316
December 1986
Family: Potyviridae
Genus: Potyvirus
Species: Potato virus V
Acronym: PVV


Potato virus V

R. A. C. Jones
MAFF Harpenden Laboratory, Hatching Green, Harpenden, Hertfordshire, UK, AL5 2BD

C. E. Fribourg
Dpto de Fitopatologiá, Universidad Nacional Agraria, Apartado 456, Lima, Perú

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 in detail by Fribourg & Nakashima (1984). The virus was first reported by Rozendaal et al. (1971) but mistakenly categorized as a deviating strain of potato virus Y, strain C. Also recorded under the names potato virus Y, strain CAB (Calvert et al., 1980) and potato virus Y, strain B (Boudazin et al., 1984).

A virus with flexuous elongated particles c. 760 nm in length. It is readily sap-transmissible and has a narrow host range. Transmitted by aphids in the non-persistent manner. Found in the Andean region of South America and in Western Europe.

Main Diseases

Most cultivars of potato (Solanum tuberosum) react hypersensitively to inoculation developing local necrotic spots (Fig.1) and severe systemic necrosis (Fig.2), and are rarely found infected in the field. In the majority of the small number of cultivars in which natural infection is often found, the virus occurs virtually symptomlessly or induces little more than leaf pallor, some decrease in leaflet size and slight leaflet distortion. However, a few of these cultivars develop mosaic (Fig.3) and necrotic spotting of lower leaves (Calvert et al., 1980; Fribourg & Nakashima, 1984; Jones & Fuller, 1984; Jones, 1987).

Geographical Distribution

Reported so far from Peru, France, the Netherlands and the UK. Widespread only in a limited range of potato cultivars.

Host Range and Symptomatology

Natural infection has been detected only in potato. Except for a few chenopodiaceous species which react with local lesions, the host range is restricted to the Solanaceae. No infection was obtained by sap inoculation of 31 species in ten other families (Calvert et al., 1980; Fribourg & Nakashima, 1984; Jones & Fuller, 1984).

Diagnostic species

Nicotiana clevelandii and N. glutinosa. Systemic vein clearing, vein banding and mosaic.

N. debneyi. Diffuse chlorotic spots in inoculated leaves. Systemic vein clearing, vein banding, mosaic, and chlorotic spots and rings (Fig.4).

N. occidentalis. Systemic vein clearing, vein banding and mosaic.

N. tabacum (tobacco) cv. White Burley. Faint systemic vein clearing, chlorotic spotting, mosaic and vein banding.

Solanum tuberosum (potato). Diagnostic cultivars include Estima and Desiree which develop faint mosaic and mottle respectively, and Maris Piper and Pentland Crown which develop necrotic spots in inoculated leaves (Fig.1) and severe systemic necrosis.

Propagation species

N. occidentalis, N. debneyi and tobacco cv. White Burley are suitable hosts for maintaining the virus and are good sources of virus for purification. Young N. occidentalis seedlings are suitable for aphid transmission tests (Fribourg & Nakashima, 1984).

Assay species

Whole plant assays can be done with N. clevelandii, N. debneyi or N. glutinosa.

Strains

None reported.

Transmission by Vectors

Transmitted by the aphid Myzus persicae after acquisition access periods of 15-30 sec and inoculation access times of 15 min (Fribourg & Nakashima, 1984). Also transmitted in the non-persistent manner by the aphids Brachycaudus helichrysi, Macrosiphum euphorbiae and Rhopalosiphoninus latysiphon (Calvert et al., 1980; Bell, 1982, 1983).

Transmission through Seed

None reported.

Serology

This virus is moderately immunogenic; antisera were obtained with titres of up to 1/4096 in microprecipitin tests (Fribourg & Nakashima, 1984; C. A. Dolby & R. A. C. Jones, unpublished results). Flocculent precipitates are formed in microprecipitin tests. The antisera work well in ELISA (Calvert et al., 1980; Jones & Fuller, 1984).

Relationships

The virus is classified in the potyvirus group on the basis of particle morphology, aphid-transmissibility, induction of pinwheel inclusions in infected cells, and serological relationship to three other potyviruses. Using two antisera to potato virus V in microprecipitin tests, Fribourg & Nakashima (1984) reported SDI values of 4-6 with wild potato mosaic virus, 7.5 with potato virus A and 8.5-10.5 with potato virus Y strains.

Stability in Sap

In N. debneyi sap the virus is inactivated by heating to 55-60°C for 10 min or by dilution beyond 5 x 10-3 (Calvert et al., 1980).

Purification

The following method is effective (Fribourg & Nakashima, 1984). Homogenize N. occidentalis leaves in 0.2 M phosphate buffer, pH 8, containing 0.15% 2-mercaptoethanol and 0.01 M EDTA (1 g leaf tissue: 2 ml buffer). Centrifuge at low speed, stir supernatant fluid for 3 h at 4°C with Triton X-100 (1%, v/v) and then precipitate the virus by adding polyethylene glycol, M. Wt 6000, to 4% (w/v) and NaCl to 0.2 M. Centrifuge at low speed and disperse the pellet by shaking in 0.2 M phosphate buffer, pH 8, containing 1% Triton X-100. After a further low speed centrifugation to remove insoluble material, concentrate the virus by two cycles of differential centrifugation and resuspend the final pellet in 0.01 M phosphate buffer, pH 7.3.

Properties of Particles

A260/A280: 1.31-1.35. The value obtained for a preparation after rate zonal centrifugation in a sucrose gradient was 1.25 (Fribourg & Nakashima, 1984).

Particle Structure

Particles are flexuous filaments with a modal length of c. 760 nm (Fig.6).

Particle Composition

No reports.

Relations with Cells and Tissues

The virus induces characteristic cytoplasmic inclusions. In the electron microscope they appear as pinwheels in thin sections (Fig.5).

Notes

In standard solanaceous test plants, potato virus V induces symptoms that are difficult to distinguish from those of the ordinary and C strains of potato virus Y. However, it can be differentiated readily by serology. It was originally confused with the C strain of potato virus Y (Rozendaal et al., 1971; De Bokx et al., 1975; Calvert et al., 1980) because it induced a strong hypersensitive reaction in potato cultivars known to carry gene Nc. However, such cultivars were later found also to contain a different hypersensitivity gene specific for potato virus V (Fribourg & Nakashima, 1984; Jones, 1987; R. A. C. Jones, unpublished results).

References

  1. Bell, Rec. agric. Res. (Dep. Agric. N. Ireland) 30: 1, 1982.
  2. Bell, Ann. appl. Biol. 102: 1, 1983.
  3. Boudazin, Corre & Maury, Potato Res. 27: 100, 1984.
  4. Calvert, Cooper & McClure, Rec. agric. Res. (Dep. Agric. N. Ireland) 28: 63, 1980.
  5. De Bokx, Kratchanova & Maat, Potato Res. 18: 38, 1975.
  6. Fribourg & Nakashima, Phytopathology 74: 1363, 1984.
  7. Jones, EPPO Bull. 17: 61, 1987.
  8. Jones & Fuller, Pl. Path. 33: 595, 1984.
  9. Rozendaal, Van Binsbergen, Anema, Van Slogteren & Burt, Potato Res. 14: 241, 1971.


Figure 1

Local necrotic spots in inoculated leaf of potato cv. Maris Piper.

Figure 2

Systemic necrosis induced by PVV (right) and symptomless infection with potato virus Y tobacco veinal necrosis strain (left) following graft-inoculation of potato cv. Foxton.

Figure 3

Mild mosaic and crinkling in leaf of potato cv. Wauseon.

Figure 4

Systemic chlorotic rings in leaf of Nicotiana debneyi.

Figure 5

Electron micrograph of pinwheel inclusions in section of leaf of N. occidentalis. Bar represents 500 nm.

Figure 6

Electron micrograph of virus particles from a purified preparation. Bar represents 200 nm.