Interet des etudes sur la variabilite naturelle du virus de la mosaique du concombre et des Cucumovirus

National audienc

Thirty years of France'experience in the production of disease-free garlic and shallot mother bulbs

International Symposium Allium for the tropics; Bangkok (Thaïlande) - (1993-02-15 - 1993-02-19)International audienceThirty years ago in France, sanitary and clonal selection in garlic began for a cultivar which remained free of onion yellow dwarf virus (OYDV). Through meristem culture 10 years later, symptomless plants were obtained from cultivars in which virus infestation was 100%. Symptomless clones are multiplied by farmers following regulations on rotation, isolation from other allium crops, rouging diseased plants, and inspection of the plots, in order to attain mother bulbs free of virus symptoms, nematodes, and white rot. A similar system is used for multiplication of OYDV-free shallot clones. The complexity of the virological situation in these vegetatively propagated alliums was exposed through the use of the electron microscope. Only in 1981 was this situation fully understood for garlic, by the use of the immuno-electromicroscopy method. In some years, problems are caused by very early and numerous aphid flights. As a consequence, the first generations of multiplication are increasingly grown under insect-proof screenhouses. Annual French-certified mother-bulb production is about 2 500 tons for garlic and 400 tons for shallot. The partners of the research institute for this production scheme are cooperatives or farmers' associations

L'ARN satellite du virus de la mosaïque du concombre III. - La propriété de survie in vivo

International audienc

Utilisation des résistances au BWYV et au LMV découvertes chez L. virosa

annexes techniques 41

Nucleotide sequence and genomic organization of cacao swollen shoot virus

International audienceCacao swollen shoot virus is classified as a badnavirus based on its nonenveloped, bacilliform particle morphology and double-stranded DNA genome. A complete copy of the genome was cloned into a plasmid vector and the sequence was determined from 75 overlapping subclones covering both strands. The genome contains 7161 base pairs and possesses an intergenic region and five putative open reading frames (ORF) capable of coding for proteins > 10 kDa. All of the ORFs are present on the plus-strand. ORF 1 (17 kDa) and ORF 2 (14 kDa) encode proteins of unknown function. The large ORF 3 (211 kDa) encodes a polyprotein that can be divided into three regions. Based on distant homologies with viral movement proteins, region 1 may encode a protein involved in cell-to-cell spread, while region 2 encodes the viral capsid protein. Region 3 contains consensus sequences for viral aspartyl proteinase, reverse transcriptase, and ribonuclease H characteristic of pararetroviruses. The last two ORPs (13 and 14 kDa) overlap ORF 3 and are not present in the other badnaviruses described

Analyse de LMV recombinants portant des propriétés biologiques surprenantes

International audienc

Mapping of the virulence determinants in lettuce mosaic virus spontaneous variants

International audienc

Nucleotide sequence of the 3' terminal region of lettuce mosaic potyvirus RNA shows a Gln/Val dipeptide at the cleavage site between the polymerase and the coat protein

International audienceDNA complementary to the 3′ terminal 1651 nucleotides of the genome of the common strain of lettuce mosaic virus (LMV-O) has been cloned and sequenced. Microsequencing of the N-terminus enabled localization of the coat protein gene in this sequence. It showed also that the LMV coat protein coding region is at the 3′ end of the genome, and that the coat protein is processed from a larger protein by cleavage at an unusual Q/V dipeptide between the polymerase and the coat protein. This is the first report of such a site for cleavage of a potyvirus polyprotein, where only Q/A, Q/S, and Q/G cleavage sites have been reported. The LMV coat protein gene encodes a 278 amino acid polypeptide with a calculated Mr of 31,171 and is flanked by a region which has a high degree of homology with the putative polymerase and a 3′ untranslated region of 211 nucleotides in length. Percentage of homology with the coat protein of other potyviruses confirms that LMV is a distinct member of this group. Moreover, amino acid homologies noticed with the coat protein of potexvirus, bymovirus, and carlavirus elongated plant viruses suggest a functional significance for the conserved domains

Comparaison des propriétés biologiques et de la variabilité moléculaire du virus de la mosaïque de la laitue (LMV)

National audienc