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Reconstructing the history of maize streak virus strain a dispersal to reveal diversification hot spots and its origin in Southern Africa

Monjane A.L., Harkins G.W., Martin D.P., Lemey P., Lefeuvre P., Shepherd D.N., Oluwafemi S., Simuyandi M., Zinga I., Komba E.K., Lakoutene D.P., Mandakombo N., Mboukoulida J., Semballa S., Tagne A., Tiendrebeogo F., Erdmann J.B., Van Antwerpen T., Owor B.E., Flett B., Ramusi M., Windram O.P., Lett J.M., Briddon R.W., Markham P.G., Rybicki E.P., Varsani A.. 2011. Journal of Virology, 85 (18) : p. 9623-9636.

Maize streak virus strain A (MSV-A), the causal agent of maize streak disease, is today one of the most serious biotic threats to African food security. Determining where MSV-A originated and how it spread transcontinentally could yield valuable insights into its historical emergence as a crop pathogen. Similarly, determining where the major extant MSV-A lineages arose could identify geographical hot spots of MSV evolution. Here, we use model-based phylogeographic analyses of 353 fully sequenced MSV-A isolates to reconstruct a plausible history of MSV-A movements over the past 150 years. We show that since the probable emergence of MSV-A in southern Africa around 1863, the virus spread transcontinentally at an average rate of 32.5 km/year (95% highest probability density interval, 15.6 to 51.6 km/year). Using distinctive patterns of nucleotide variation caused by 20 unique intra-MSV-A recombination events, we tentatively classified the MSV-A isolates into 24 easily discernible lineages. Despite many of these lineages displaying distinct geographical distributions, it is apparent that almost all have emerged within the past 4 decades from either southern or east-central Africa. Collectively, our results suggest that regular analysis of MSV-A genomes within these diversification hot spots could be used to monitor the emergence of future MSV-A lineages that could affect maize cultivation in Africa. (Résumé d'auteur)

Mots-clés : plante alimentaire; géminivirus striure du maïs; afrique; afrique du sud; maize streak virus

Thématique : Maladies des plantes

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