Résumé
The Mastrevirus genus (family Geminiviridae) contains circular single-stranded DNA viruses transmitted by leafhopper vectors to a wide range of plants, including monocots and dicots. The most studied mastreviruses are those circulating in Africa and infecting monocots. This group of mastrevirus, referred to as the African streak viruses (AfSV), comprises 13 species infecting cultivated and wild Poaceae species. Three decades of mastreviruses research in La Réunion demonstrates the presence of six of these species on the island. Interestingly, these species were probably introduced at different time and present with putative distinct host range. Understanding how this virus community operates remains an essential question in the understanding of virus ecology, evolution and emergence. Therefore, to elucidate the diversity, host ranges and structure of mastrevirus communities in La Réunion, we undertook an extensive survey in a single sampling site of one acre including crop fields, orchards and uncultivated areas. After four sampling campaigns, 2889 samples of 28 cultivated and uncultivated Poaceae species were collected, with most samples apparently symptomless. Total plant DNA was isolated and circular viral genomes were amplified by a sequence-independent amplification procedure combining rolling circle amplification, a random amplification tagging (RCA-RA) and high-throughput sequencing (Illumina HiSeq). For every sample, mastrevirus reads were classified using phylogenetic placement within species and strains. Mastrevirus species were confirmed by cloning and Sanger sequencing.Besides uncovering previously undescribed mastrevirus species, our results provide an exhaustive view of the mastrevirus-host association network within an agrosystem. The topology of this network suggests (1) the co-existence of viruses ranging from generalist to specialist and (2) that certain hosts may act as hub of viruses. The impact of such a structure over the functioning of communities (co-infections frequencies, degree of recombination and rates of adaptation) will be discussed.