Molecular identification and infectivity assay for a barley strain of wheat dwarf virus in barley and wheat

Yellowing and dwarfing disease in wheat (Triticum aestivum) and barley (Hordeum vulgaris) plants is a major constraint for yield production worldwide. Wheat and barley strains of wheat dwarf virus (WDV) were found to be associated with the disease in Iran and some parts of the world. However, host specificity of wheat and barley strains of WDV is controversial. In this study, we isolated and sequenced a new variant of WDV from barley plants in the southwest of Iran. The full-length genome of this isolate comprises 2,732 nucleotides with four open reading frames. Sequence analysis of the full-length genome revealed that this isolate is similar (87.3 to 97% identity) to the barley isolates of WDV and was considered as a new variant of the virus. Phylogenetic analysis indicated that this isolate is grouped with other barley isolates of WDV from Europe in a distinct sub-group with a barley isolate from Iran. An infectious clone of WDV was constructed in a binary vector using a partial dimer of the full-length genome. Agroinoculation with the cloned viral DNA resulted in yellowing and dwarfing symptom in both wheat and barley plants. Using this system, the barley isolate of WDV infects wheat and barley with similar efficiency. This infectious clone can be used for screening both wheat and barley plants for resistance/susceptibility, identification of host resistance gene/s and investigating the virus-host interaction.