Details of DPV and References

DPV NO: 37 October 1970

Family: Potyviridae

Genus: Potyvirus

Species: Potato virus Y | Acronym: PVY

There is a more recent description of this virus: DPV 242

Potato virus Y

S. Delgado-Sanchez Instituto Nacional de Investigaciones Agricolas, Apdo. Postal No. 6-882, Mexico 6, D. F. Mexico

R. G. Grogan Dept. of Plant Pathology, Univ. of California, Davis, California 95616, USA

Contents

Introduction

Described by Smith (1931).

Selected synonyms

Potato acropetal necrosis virus (Rev. appl. Mycol. 10: 745)

Tobacco vein-banding virus (Rev. appl. Mycol. 10: 60)

Tobacco veinal necrosis virus (Rev. appl. Mycol. 31: 201)

Solanum virus 2 (Rev. appl. Mycol. 17: 52)

Marmor upsilon (Rev. appl. Mycol. 28: 514)

A virus with flexuous helically constructed particles, 730 x 11 nm, sap-transmissible to a narrow range of hosts and transmitted by several species of aphids in the non-persistent manner. It causes important economic diseases of solanaceous plants and has a world-wide distribution.

Main Diseases

In potato it usually causes ‘leaf-drop streak’ or necrosis along the veins of the underside of leaflets in the first year of infection (Fig. 3, Fig. 4); in combination with potato virus X it causes the disease called ‘rugose mosaic’ in the USA, one of the most destructive diseases of potato. In Britain, the term, rugose mosaic, is used to refer to disease caused by potato virus Y in the second and subsequent years of infection. In tobacco, pepper, and tomato the virus causes mild to severe mottling depending on the strain (Smith, 1957).

Geographical Distribution

World-wide.

Host Range and Symptomatology

Reported to infect at least 60 plant spp., mostly in the Solanaceae, but also infects members of the Chenopodiaceae and Leguminosae (Thornberry, 1966).

Diagnostic species

Capsicum frutescens cv. Tabasco (pepper). Mild to severe mottle; no wilting like that caused by tobacco etch virus.

Datura stramonium. Immune to infection by all tested strains of potato virus Y, but susceptible to tobacco etch virus; useful for separating potato virus Y from tobacco etch virus.

Nicotiana glutinosa. Mild to severe mottling depending on the strain (Fig. 1).

N. tabacum (tobacco). Most strains produce vein clearing followed by mottling; an exception is the necrotic strain. Combined infection with potato viruses X and Y produces a synergistic ‘spot necrosis’ reaction which has been used to detect the presence of potato virus Y (Darby, Larson & Walker, 1951).

Solanum tuberosum cv. Saco (potato). Some strains produce local necrotic lesions; useful for separating potato virus Y from potato virus X to which Saco is virtually immune (Benson & Hooker, 1960).

Propagation species

N. glutinosa may be used to maintain the virus. N. tabacum cv. Wisconsin Havana 425 is a good source for virus purification.

Assay species

Local lesion hosts include Chenopodium amaranticolor, C. quinoa (Fig. 5), several species of Lycium, Nicandra physalodes, Nicotiana repanda, N. rustica, Physalis floridana, Solanum demissum ‘Y’ (Fig. 2), S. demissum x S. tuberosum ‘A-6’, and S. tuberosum cvs. Saco and U.S.D.A. seedling 41956.

Strains

Several strains can be distinguished on the basis of severity of systemic symptoms in tobacco and other hosts. The following seem the most important:

Common strains: Differentiated by the severity of symptoms in N. glutinosa, P. floridana and potato. Found world-wide (Kahn & Monroe, 1963).

The necrotic or tobacco veinal necrosis strain (Nobrega & Silberschmidt, 1944) produces severe veinal necrosis in tobacco. Source South America.

Potato virus C (Bawden, 1936) differs from others in not being transmitted by Myzus persicae, which is an efficient vector of PVY. Source Australia and England.

Transmission by Vectors

Transmitted in the non-persistent manner by several aphid spp. Myzus persicae is probably the most efficient vector; others are Myzus ornatus, Macrosiphum euphorbiae, Aulacorthum circumflexum, Aphis nasturtii and Aphis gossypii (Kennedy, Day & Eastop, 1962). Young upper leaves of infected potato plants are better sources of virus for aphids than are middle or lower leaves (Bagnall & Bradley, 1958). Adult or later instar apterous aphids have usually been used in transmission experiments and a pre-acquisition starvation period of 2-7 h aids transmission. The optimum acquisition feeding period is from 30 sec to 5 min a period of 30-60 sec to 24 h is satisfactory for inoculation (Bradley, 1953; Easton, Larson & Hougas, 1958).

Transmission through Seed

Not reported.

Transmission by Dodder

Not reported.

Serology

Strongly immunogenic. Emulsification of antigen with Freund’s adjuvant before injecting it intramuscularly into rabbits increased both the titre of the antiserum obtained and the period of maximum immune response (Wetter, 1960). Microprecipitin tests can be done using clarified extracts of infected tissue. The formation of non-specific precipitates can be avoided by buffering the saline solution with 0.05 M Tris-HCl. Serological precipitates in mixed liquids are of the flocculent (flagellar) type.

Relationships

Precipitin tests showed that the common, C and necrotic strains are serologically related (Bawden & Kassanis, 1951), but differences were noted between the homologous and heterologous reactions, particularly between the necrotic and the common strains (Bartels, 1957). Using high titred antisera, PVY was shown to be distantly related to at least 16 other filamentous viruses, and these comprise the potato virus Y group (Brandes & Bercks, 1965).

In cross-protection tests, several mild isolates protected against more virulent isolates in potato, but not in tobacco (Darby et al., 1951).

Stability in Sap

Infectivity is lost after heating sap from infected tobacco for 10 min at 55-60°C; dilution end-points range from 10^-2 to 10^-3 for most isolates; inactivated in vitro within 48-72 h.

Purification

Several procedures have been described, but aggregation of the particles presents difficulties (Van Regenmortel, 1964; Venekamp & Mosch, 1964). A procedure for obtaining essentially unaggregated preparations has been described (Delgado-Sanchez & Grogan, 1966).

Particle Structure

Virus particles are flexuous filaments about 11 nm wide and helically constructed, with a pitch of about 3.3 nm (Varma et al., 1968). The normal length of particles in purified virus preparations is about 684 nm, compared with about 730 nm for particles in tissue-dip preparations (Fig. 6).

Particle Composition

Not known.

Relations with Cells and Tissues

Pin-wheel inclusions (Fig. 8) occur in systemically infected tissue (Edwardson, 1966). They are composed of pin-wheel plates, which are easily seen in leaf-dip preparations (Fig. 7) and have characteristic striations with a spacing of c. 5 nm.

Notes

In some Solanum species the virus may be confused with tobacco etch and henbane mosaic viruses, which produce somewhat similar symptoms and have similar host ranges. Tobacco etch virus, however, infects Datura stramonium and produces necrotic wilting of Tabasco pepper and etching of the leaves of tobacco. Henbane mosaic virus occurs less frequently in the common hosts of potato Y and tobacco etch viruses; it can infect D. stramonium but not Tabasco pepper.

Figures

References list for DPV: Potato virus Y (37)

1. Bagnall & Bradley, Phytopathology 48: 121, 1958.
2. Bartels, Proc. 3rd Conf. on Potato Virus Diseases, Lisse-Wageningen: 13, 1957.
3. Bawden, Ann. appl. Biol. 23: 487, 1936.
4. Bawden & Kassanis, Ann. appl. Biol. 38: 402, 1951.
5. Benson & Hooker, Phytopathology 50: 231, 1960.
6. Bradley, Nature, Lond. 171: 755, 1953.
7. Brandes & Bercks, Adv. Virus Res. 11: 1, 1965.
8. Darby, Larson & Walker, Res. Bull. Univ. Wisc. 177, 32 pp., 1951.
9. Delgado-Sanchez & Grogan, Phytopathology 56: 1397, 1966.
10. Easton, Larson & Hougas, Res. Bull. Univ. Wisc. 205, 32 pp., 1958.
11. Edwardson, Am. J. Bot. 53: 359, 1966.
12. Kahn & Monroe, Phytopathology 53: 1356, 1963.
13. Kennedy, Day & Eastop, A conspectus of aphids as vectors of plant viruses, London, Commonwealth Institute of Entomology, 1962.
14. Nobrega & Silberschmidt, Arquiv. Inst. Biol. S. Paulo 15: 307, 1944.
15. Smith, Proc. R. Soc., B 109: 251, 1931.
16. Smith, A Text Book of Plant Virus Diseases, Churchill, London, 1957.
17. Thornberry, Index of Plant Virus Diseases, Agric. Handb. U.S.D.A., 307, 285, 1966.
18. Van Regenmortel, Virology 23: 495, 1964.
19. Varma, Gibbs, Woods & Finch, J. gen. Virol. 2: 107, 1968.
20. Venekamp & Mosch, Virology 23: 394, 1964.
21. Wetter, Arch. Mikrobiol. 37: 278, 1960.