keywords: Epidemiology, host range, molecular characterization, symptomatology
Rice is the primary and secondary host of many viruses, but the most important in Africa is the rice yellow mottle virus (RYMV) genus Sobemovirus. It is endemic in the continent and became important after the introduction of new high yielding exotic varieties from Asia that are susceptible to the virus. The pathogen was first noticed in 1966 in Kenya but it has since spread to other parts of Africa countries. It is environmentally stable, highly infectious and about six strains of the virus now exist. Transmitted both mechanically and by insect vectors belonging to the families Chrysomelidae (Chaetocnema spp., Dactylispa spp., Hispa unsambarica Weise, Sesselia pusilla Gartucker, Trichispa sericea Guerin); Tettigonidae (Conocephalus longipennis de Haan, C. merumontamus Sjostedt) and Coccinelidane (Chnootriba similis Thunberg). Yield losses caused by the virus range from 25 to 100%. Integrated pest management and breeding for resistant varieties are the best strategies so far suggested to reduce havoc caused by this pathogen to rice. This paper reviews the economic importance, distribution, host range, symptom, transmission, varietal reaction, yield loss assessment, epidemiology, molecular characteristics, management strategies and future research needs of the virus.
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