Résumé
Rice yellow mottle disease in western Burkina Faso: incidence, diversity and dynamics at local scaleD. Sérémé1, N. Poulicard2, E. Billard2, M. Barro1, M. Bangratz2, I. Wonni1, M. Koala1, A. I. Kassankogno1, E. Hébrard2, G. Thébaud2, C. Brugidou2, C. Tollenaere11 INERA, Institut de l'Environnement et de Recherches Agricoles du Burkina Faso, Département Productions Végétales, Burkina Faso 2 PHIM Plant Health Institute, Univ Montpellier, IRD, CIRAD, INRAE, Institut Agro, Montpellier, France; (charlotte.tollenaere@ird.fr)The rice yellow mottle virus (RYMV), genus Sobemovirus, family Solemoviridae constitutes a threat to the actual development of rice cultivation in Africa, inducing severe yield losses in all types of rice growing systems (1). While RYMV is a model in plant virus molecular epidemiology (2,3), the patterns of viral incidence and viral diversity at local geographical scale were much less described to date. This study includes a five-years monitoring of RYMV incidence in six sites, characterized by two rice growing systems (irrigated vs. rainfed lowland), in western Burkina Faso. This allows confirming the highly local patterns of prevalence, and to identify a disease hotspot. A screening of RYMV genetic diversity was then performed in this site though Coat Protein sequencing (132 samples). We found a very high genetic diversity, with the co-occurrence of four distinct lineages at small geographical scale (within one irrigated perimeter, 1100ha). One isolate from each group was fully sequenced (four complete genomes), revealing that one of these lineages results from a recombination event between two others. Temporal dynamics suggest an evolution of RYMV population (modifications in the relative frequencies of each genetic lineage) within the studied period (2015-2019). Then, in controlled conditions, we evaluated the virulence of viral isolates from each genetic group on a set of rice cultivars, including the three most frequently grown in western Burkina Faso. Induced symptoms, as well as viral load (estimated though quantitative PCR) were affected by the rice cultivar, the viral isolate and their interactions. The implications of these results, and potential consequences for the evolution of viral population, are discussed. The perspectives include taking into account multiple isolate infections and potential within-plant competition between the genetic lineages in this system.References(1) Hébrard, E. et al (2021) Encyclopedia of Virology 4th Edition, Bamford, D.H. and Zuckerman, M. Oxford: Academic Press 675–680.(2) Trovão N.S. et al (2015). Virus Evol. 16 :1(3) Rakotomalala M et al (2019). Virus Evol. 1 :5