Details of DPV and References

DPV NO: 21 October 1970

Family: Tombusviridae

Genus: Dianthovirus

Species: Carnation ringspot virus | Acronym: CRSV

There is a more recent description of this virus: DPV 308

Carnation ringspot virus

M. Hollings Glasshouse Crops Research Institute, Littlehampton, Sussex, England

Olwen M. Stone Glasshouse Crops Research Institute, Littlehampton, Sussex, England

Contents

Introduction

Described by Kassanis (1955).

Synonym

Anjermozaïek virus (Rev. appl. Mycol. 31: 122)

An RNA-containing virus with isometric particles about 30 nm in diameter, transmissible by foliage contact and by inoculation of sap. It occurs naturally only in species of Caryophyllaceae, but can be transmitted experimentally to other species; reported to be transmitted by two nematode genera and by root contact. Widespread, but common only in badly managed carnation crops.

Main Diseases

Leaf mottle, ringspots, stunting and distortion in carnation and Dianthus barbatus (sweet william), sometimes with leaf-tip necrosis (Fig. 1, Fig. 3). Flowers distorted and of poor quality (Fig. 2).

Geographical Distribution

Found wherever carnations are grown in temperate regions.

Host Range and Symptomatology

Over 60 species in 25 dicotyledonous families can be infected when inoculated with purified preparations or sap of infected Nicotiana clevelandii; sap transmission from carnation and Dianthus barbatus is possible only to hosts in the families Caryophyllaceae, Aizoaceae, Chenopodiaceae and Amaranthaceae.

Diagnostic species

Dianthus barbatus. Inoculated leaves show necrotic flecks, rings and ringspots after 4-7 days followed by systemic chlorotic and semi-necrotic rings and flecks. Not all clones show clear symptoms or support large concentrations of virus.

Gomphrena globosa. Local necrotic rings develop in 2-4 days after inoculation (Fig. 6), followed by systemic flecking, mottle and distortion.

Phaseolus vulgaris (French bean). Local chlorotic dots in 4-5 days, becoming white and necrotic; irregular systemic spotting and necrotic veinal flecks, later growth symptomless.

Chenopodium amaranticolor and C. quinoa. Local necrotic lesions in 2-4 days (Fig. 5); usually not systemic.

Tetragonia expansa. Local white necrotic dots in 2-3 days, sometimes followed by systemic chlorotic flecks.

Vigna sinensis (cowpea). Local necrotic lesions in 2-4 days (Fig. 4).

Propagation species

Dianthus barbatus is a suitable host for maintaining cultures.

Nicotiana clevelandii is the best source for purification, though Phaseolus vulgaris and Vigna sinensis have also been used.

Assay species

Chenopodium amaranticolor, C. quinoa, and Vigna sinensis are useful local lesion hosts.

Strains

No strain differences reported.

Transmission by Vectors

Transmission reported by adult nematodes of Longidorus macrosoma and Xiphinema diversicaudatum (Fritzsche & Schmelzer, 1967).

Transmission through Seed

Not found.

Transmission by Dodder

Apparently not tested.

Serology

The virus is a good immunogen, and rabbits immunized by one intravenous plus two intramuscular injections gave antisera with specific titres in precipitin tube tests of 1/4096 to 1/32,768. The virus reacts well both in precipitin tube and in gel-diffusion tests and can be detected in crude sap of carnation by gel-diffusion tests provided that the virus concentration is high (high temperature or the presence of other viruses can depress the concentration). Specific precipitates in tubes are granular (somatic) and a single band of precipitate forms in gel-diffusion tests. In immunoelectrophoresis tests at pH 8.6 (Devergne & Cardin, 1967) the virus moves to the cathode and two bands of precipitate are formed; this may be due to partial degradation of the virus.

Relationships

Carnation ringspot virus does not react with antisera to about 35 other isometric viruses.

Stability in Sap

In sap of Dianthus barbatus the thermal inactivation point (10 min) is about 80°C though much infectivity is lost above 60°C; dilution end point is 10^-5 and infectivity is retained at 20°C for 50-60 days. In lyophilized sap of Nicotiana clevelandii the virus retained infectivity at room temperature, under vacuum, for over 6 years.

Purification

Systemically infected Nicotiana clevelandii leaves yield the most virus; the method used by Hollings & Stone (1965) gives pure concentrated preparations. Plants are minced with phosphate buffer (pH 7.6) containing 0.1% thioglycollic acid (wt/vol=1/1.25), the sap extracted, n-butanol added to 8.5% of the total volume, and the mixture stored overnight at 2°C. The virus is then separated by differential centrifugation. The virus may also be purified by precipitation with ammonium sulphate (40% saturation) or by acid precipitation (pH 4.8).

Properties of Particles

Sedimentation coefficient (s_20,w): c. 135 S. No accessory viral components are found by analytical ultra-centrifugation.

Molecular weight: 7.07 x 10⁶ (Kalmakoff & Tremaine, 1967).

Absorbance at 260 nm (1 mg/ml, 1 cm light path): 6.46.

Particle Structure

Particles are rounded, isometric and about 30 nm in diameter; the subunit structure is not known. Particles are stable in phosphotungstate (Fig. 7).

Particle Composition

RNA: Molecular weight 1.4 x 10⁶, about 20.5% of the particle weight, probably single stranded. Molar percentages of nucleotides: G26; A27; C23; U24.

Protein: Subunits have molecular weight about 3.8 x 10⁴, and contain about 347 amino-acid residues (Kalmakoff & Tremaine, 1967).

Relations with Cells and Tissues

The virus is found in stems, leaves, flowers and roots and in some of the apical meristems. No inclusion bodies have been observed and sites of synthesis have not been reported.

Notes

Carnation ringspot virus can be readily eliminated from several hosts by heat treatment (37°C for 28 days) and also by meristem-tip culture. It is commonly found in carnation together with carnation mottle virus from which it can be readily distinguished by symptoms in Gomphrena globosa and Dianthus barbatus; the symptoms caused by carnation ringspot virus in carnation cannot readily be confused with those caused by any other carnation virus.

Acknowledgements

Photographs: M. Hollings and Glasshouse Crops Research Institute.

Figures

References list for DPV: Carnation ringspot virus (21)

1. Devergne & Cardin, Annls. Épiphyt. 18: 65, 1967.
2. Fritzsche & Schmelzer, Naturwissenschaften 54: 488, 1967.
3. Hollings & Stone, Ann. appl. Biol. 56: 73, 1965.
4. Kalmakoff & Tremaine, Virology 33: 10, 1967.
5. Kassanis, Ann. appl. Biol. 43: 103, 1955.