Contributors: Unité de recherche TERRA Gembloux; Gembloux Agro-Bio Tech Faculté universitaire des sciences agronomiques de Gembloux ( FUSAGx ); Université de Liège = University of Liège = Universiteit van Luik = Universität Lüttich (ULiège)-Université de Liège = University of Liège = Universiteit van Luik = Universität Lüttich (ULiège); Université catholique de Bukavu; Earth and Life Institute - Environmental Sciences (ELIE); Université Catholique de Louvain = Catholic University of Louvain (UCL); Biologie du fruit et pathologie (BFP); Université de Bordeaux (UB)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE); Plant Health Institute of Montpellier (UMR PHIM); Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Université de Montpellier (UM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro; Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro); Département Systèmes Biologiques (Cirad-BIOS); Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad); Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT); Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE); Centre National de Recherche Appliquée au Développement Rural (FOFIFA); Catholic University of Leuven = Katholieke Universiteit Leuven (KU Leuven); This study was co-fundedin part by the European Union (ERDF, INTERREGV), the Conseil Régional de la Réunion and CIRAD,and conducted in part on the Plant Protection Platform (3P, IBISA)
نبذة مختصرة : International audience ; Cassava is one of the most important staple crops in Africa and its production is seriously damaged by viral diseases. In this study, we identify for the first time and characterize the genome organization of novel ampeloviruses infecting cassava plants in diverse geographical locations using three high-throughput sequencing protocols [Virion-Associated Nucleotide Acid (VANA), dsRNA and total RNA], and we provide a first analysis of the diversity of these agents and of the evolutionary forces acting on them. Thirteen new Closteroviridae isolates were characterized in field-grown cassava plants from the Democratic Republic of Congo (DR Congo), Madagascar, Mayotte, and Reunion islands. The analysis of the sequences of the corresponding contigs (ranging between 10,417 and 13,752 nucleotides in length) revealed seven open reading frames. The replication-associated polyproteins have three expected functional domains: methyltransferase , helicase, and RNA-dependent RNA polymerase (RdRp). Additional open reading frames code for a small transmembrane protein, a heat-shock protein 70 homolog (HSP70h), a heat shock protein 90 homolog (HSP90h), and a major and a minor coat protein (CP and CPd respectively). Defective genomic variants were also identified in some cassava accessions originating from Madagascar and Reunion. The isolates were found to belong to two species tentatively named Manihot esculenta-associated virus 1 and 2 (MEaV-1 and MEaV-2). Phylogenetic analyses showed that MEaV-1 and MEaV-2 belong to the genus Ampelovirus, in particular to its subgroup II. MEaV-1 was found in all of the countries of study, while MEaV-2 was only detected in Madagascar and Mayotte. Recombination analysis provided evidence of intraspecies recombination occurring between the isolates from Madagascar and Mayotte. No clear association with visual symptoms in the cassava host could be identified.
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