52
June 1971
Family: Tymoviridae
Genus: Tymovirus
Species: Belladonna mottle virus
Acronym: BeMV


Belladonna mottle virus

H. L. Paul
Biologische Bundesanstalt für Land- und Forstwirtschaft, Institut für landw. Virusforschung, Braunschweig, Germany

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 Bode & Marcus (1959) and Paul et al. (1968).

Synonym

Tollkirschenscheckungs-Virus (Paul et al., 1968)

An RNA-containing virus with isometric particles c. 27 nm in diameter which sediment as two components in the centrifuge. It is readily transmitted by sap inoculation and by the beetle Epithrix atropae, and infects species in the Solanaceae. It is found in Europe.

Main Diseases

Causes mild mottling and sometimes deformation in Atropa belladonna (Fig.1).

Geographical Distribution

Europe. Around Braunschweig (northern Germany) and in the Rila mountains (Bulgaria) (Paul et al., 1968).

Host Range and Symptomatology

122 species in 28 families of dicotyledons have been tested by inoculation of sap. Most species of Solanaceae were infected systemically; the only non-solanaceous host found was Chenopodium quinoa, in which the virus was restricted to the inoculated leaves (Paul et at., 1968). Symptom expression in all hosts is variable.

Diagnostic species

Nicotiana tabacum (tobacco) cvs. Samsun or Xanthi-nc. Inoculated leaves show ring-like necrotic lesions (Fig.4); systemically infected leaves show bright vein-clearing followed by vein-banding (Fig.2, Fig.5) or fine veinal necrosis, and mosaic.

Datura stramonium. Many necrotic lesions in the inoculated leaves; mosaic or irregular chlorotic areas or necrotic line patterns in systemically infected leaves.

Propagation species

Nicotiana tabacum, Datura stramonium.

Assay species

No reliable local lesion host known.

Strains

Variants differ in virulence, in the relative proportions of the two sedimenting components (Paul, 1969), and in sensitivity to mercury-containing compounds (Koenig, 1969).

Transmission by Vectors

An efficient vector is the beetle Epithrix atropae (Jankulowa et al., 1968). Aphids seem not to transmit the virus (Bode & Marcus, 1959).

Transmission through Seed

None found.

Transmission by Dodder

Not tested.

Serology

The virus is strongly immunogenic, antisera with titres of 1/1024 in double diffusion tests are readily obtained. In Ouchterlony tests the formation of bands of precipitate is inhibited by the addition of mercury-containing preservatives e.g. Merthiolate (Koenig, 1969).

Relationships

The serological relationship between the strains is very close. Physical data, RNA base composition, and serological behaviour show that the virus belongs to the Andean potato latent virus subgroup of the turnip yellow mosaic virus group (Jankulowa et al., 1968; Koenig, 1969).

Stability in Sap

The virus is inactivated when heated at 80°C for 10 min; sap of infected plants retains its infectivity at room temperature for 5 days to 3 weeks depending on how soon the sap decomposes. The dilution end-point is 10-6-10-7 (Paul et al., 1968).

Purification

The virus is stable, occurs in high concentrations in sap and can easily be purified. Steere’s chloroform-butanol method of clarification, followed by several cycles of differential centrifugation, gives good virus preparations.

Properties of Particles

(Paul et al., 1968; Paul, 1969). Purified preparations contain two classes of particles, empty non-infective protein shells without RNA (T) and the infective nucleoprotein (B). Sedimentation coefficients (s20,w) at infinite dilution (svedbergs): 53 (T), 113 (B). In most preparations from tobacco the particle ratio T : B is about 1 : 4.

Molecular weights (daltons): 2.2 x 106 (T), 5.2 x 106 (B).

Diffusion coefficients (D20, w x 10-7 cm2 sec-1): 2.3 (T), 1.6 (B).

Partial specific volumes (calculated): 0.74 ml/g (T), 0.69 ml/g (B).

Electrophoretic behaviour: in gels containing various buffers of pH between 6 and 8 the virus migrates as one component towards the cathode (Koenig, 1969).

Absorbance at 260 nm (1 mg/ml, 1 cm light path): about 8 for the normal mixture of T and B components.

A260/A280: 1.82, corrected for light scattering, for the normal mixture of T and B components.

Buoyant density: not determined, but the B component is not homogeneous in CsCl gradients (Paul, 1969).

Particle Structure

The particles are isometric, c. 27 nm in diameter with angular polygonal outlines (Fig.3). The empty shells are penetrated by negative stains used for electron microscopy, whereas the infective particles are not. The virus apparently has a structure similar to that of turnip yellow mosaic virus, i.e. icosahedral symmetry with 32 major morphological subunits (Paul et al., 1968).

Particle Composition

RNA: Single-stranded with a M. Wt of 2.0 x 106. Molar percentage of bases: G17.5±0.3; A22.8±0.2; C32.8±0.3; U26.9±0.2 (Jankulowa et al., 1968). The infective particles contain about 37% RNA, the unfractionated virus preparations about 28% (Paul et al., 1968).

Protein: The subunits have a M. Wt of 20,300 (H. L. Paul & U. Buchta, unpublished), and contain 190-194 amino acid residues. The amino acid composition is (moles %): ala 8.5; arg 2.5; asx 5.6; cys 1.1; glx 8.8; gly 6.9; his 0.0; ile 9.1; leu 9.5; lys 4.9; met 0.9; phe 2.6; pro 8.3; ser 12.5; thr 8.4; try 0.6; tyr 2.1; val 7.7 (Jankulowa et al., 1968).

Relations with Cells and Tissues

The vesicles produced in chloroplasts (Harrison & Roberts, 1970) resemble those caused by turnip yellow mosaic virus in other species.

Notes

Some naturally infected Atropa belladonna plants also contain belladonna mosaic virus (=tobacco rattle virus) (Smith, 1943), potato leafroll virus (O. Bode, unpublished) and atropa mild mosaic virus (Bode, Brandes & Paul, 1969; Harrison & Roberts, 1970), which has filamentous particles about 900 nm long and is transmitted by aphids, such as Myzus persicae, in brief feeding periods.

References

  1. Bode & Marcus, Proc. 4th Internat. Congr. Crop Protection, Hamburg, 1957, 1: 375, 1959.
  2. Bode, Brandes & Paul, Jber. biol. BundAnst. Land- u. Forstw. Braunschweig, 1968: A61, 1969.
  3. Harrison & Roberts, Rep. Scott. hort. Res. Inst. for 1969: 52, 1970.
  4. Jankulowa, Huth, Wittmann & Paul, Phytopath. Z. 63: 177, 1968.
  5. Koenig, Virology 38: 140, 1969.
  6. Paul, Phytopath. Z. 65: 257, 1969.
  7. Paul, Bode, Jankulowa & Brandes, Phytopath. Z. 61: 342, 1968.
  8. Smith, Parasitology 35: 159, 1943.

Acknowledgements

Photographs: courtesy of Institut für landwirtschaftliche Virusforschung, Braunschweig, Germany.


Figure 1

Atropa belladonna leaf, naturally infected.

Figure 2

Infected plant of Nicotiana tabacum cv. Samsun.

Figure 3

Particles in a purified preparation, mounted in uranyl formate. Bar represents 100 nm.

Figure 4

N. tabacum cv. Samsun, inoculated leaf.

Figure 5

N. tabacum cv. Samsun, systemically infected leaf.