Species: Elderberry latent virus
|This is a revised version of DPV 127|
A. T. Jones
Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, Scotland.
Host Range and Symptomatology
Transmission by Vectors
Transmission through Seed
Transmission by Grafting
Transmission by Dodder
Nucleic Acid Hybridization
Stability in Sap
Properties of Particles
Properties of Infective Nucleic Acid
Relations with Cells and Tissues
Ecology and Control
Pelargonium ringspot virus (PelRSV; Stone & Hollings, 1975; 1976; Jones, 1983) is indistinguishable from ElLV in many biological and biophysical properties and is closely related serologically (Jones et al., 2000). This description applies equally to ElLV and PelRSV, except where noted otherwise.
An RNA-containing virus reported as ElLV in American elder (Sambucus canadensis) from eastern USA and as PelRSV in pelargonium worldwide. The infective particles are isometric, about 30 nm in diameter. The virus is readily sap-transmissible to several herbaceous species. Its vector is unknown.
No serological reaction was obtained with antisera to any of thirty-one distinct isometric viruses and ElLV seems distinct from other similar viruses including Pelargonium flower break, Pelargonium line pattern and Pelargonium ring pattern viruses (Jones, 1972; Jones et al., 2000). Its particle size, physical properties and the sizes of its RNA and protein molecules are similar to those reported for species in the genus Carmovirus but, because its genome expression strategy differs from that of recognised carmoviruses, it may be better placed in a new genus, together with Pelargonium line pattern and Pelargonium chlorotic ring pattern viruses (Kinard & Jordan, 2002).
Sedimentation coefficients (s°20, w): 48 S (T) and 112 S (B) (Fig.5).
Molecular weight (daltons): about 7 x 106 (B) (Mayo & Jones, 1973).
Isoelectric point: about pH 4.8.
A260/A280: 1.62 (B).
Buoyant density: In CsCl solution, purified preparations of an uncloned isolate formed a major band at 1.36 g/cm3 and a minor band at 1.37 g/cm3 (Mayo & Jones, 1973).
Protein: In polyacrylamide gels the protein from B particles migrated as a single major component with an estimated Mol. Wt of 40,000 (Mayo & Jones, 1973; Jones et al., 2000). However, purified preparations of PelRSV after storage contained an additional species of Mol. Wt 37,000, which is presumably a degradation product of the larger species (Jones et al., 2000). The coat protein sequence deduced from the published gene sequence consists of 338 amino acid residues with a calculated Mol. Wt of 36,678.
DsRNA analysis of infected plants detected up to three dsRNA species (Kinard et al., 1996; Jones et al., 2000; Kinard & Jordan, 2002). The largest, of 3.7 - 4.0 kbp, would correspond to the genomic RNA and the smallest, of about 1.8 kbp, which was not detected consistently (Jones et al., 2000), is presumably the replicative form of the sub-genomic RNA species. The third dsRNA species, of about 2.6 kbp, was detected by Jones et al. (2000) but not by Kinard et al. (1996) or Kinard & Jordan (2002), and is of unknown origin.
Kinard & Jordan (2002) suggest that the genome organisation of ElLV is similar to that of carmoviruses. The two 5'-most ORFs, coding for polymerase and polymerase readthrough proteins, are probably translated from the genomic RNA. However, unlike definitive carmoviruses, only one subgenomic RNA species has been detected for ElLV and all three downstream ORFs, coding for p7, p9 and coat protein, must presumably be translated from this RNA.
The virus is distinct from other isometric viruses found in elder: the nepoviruses (arabis mosaic, cherry leaf roll, strawberry latent ringspot, tobacco ringspot and tomato ringspot) induce characteristic symptoms in Chenopodium quinoa and cucumber and have a different sedimentation behaviour; Cucumber mosaic virus and Tobacco necrosis virus do not infect C. quinoa systemically. All are serologically unrelated to ElLV.
ElLV and PelRSV are sufficiently similar to be regarded as strains of a single virus species, except for the reported differences in their nucleotide and aminoacid sequences. However, until the sequences are published, it is difficult to evaluate these differences. Likewise, availability of the sequence data should help in deciding whether the virus(es) should be placed in the genus Carmovirus or in a new genus in the Tombusviridae.
Line-pattern symptom in leaflets of experimentally infected Sambucus canadensis.
Line-pattern symptom in leaflet of experimentally infected Sambucus canadensis.
Systemic chlorotic and necrotic spots induced in C. quinoa.
Yellowing in Chenopodium quinoa leaf resulting from the coalescing of chlorotic local lesions.
Sedimentation pattern produced by a partially purified virus preparation showing the minor 48 S component and the 112 S component. Sedimentation is from left to right.
112S particles in uranyl formate. Bar represents 100 nm.
Particles in uranyl formate showing the 48 S and 112 S particles. Bar represents 100 nm.