Sequence characterization of Dasheen mosaic virus isolates from cocoyam in Nicaragua.

Dasheen mosaic virus (DsMV) is an important constraint to production of cocoyam (Xanthosoma spp.) in Nicaragua. Reverse transcription polymerase chain reaction was used to amplify the coat protein (CP) region from ten Nicaraguan DsMV isolates. These isolates showed high nucleotide identity to DsMV isolates from the USA, eastern Asia and Australasia. All Nicaraguan isolates except one shared a tandem repeat in the N-terminus of the CP. Phylogenetic analyses showed that the Nicaraguan isolates formed two distinct subgroups correlated with geographic origin. This can be explained by different origins of the cocoyam genotypes grown in these regions.

The complete genome sequence for a Turkish isolate of Wheat dwarf virus (WDV) from barley confirms the presence of two distinct WDV strains.

The complete genome for a barley isolate of Wheat dwarf virus (WDV) from Tekirdag, Turkey, WDV-Bar[TR], was isolated and sequenced. The genome was found to be 2739 nucleotides long, which is shorter than wheat-infecting WDV isolates, and with a genome organization typical for mastreviruses. The complete genome of WDV-Bar[TR] showed 83-84% nucleotide identity to wheat isolates of WDV, with the non-coding regions SIR and LIR least conserved (72-74% identity). The deduced amino acid sequences for Rep and RepA were most conserved (92-93%), while CP and MP were less conserved (87% and 79-80%, respectively). The identity to other mastrevirus species was significantly lower. In phylogenetic analyses, the WDV isolates formed a distinct clade, well separated from the other mastreviruses with the wheat isolates grouping closely together. Phylogenetic analyses of WDV-Bar[TR], the partial sequence for another Turkish barley isolate (WDV-Bar[TR2]) and published WDV sequences further supported the division of WDV into two distinct strains. The barley strain could also be divided into three subtypes based on relationships and geographic origin. This study shows the first complete published sequence for a barley isolate of WDV.