Elderberry latent virus: its relationship to Pelargonium ringspot virus and its identification as a distinct member of the genus Carmovirus, family Tombusviridae

The properties of Elderberry latent virus (ELV) and Pelargonium ringspot vi rus (PelRSV) were compared. The viruses were largely indistinguishable in h erbaceous host range and symptomatology, particle morphology, sedimentation coefficient and RNA profiles and size. They were also very closely related serologically with SDI differences in agarose gel double-diffusion tests o f I to 3. Purified virus particle preparations of each virus contained isom etric particles c. 30 nm in diameter that sedimented as a major component w ith an s degrees(20,w) of 112-115S. Purified virus particle preparations co ntained a major and a minor ssRNA species that in polyacrylamide gel electr ophoresis (PAGE) had estimated sizes of c. 3.8 kb and c. 1.6 kb respectivel y. Plants of Chenopodium quinoa infected with ELV or PelRSV each contained three dsRNA species of c. 3.8, 2.6 and 1.8 kbp, although the smallest of th ese species was not evident in ail preparations. Protein from purified viru s particle preparations contained a major polypeptide that, in SDS-PAGE, ha d an estimated M-r of 40 000 (40K). However, after storage of purified viru s particles for 7-10 days, protein preparations from PelRSV particles also contained an additional major polypeptide of estimated M-r of 37 000 that i s probably derived by degradation of the 40K protein; this additional compo nent was not observed in freshly prepared preparations of ELV. Neither viru s was found to be related serologically to 16 other viruses with isometric particles and similar properties. These data, together with the recent find ing by other researchers that the smallest RNA species is a sub-genomic RNA , suggests that both viruses are members of the genus Carmovirus, and that PelRSV is a minor variant of ELV. However, the taxonomic status of these tw o viruses is discussed in relation to recent brief reports comparing the nu cleotide and amino acid sequences of these two viruses.