Genetic diversity among yam mosaic virus (YMV) isolates infecting yam of the complex Dioscorea cayenensis rotundata in Togo

Abstract

Phylogenetic analyses were carried out using partial CP-encoding nucleotide sequences and 3´-UTR of 31 YMV isolates originated from the five major yam-growing areas of Togo (Maritime, Plateaux, Central, Kara and Savannas Regions). The aim of this study is to know the genetic structure of YMV populations in Togo in order to develop yam resistant genotypes against the virus. Three major clusters of YMV isolates were observed. Clustering of the 31 isolates did not correlate with the geographical origin but, isolates from Maritime, Plateaux and Central Regions, were genetically more variable than isolates from Kara and Savannas Regions. Comparison of the 31 isolates of Togo with 15 nucleotide sequences from Genbank and originated from other parts of Africa and Caribbean, showed that few isolates from Togo were close to the isolates belonging to phylogenetic groups I and III of Africa but the majority were rather, genetically different. These results revealed that YMV isolates infecting yams in Togo, are genetically variable and they are different a little from isolates of other African countries, suggesting a high pathogenic potential of YMV populations in the various yam–growing areas of Togo and consequently problems of improved yam varieties introduction in the country.

Keywords: Yam mosaic virus, Dioscorea cayenensis rotundata, molecular variability, genetic group, phylogenetic analysis, yam-growing area