127
July 1974
Family: Tombusviridae
Genus: Carmovirus
Species: Elderberry latent virus
Acronym: ElLV


Elderberry latent virus

A. T. Jones
Scottish Horticultural Research Institute, Invergowrie, Dundee, Scotland

Contents

Introduction
Main Diseases
Geographical Distribution
Host Range and Symptomatology
Strains
Transmission by Vectors
Transmission through Seed
Transmission by Grafting
Transmission by Dodder
Serology
Nucleic Acid Hybridization
Relationships
Stability in Sap
Purification
Properties of Particles
Particle Structure
Particle Composition
Properties of Infective Nucleic Acid
Molecular Structure
Genome Properties
Satellites
Relations with Cells and Tissues
Ecology and Control
Notes
References
Acknowledgements
Figures

Introduction

Described by Jones (1972).

Synonym

Elderberry virus B (Jones & Murant, 1971)

An RNA-containing virus found only in American elder (Sambucus canadensis) from eastern USA. The infective particles are isometric, c. 30 nm in diameter. The virus is readily sap-transmissible to several herbaceous species. Its vector is unknown.

Main Diseases

Causes line-pattern symptoms in American elder (Sambucus canadensis) (Fig.1, Fig.2), which develops symptoms following mechanical inoculation only when kept in cool conditions. The virus appears to cause no symptoms in experimentally infected S. nigra.

Geographical Distribution

Eastern USA.

Host Range and Symptomatology

Found in naturally infected Sambucus canadensis cv. Adams No. 2 imported into UK from USA. Probably other cultivars in USA also contain the virus but its presence may be masked by nepoviruses (Jones, 1972). In limited host range studies it infected 25 species in the families Amaranthaceae, Chenopodiaceae, Cucurbitaceae and Solanaceae. Almost all plants were infected symptomlessly and many became infected only in inoculated leaves.

Diagnostic species

Chenopodium quinoa. Large chlorotic local lesions 10-14 days after inoculation, coalescing to produce a general chlorosis of inoculated leaves (Fig.4); occasionally, systemic chlorotic or necrotic spots develop (Fig.3).

Symptomless systemic infection occurs in Nicotiana clevelandii, N. tabacum cv. Xanthi-nc and Petunia hybrida.

Propagation species

Chenopodium quinoa. Nicotiana clevelandii is useful for maintaining cultures.

Assay species

No satisfactory assay species found. Assays can be made by determining the maximum infective dilution of preparations in Chenopodium quinoa; suitable dilutions of inoculum sometimes induce countable local lesions in C. quinoa leaves.

Strains

No information.

Transmission by Vectors

No vector reported. The aphids Macrosiphum euphorbiae and Myzus persicae did not transmit the virus from Chenopodium quinoa to C. quinoa when allowed 5, 30 or 180 min acquisition access periods (Jones, 1972).

Transmission through Seed

No information.

Transmission by Dodder

No information.

Serology

The virus is moderately immunogenic giving antiserum with gel-diffusion titres of 1/512. Reacts well in micro-precipitin tests or in gel-diffusion tests in 1% agar. It produces a single line of precipitation in gel-diffusion tests.

Relationships

No serological reaction was obtained with antisera to any of thirty-one distinct isometric viruses and the virus seems distinct from previously described viruses (Jones, 1972 and unpublished). Its particle size, physical properties and the sizes of its RNA and protein molecules are similar to those reported for tomato bushy stunt virus (Martelli, Quacquarelli & Russo, 1971), but the two viruses are unrelated serologically, have different sedimentation coefficients, and possibly differ in the number and arrangement of their coat polypeptides (Mayo & Jones, 1973).

Stability in Sap

In Chenopodium quinoa sap, the virus lost infectivity after 10 min at 85-90°C, storage at room temperature for 7 days, or dilution to 10-5 - 10-6 (Jones, 1972). Most of its infectivity is lost after 10 min at 65°C.

Purification

The virus is easily purified from inoculated Chenopodium quinoa leaves by chloroform clarification of leaf extracts followed by precipitation of the virus at pH 4.8 and differential centrifugation; treatment with n-butanol causes much loss of infectivity (Jones, 1972).

Properties of Particles

Purified preparations sediment as a major infective component (B) and a minor non-infective component (T).

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: When centrifuged to equilibrium 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).

Particle Structure

Particles are disrupted in 2% sodium phosphotungstate but in uranyl formate (Fig.6, Fig.7) they are isometric with diameters of about 17 nm (T) or 30 nm (B). Particles are not penetrated by the stain (Jones, 1972). Calculations based on the M. Wt of the protein and RNA components suggest that the B component may contain 120 protein subunits (Mayo & Jones, 1973).

Particle Composition

Nucleic acid: RNA, single-stranded (Jones, 1972), about 23% of B particle weight. M. Wt, estimated from polyacrylamide gel electrophoresis, is 1.55 x 106 (Mayo & Jones, 1973).

Protein: In polyacrylamide gels the protein from B particles migrated as a single major component with an estimated M. Wt of 40,000 (Mayo & Jones, 1973).

Relations with Cells and Tissues

No information.

Notes

Because the virus caused no symptoms in S. canadensis or S. nigra after 18 months in a heated glasshouse it was called elderberry latent virus (Jones, 1972). However, in cooler conditions leaves of infected plants of S. canadensis, but not S. nigra, develop line-pattern symptoms.

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 and tobacco necrosis viruses do not infect C. quinoa systemically. All are serologically unrelated to elderberry latent virus.

References

  1. Jones & Murant, Rep. Scott. hort. Res. Inst. 1970: 54, 1971.
  2. Jones, Ann. appl. Biol. 70: 49, 1972.
  3. Martelli, Quacquarelli & Russo, CMI/AAB Descriptions of Plant Viruses 69, 4 pp.,1971.
  4. Mayo & Jones, J. gen. Virol. 19: 245, 1973.


Figure 1

Line-pattern symptom in leaflets of experimentally infected Sambucus canadensis.

Figure 2

Line-pattern symptom in leaflets of experimentally infected Sambucus canadensis.

Figure 3

Systemic chlorotic and necrotic spots induced in C. quinoa.

Figure 4

Yellowing in Chenopodium quinoa leaf resulting from the coalescing of chlorotic local lesions.

Figure 5

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.

Figure 6

Particles in uranyl formate; 112 S particles. Bar represents 100 nm.

Figure 7

Particles in uranyl formate; 48 S and 112 S particles. Bar represents 100 nm.