladif était aussi épidémique dans les champs de courgette. Il se distingue de celui de PRSV-W par une mosaïque donnant un aspect tigré au feuillage et l’absence de déformation filiforme. L’isolat (Q10) provenant de l’une des plantes infectées par la souche « Tigré » a été étudié. Le virus est transmissible par inoculation mécanique. Il est transmis par puceron sur le mode non persistant mais à un taux différent de celui observé pour le PRSV-W. Sa gamme d’hôtes est analogue à celle du PRSV-W. Elle est limitée à la famille des Cucurbitacées et en particulier, les génotypes de Cucumis melo, C. metuliferus, Cucurbita ecuaderensis et C. foetidissima résistants au PRSV-W sont aussi résistants à l’isolat Q10. Les particules virales sont flexueuses. L’infection induit dans le cytoplasme la formation d’inclusions amorphes et d’inclusions cylindriques se classant dans la subdivision I. Des tests sérologiques d’immunodiffusion en présence de dodécyl-sulfate de sodium et des tests en ISEM (Immunosorbent Electron Microscopy) ont montré que l’isolat Q10 ne réagissait avec aucun des sérums dont nous disposions préparés contre les virus suivants : PRSV-W, Watermelon Mosaic Virus 2 (WMV-2), Watermelon Mosaic Virus « Morocco » (WMV-M), Zucchini Yellow Mosaic Virus (ZYMV), Zucchini Yellow Fleck Virus (ZYFV). Inversement, PRSV-W, WMV2 et ZYMV n’ont pas réagi avec le sérum préparé spécifiquement contre l’isolat Q10. L’isolat Q10 a des propriétés biologiques proches de celles du PRSV-W ; il s’en distingue par son taux de transmission par puceron, sa symptomatologie sur certains hôtes et par ses propriétés sérologiques. Une étude complémentaire permettra d’établir si cet isolat doit être considéré comme un sérotype du PRSV-W ou comme un virus à part entière.In Guadeloupe, a Caribbean island, the watermelon strain of papaya ringspot virus (PRSV-W = watermelon mosaic virus 1, WMV-1) is commonly encountered in squash fields. It induces a severe mosaic with blistering and filiformism on squash leaves, and a deformation of fruits. Since 1982, a new disease has been found epidemically in squash fields, the symptoms being leaf discoloration according to a striped ("Tigre") pattern and limited filiformism. An isolate (Q10), collected from a squash showing the "Tigre" symptom, was studied. The virus was transmitted mechanically and also transmitted by aphids in the non-persistent manner and less efficiently than PRSV-W. Its host range was similar to that of PRSV-W. It was restricted to the Cucurbit family, and genotypes of Cucumis melo, C. metuliferus, Cucurbita ecuadorensis and C. foetidissima resistant to PRSV-W were also resistant to isolate Q10. Virus particles were filamentous. Infection induced in the cytoplasm the formation of amorphous and cylindrical type I inclusions. Sodium dodecyl sulfateimmunodiffusion and ISEM (Immunosorbent Electron Microscopy) tests showed that isolate Q10 did not react with sera prepared against the following viruses : PRSV, watermelon mosaic virus 2 (WMV-2) watermelon mosaic virus "Morocco" (WMV-M), zucchini yellow mosaic virus (ZYMV), zucchini yellow fleck virus (ZYFV). Conversely, PRSV-W, WMV-2 ans ZYMV did not react with the serum specifically prepared against isolate Q10. Some biological properties of isolate Q10 and PRSV-W were similar but the viruses could be distinguished by their aphid transmission rate, symptoms on some hosts and serological properties. Further studies will show whether this isolate should be considered as a new serotype of PRSV or as a new virus

La mesure du taux de transmission d'un virus non-persistant par puceron. Definition d'un test pratique et application a l'etude du comportement de 2 souches du virus des taches en anneau du papayer (PRSV)

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Pathogenicity determinants in the complex virus population of a plum pox virus isolate

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Plum pox virus diversification observed in a small cluster of orchards

International audienceSixty-six isolates were collected during several years (1992 to 1999), along an east-west transect in a Plum pox potyvirus (PPV) focus located in southern France. Amplification by PCR of both ends of viral coat protein genes, followed by restriction analysis, showed the existence of a PPV natural diversity with a filiation of the variants collected along the transect. These results were confirmed by the micro-sequencing of a selected number of isolates. These data show that an aphid transmissible virus infecting perennial woody plants can induce a sustainable local variability, particularly at the margin of an expanding focus

Identification of plum pox virus determinants implicated in specific interactions with different Prunus spp.

UMR BGPI - Equipe 6 Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThe characterization of pathogenic properties of two infectious clones of Plum pox virus (PPV) isolates, pGPPV (D group) and pGPPVPS (M group), was investigated in their woody hosts (seedlings of Prunus spp.). The two clones differed in their ability to infect plum and peach cultivars, from no infection to local and systemic infection. The phenotype determinants were located with a set of chimeric viruses from the two clones. In plum, determinants of systemic infection were located in a genomic fragment encoding the P3 and 6K1 proteins, which might influence genome amplification or virus movement. The capacity of pGPPVPS to induce stable local and systemic infections in peach was not located accurately and might be influenced by multiple determinants carried by different regions of the genome, excluding those encoding the protein 1, the majority of helper component, nuclear inclusions a and b, and coat protein. We conclude that PPV infections of plum and peach are governed by different determinants

In vitro inoculation of Prunus species with plum pox potyvirus

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Identification of a pathogenicity determinant of Plum pox virus in the sequence encoding the C-terminal region of protein P3 + 6K1

UMR BGPI Equipe 6 Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceA full-length genomic cDNA clone of a plum pox potyvirus (PPV) isolate belonging to the M strain (PPV-PS) has been cloned downstream from a bacteriophage T7 polymerase promoter and sequenced. Transcripts from the resulting plasmid, pGPPVPS, were infectious and, in herbaceous hosts, produced symptoms that differed from those of virus progeny of pGPPV, a full-length genomic cDNA clone of the D strain PPV-R. Viable PPV-R/-PS chimeric viruses were constructed by recombination of the cDNA clones in vitro. Analysis of plants infected with the different chimeras indicated that sequences encoding the most variable regions of the potyvirus genome, the P1 and capsid protein coding sequences, were not responsible for symptom differences between the two PPV isolates in herbaceous hosts. On the contrary, complex symptomatology determinants seem to be located in the central region of the PPV genome. The results indicate that a genomic fragment that encodes 173 aa from the C-terminal part of the P3+6K1 coding region is enough to confer, on a PPV-R background, a PS phenotype in Nicotiana clevelandii. This pathogenicity determinant also participates in symptom induction in Pisum sativum, although the region defining the PS phenotype in this host is probably restricted to 74 a

Host-specific effect of P1 exchange between two potyviruses

International audienceThe potyviruses Plum pox virus (PPV) and Tobacco vein mottling virus (TVMV) have distinct host ranges and induce different symptoms in their common herbaceous hosts. To test the relevance of the P1 protein in host compatibility and pathogenicity, hybrid viruses were constructed in which the P1 coding sequence of PPV was completely or partially replaced by the corresponding sequences from TVMV. Infections induced by these chimeric viruses revealed that the TVMV P1 and a PPV/TVMV hybrid P1 proteins are functionally equivalent in herbaceous plants to the P1 protein of a PPV isolate adapted to these hosts, in spite of having high sequence divergence. Moreover, the presence of TVMV P1 sequences enhanced the competence of a low-infectivity PPV-D-derived chimera in Nicotiana clevelandii. Conversely, all PPV/TVMV hybrids were unable to infect Prunus persicae, a specific host for PPV, suggesting that TVMV P1 is not functionally competent in this plant. Together, these data highlight the importance of the P1 protein in defining the virus host range

Ecologie et épidémiologie du virus de la mosaïque du concombre dans le sud-est de la France. VI- Conservation de deux types de populations virales dans les plantes sauvages

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