Lydiane Bonheur

Molecular characterization of yam virus X, a new potexvirus infecting yams (Dioscorea spp) and evidence for the existence of at least three distinct potexviruses infecting yams

The genome of yam virus X (YVX), a new member of the genus Potexvirus from yam (Dioscorea trifida), was completely sequenced. Structural and phylogenetic analysis showed that the closest relative of YVX is nerine virus X. A prevalence study found YVX only in plants maintained in Guadeloupe and showed that it also infects members of the complex D. cayenensis rotundata. This study provides evidence for the existence of two additional potexviruses, one of which infects D. nummularia in Vanuatu and the other, D. bulbifera and D. rotundata in Haiti and D. trifida and D. rotundata in Guadeloupe. This work also shows that existing potexvirus-specific degenerate primers targeting the ORF1-encoded polymerase domain are well suited for the identification of the three potexviruses reported here.

The genome sequence of Dioscorea bacilliform TR virus, a member of the genus Badnavirus infecting Dioscorea spp., sheds light on the possible function of endogenous Dioscorea bacilliform viruses

The complete genome sequence of Dioscorea bacilliform TR virus (DBTRV) was determined. The closest relatives of DBTRV are Dioscorea bacilliform AL virus (DBALV) and Dioscorea bacilliform RT virus 1 (DBRTV1). Specific primers were designed and used to determine the prevalence of DBTRV in a yam germplasm collection. It was found that this virus infects Dioscorea alata and D. trifida plants in Guadeloupe and French Guyana. DTRBV was not detected in any of the tested D. cayenensis-rotundata accessions. In silico analysis provided evidence for the presence of DBTRV-like endogenous sequences in the genome of D. cayenensis-rotundata, pointing to a possible role of these sequences in antiviral defense.