Sequence characterization of Barley yellow dwarf virus – OYV

Abstract: Barley yellow dwarf (BYD)-associated viruses are economically important in a wide range of cereals and grasses worldwide. These viruses belong to family Luteoviridae and are efficiently transmitted by aphids in a circulative and non-propagative manner. BYD-associated viruses have a genome of single-stranded positive sense RNA (+ssRNA). Even if isolates of BYD-associated viruses from different parts of the world show significant divergence in pathogenicity and genetic structure, the evolutionary process and the genomic structure of new viral species are poorly known. In this study, BYDV-OYV, which has been proposed to be a distinct tentative virus species and infects oat (Avena sativa), Triticale and grasses in Sweden and Latvia, was investigated to characterize its genomic structure and relationship with other members of family Luteoviridae. To address these issues, a partial region of the BYDV-OYV genome was determined for one Swedish isolate. The sequence consisted of 2,792 nucleotides and contained 4 open reading frames and 3 un-translated regions. The genomic structure of BYDV-OYV resembled those of other species in family Luteoviridae. Sequence comparisons including 15 isolates of the genera Luteovirus and Polerovirus, showed that BYDV-OYV shared highest nucleotide identity with BYDV-PAV-CN (AY855920), BYDV-PAV isolate 05ZZ4 (EU332321), BYDV-PAV isolate 05ZZ13 (EU332327) and BYDV-PAV isolate 05GG5 (EU332310) at 82.8%, 82.6%, 82.6% and 82.5%, respectively. A phylogenetic analysis confirmed that BYDV-OYV is related to other viruses in the genus Luteovirus, but that it is separate from the other known luteoviruses. The deduced amino acid sequence identity of ORF3 (coat protein) between BYDV-OYV and BYDV-PAV-CN was only 87%. Thus, BYDV-OYV should be regarded as a species distinct from BYDV-PAV-CN.