70
October 1971
Family: Potyviridae
Genus: Potyvirus
Species: Plum pox virus
Acronym: PPV


Plum pox virus

H. Kegler
Institut für Phytopathologie Aschersleben der Deutschen Akademie der Landwirtschaftswissenschaften zu Berlin, Germany

Christiane Schade
Lehrstuhl Phytopathologie und Pflanzenschutz der Martin-Luther-Universität Halle, 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 Atanasoff (1932).

Selected synonyms
Prunus virus 7 (Rev. appl. Mycol. 18: 188)
Annulus pruni (Rev. appl. Mycol. 26: 553)
Sarka virus (Rev. appl. Mycol. 31: 335)

An RNA-containing virus with elongated particles c. 764 x 20 nm. It has a restricted host range, is transmitted by several species of aphid in the non-persistent manner and is readily transmissible by inoculation of sap.

Main Diseases

Causes ‘pox’ diseases of plum, apricot and peach.

Geographical Distribution

Europe (especially southeastern Europe), Turkey and, probably, New Zealand.

Host Range and Symptomatology

Only found naturally in the genus Prunus, of which 15 species are known to be susceptible. The most important natural source of infection is P. spinosa, which usually shows no symptoms (Jordovic, Festic & Rankovic, 1969). P. avium, P. cerasus, P. mahaleb and P. triloba are not susceptible (Christoff, 1958; Baumann, 1965). Chenopodium foetidum and Nicotiana clevelandii have been commonly used as herbaceous indicator plants but Van Oosten (1970, 1971) found 60 new host species in 8 plant families out of 180 species (28 families) tested. Among these were several weeds and garden plants including Lamium amplexicaule, Ranunculus arvensis, Solanum nigrum and Zinnia elegans.

Diagnostic species
Prunus domestica (plum) cvs. Pozegaca (‘Kjustendilska sliva’), Hauszwetsche or Grosse Grüne Reneklode show severe diffuse olive-green rings or mottling on the leaves (Fig.1). Fruits of cvs. Pozegaca, Czar and Hauszwetsche develop severe ‘pox’ symptoms (Fig.2), with dark-coloured rings on the skin, brown or reddish discoloration of the flesh and brown spots on the stones. Up to 90% of the fruit falls prematurely. Cvs. Anna Späth, Grosse Grüne Reneklode, Montfort and Stanley show no symptoms on the fruit.

Prunus persica (peach). Vein-yellowing, chlorotic spotting and distortion of the leaves, diffuse yellowish mottling of fruit skin (Schuch, 1962).

Prunus armeniaca (apricot). Diffuse pale green rings and lines on leaves, deformation and necrotic rings on fruits, yellow rings on stones (Németh, 1964).

Chenopodium foetidum. Diffuse yellowish or necrotic local spots (Fig.3) (Németh, 1963). Not systemic.

Ranunculus arvensis. Yellow local lesions and systemic concentric rings (Van Oosten, 1970).

Propagation species
Nicotiana clevelandii, N. megalosiphon.

Assay species
Chenopodium foetidum is a useful local lesion host.

Strains

Some isolates cause severe symptoms in N. clevelandii, whereas others cause almost none (Schade, 1969). Sutic et al. (1971) distinguished three strains by the symptoms they caused in C. foetidum and called them the yellow, necrotic and yellow-necrotic strains.

Transmission by Vectors

Transmitted by the aphids Brachycaudus cardui, B. helichrysi, Phorodon humuli and Myzus persicae in the non-persistent manner (Atanasoff, 1934; Kassanis & Sutic, 1965; Kunze & Krczal, 1971). The disease spreads from infected trees very quickly; 48-100% of the trees within 100 m of an infected tree were infected in 10 years (Jordovic, 1968). Young orchards more than 500 m from infected trees remain healthy.

Transmission through Seed

Not seed-transmitted in plum.

Serology

The virus is a good immunogen. Antisera with titres of 1/4000-1/16,000 are readily obtained. Specific precipitates of virus in serological tests in mixed liquids are bulky and flocculent.

Relationships

The properties of the virus (morphology of particles, vector type, etc.) suggest that it is a member of the potato virus Y group of viruses (Brandes & Wetter, 1959).

Stability in Sap

In Nicotiana clevelandii sap, the thermal inactivation point (10 min) is about 51-54°C (Cropley, 1968), in Chenopodium foetidum sap 40-47°C; dilution end-points are 10-4 and 10-1 respectively; infectivity is retained at 20°C for 1-2 days.

Purification

The choice of virus isolate is important, because isolates differ considerably in concentration in infected tissue. Two methods of purification seem satisfactory:

1. Schade (1969). Homogenize 100 g systemically infected N. clevelandii leaf tissue in 300 ml distilled water containing 0.3% (w/v) ascorbic acid and 0.01 M sodium diethyl dithiocarbamate (DIECA). Shake 5 min with an equal volume of cooled chloroform, centrifuge 15 min at 1000 g and 15 min at 5000 g, retaining the aqueous phase at each step. Concentrate the virus by one cycle of high and low speed centrifugation, resuspending the virus in 0.05 M borate buffer, pH 8.2. Normal plant proteins may be removed by absorption with host-specific antisera.

2. Rankovic & Jordovic (1970). Harvest systemically infected leaves of N. clevelandii 15-20 days after inoculation of the plants, chill at c. 4°C and grind each 100 g leaf in a mixture of 100 ml 0.02 M phosphate buffer pH 7.0 containing 0.01 M DIECA and 0.02 M thioglycollate, plus 15 ml diethyl ether and 15 ml carbon tetrachloride. Centrifuge for 10 min at 2000 g, retain the aqueous phase and concentrate the virus by two cycles of differential centrifugation followed by centrifugation in sucrose density gradients.

Properties of Particles

No information.

Particle Structure

Particles are filamentous (Fig.4), c. 760 nm long and 20 nm wide (Kegler, Schmidt & Trifonow, 1964) or c. 725-750 nm long (Babovic, Sutic & Bode, 1971).

Particle Composition

No information.

Relations with Cells and Tissues

During the growing season the terminal buds of quickly-growing shoots are mostly virus-free (Trifonow, 1969). Needle-shaped inclusions and X-bodies are abundant in the nucleus and in the cytoplasm of cells of systemically infected herbaceous hosts such as Nicotiana clevelandii (Plese, Pilovic & Wrischer, 1969) and in the leaves and ripe fruits of infected plum and peach trees. They seem to be of diagnostic value for differentiating plum pox and pseudo-pox diseases (Van Oosten & Bakel, 1970). ‘Pin-wheel’ inclusions occur in leaf cells of plum, peach and Chenopodium foetidum (Bovey, 1971).

Notes

The symptoms in plum caused by plum pox, pseudo-pox (narrow striped variegation) and plum line pattern viruses may sometimes be very similar. Mixed infection with viruses of the prunus necrotic ringspot/prune dwarf type is common. To distinguish between these viruses several test plants must be used; the following are recommended:

Hosts Virus
Plum
pox
Plum
pseudo-
pox
Plum
line
pattern
Prunus
necrotic
ringspot
Celosia argentea - + - -
Chenopodium foetidum + - - -
Prunus avium seedling - - + +
P. domestica cv. Pozegaca + + + -
P. serrulata cv. Shirofugen - - - +
+ = symptoms; - = no symptoms

References

  1. Atanasoff, Jahrbuch Universität Sofia, Agronomische Fakultät 11: 49, 1932.
  2. Atanasoff, Jahrbuch Universität Sofia, Agronomische Fakultät 13: 9, 1934.
  3. Babovic, Sutic, & Bode, Annls Phytopath., numero hors série 203, 1971.
  4. Baumann, Mitt. biol. BundAnst. Ld- u. Forstw. 115: 136, 1965.
  5. Bovey, Annls Phytopath. , numero hors série 225, 1971.
  6. Brandes & Wetter, Virology 8: 99, 1959.
  7. Christoff, Phytopath. Z. 31: 381, 1958.
  8. Cropley, Pl. Path. 17: 66, 1968.
  9. Jordovic, TagBer. dt. Akad. Landw Wiss. Berl. 97: 301, 1968.
  10. Jordovic, Festic & Rankovic, Zast. Bilja 20: 253, 1969.
  11. Kassanis & Sutic, Zast. Bilja 16: 335, 1965.
  12. Kegler, Schmidt & Trifonow, Phytopath. Z. 50: 97, 1964.
  13. Kunze & Krczal, Annls Phytopath., numero hors série 255, 1971.
  14. Németh, Phytopath. Mediterranea 3: 162, 1963.
  15. Németh, Növenytermelés 13: 167, 1964.
  16. Plese, Pilovic & Wrischer, Zast. Bilja 20: 143, 1969.
  17. Rankovic & Jordovic, Zast. Bilja 21: 195, 1970.
  18. Schade, Zentralbl. Bakt. ParasitKde Abt. 2 123: 299, 1969.
  19. Schuch, Z. PflKrankh. PflPath. PflSchutz 69: 137, 1962.
  20. Sutic, Jordovic, Rankovic & Festic, Annls Phytopath., numero hors série 185, 1971.
  21. Trifonow, Zentralbl. Bakt. ParasitKde Abt. 2 123: 340, 1969.
  22. Van Oosten, Neth. J. Pl. Path. 76: 249, 1970.
  23. Van Oosten, Annls Phytopath., numero hors série 195, 1971.
  24. Van Oosten & Bakel, Neth. J. Pl. Path. 76: 313, 1970.


Figure 1

Leaf symptoms in Hauszwetsche plum.

Figure 2

Fruit symptoms (‘plum pox’) in Hauszwetsche plum.

Figure 3

Local lesions in Chenopodium foetidum.

Figure 4

Particles in a purified preparation shadowed with platinum/iridium. Bar represents 500 nm. (Photograph: Dr H. B. Schmidt.)