Abstract:
Rice yellow mottle virus (RYMV) has persisted as a major biotic constraint to rice production in Africa. However,
no data on RYMV epidemics were available in Ghana, although it is an intensive rice-producing country. Surveys
were performed from 2010 to 2020 in eleven rice-growing regions of Ghana. Symptom observations and sero logical detections confirmed that RYMV is circulating in most of these regions. Coat protein gene and complete
genome sequencings revealed that RYMV in Ghana almost exclusively belongs to the strain S2, one of the strains
covering the largest area in West Africa. We also detected the presence of the S1ca strain which is being reported
for the first time outside its area of origin. These results suggested a complex epidemiological history of RYMV in
Ghana and a recent expansion of S1ca to West Africa. Phylogeographic analyses reconstructed at least five in dependent RYMV introductions in Ghana for the last 40 years, probably due to rice cultivation intensification in
West Africa leading to a better circulation of RYMV. In addition to identifying some routes of RYMV dispersion in
Ghana, this study contributes to the epidemiological surveillance of RYMV and helps to design disease management strategies, especially through breeding for rice disease resistance.