280
July 1984
Family: Bromoviridae
Genus: Ilarvirus
Species: American plum line pattern virus
Acronym: APLPV


American plum line pattern virus

R. W. Fulton
Department of Plant Pathology, University of Wisconsin, Madison, WI 53706, USA

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

The disease was described by Valleau (1932), Cation (1941) and Zeller & Milbrath (1942). The virus was transmitted by sap and its properties described by Kirkpatrick, Cheney & Lindner (1964) and Paulsen & Fulton (1968).

Synonyms

Plum line pattern virus (in part) (Rev. appl. Mycol. 44: 177)
Peach line pattern virosis virus (Rev. appl. Mycol. 25: 218)
Marmor pallidolimbatus, Prunus virus 10 (Rev. appl. Mycol. 21: 532)

A virus with RNA-containing particles about 26, 28, 31 and 33 nm in diameter, sedimenting as four components. The virus is transmitted by inoculation of sap, more readily from experimental herbaceous hosts than from its natural woody hosts. The virus loses infectivity rapidly in sap unless an antioxidant is present. No vector known. Reported from USA and Canada.

Main Diseases

The virus causes ‘line pattern’ diseases (chlorotic lines and bands) in Prunus domestica and other plums, oriental flowering cherry (P. serrulata), peach (P. persica; Fig.2) and other Prunus spp. (Kirkpatrick & Fulton, 1976). However, very similar symptoms are induced by apple mosaic virus and certain strains of prunus necrotic ringspot virus, neither of which is serologically related to American plum line pattern virus.

Geographical Distribution

Reported from the USA and Canada (Willison, 1945). It may, however, be more widely distributed because line pattern diseases have been reported from most countries where plums are grown, but the identity of the viruses present is not known for many of the earlier reports.

Host Range and Symptomatology

The virus has a wide host range; it infected 85 of 245 species inoculated with sap, including six woody rosaceous species (Paulsen & Fulton, 1968). It occurs naturally in many varieties of plum and other Prunus spp. (Kirkpatrick & Fulton, 1976).

Diagnostic species

Cucumis sativus (cucumber). May develop small (2 nm) chlorotic lesions in inoculated cotyledons, but the virus does not become systemic.

Nicotiana megalosiphon. Inoculated leaves develop chlorotic or diffusely necrotic primary lesions. Systemic symptoms consist of a mild ringspotting or mottle (Fig.3).

Physalis floridana. Inconspicuous chlorotic primary lesions followed by systemic chlorotic veinbanding, ringspotting or oak-leaf patterns.

Prunus spp. Chlorotic lines, rings and oak-leaf patterns of varying severity (Fig.2). In myrobalan and Shiro plum (P. cerasifera and P. americana x P. salicina) , some leaves may show ‘yellow net’ symptoms bordering the veins and veinlets. Ember plum reacts more severely than Shiro plum, which is commonly used as an indicator host (Fridlund, 1958).

Vigna unguiculata ssp. cylindrica (catjang). Small reddish lesions within 3-4 days in primary leaves, provided that they are inoculated when about two-thirds expanded (Fig.1). Systemic symptoms consist of a characteristic reddish etching of the veins of trifoliolate leaves, with stunting and curling (Fig.4).

Propagation species

Cultures may be maintained in Prunus spp. or in Vinca rosea. Young leaves of V. rosea, or petals of Prunus, provide the most infective inoculum. The virus may be propagated for purification in Nicotiana megalosiphon or N. occidentalis.

Assay species

Vigna unguiculata spp. cylindrica has been used as a local lesion host. Many other leguminous species develop necrotic local lesions but in most species the lesions are few.

Strains

The isolate described by Kirkpatrick et al. (1964) infected a number of species (Gomphrena globosa, Lactuca sativa, Nicotiana glutinosa, N. rustica, Tithonia speciosa) that were apparently not susceptible to a Wisconsin isolate.

Transmission by Vectors

No vectors described.

Transmission through Seed

Seed transmission in Prunus has not been investigated. The virus was not transmitted through seed of Petunia hybrida, P. violacea or Phaseolus vulgaris (A. Q. Paulsen & R. W. Fulton, unpublished data).

Transmission by Dodder

Cuscuta campestris transmitted the virus from Nicotiana megalosiphon to Petunia hybrida, but C. subinclusa did not.

Serology

The virus is a moderately good immunogen in rabbits. Intramuscular injections twice a week of 1.8-2.0 mg of purified virus in Freund’s incomplete adjuvant resulted in antiserum titres of 1/1280-1/2560 after 6-7 weeks. Agar gel double diffusion tests showed a single line of precipitate with extracts of herbaceous hosts, but only ELISA was effective for detecting the virus in woody hosts (Fulton, 1982).

Relationships

The isolate of American plum line pattern virus described by Kirkpatrick et al. (1964) reacted strongly with antiserum to a Wisconsin isolate although their host ranges were not identical (Paulsen & Fulton, 1968). The properties and morphology of the virus suggest affinities with the ilarviruses (Fulton, 1983), but Paulsen & Fulton (1969) detected no serological relationship to three members of that group, prune dwarf, prunus necrotic ringspot and apple mosaic viruses, the last two of which also cause line pattern symptoms in plum. Barnett & Murant (1970) found no reaction between antiserum to American plum line pattern virus and raspberry bushy dwarf virus.

Stability in Sap

Undiluted sap of infected N. megalosiphon was not infective even when inoculated to catjang test plants immediately after preparation, but extracts made by grinding tissue in several volumes of phosphate buffer had some infectivity. Infectivity was stabilised for 4 h or more by grinding N. megalosiphon tissue in buffer containing 0.02 M 2-mercaptoethanol. In such extracts, assayed on catjang, the thermal inactivation point (10 min) of the virus was 66°C, and the dilution end-point was between 1/6400 and 1/12,800 (Paulsen & Fulton, 1968). The virus retained infectivity for several years when infected tissue of Petunia hybrida was dried over CaCl2 at 2°C.

Purification

(Paulsen & Fulton, 1969). Mature leaves of N. megalosiphon or N. occidentalis heavily inoculated 6-10 days previously with extracts from the same host, or from systemically infected leaves of catjang, are a suitable source of virus for purification. Homogenise the leaves in cold 0.02 M phosphate buffer, pH 8.0, containing 0.02 M 2-mercaptoethanol, at the rate of 1.5 ml/g tissue. Centrifuge the homogenate at low speed (1800 g for 0. 5 h) and adjust the supernatant liquid to pH 4.8 with 0.1 M citric acid. After holding at 4°C for 2 h, remove the green precipitate by centrifuging the extract at 1800 g for 20 min. Then adjust the supernatant liquid to pH 6.5-7.0 and centrifuge again at 1800 g for 0.5 h. Concentrate the virus from the clarified extract by centrifuging at 78,000 g for 3 h. Resuspend the pellets in 0.02 M EDTA, pH 6.2, and remove any insoluble material by low speed centrifugation. Repeat the high and low speed centrifugation cycle. The gamma globulin portion of antiserum to healthy N. megalosiphon has been used to remove remaining host protein (Paulsen & Fulton, 1969). This may also be done by centrifuging the preparation in sucrose gradients (7-25%) prepared in 0.03 M EDTA (Fulton, 1982). Yields of virus are about 2 mg/100 g fresh leaves. The particles disrupt quickly in water or a number of buffers, but retain morphological integrity and infectivity for several years in 0.03 M EDTA, pH 6.2, at 4°C. Purified virus retained infectivity longer in ammonium phosphate (pH 8.0) than in sodium or potassium phosphate.

Properties of Particles

Preparations of virus particles sediment as four components (T, M, B1 and B2) in sucrose density gradients (Fig.5). The separated components were only weakly infective, mixtures of all four components were the most infective; however the components were probably not completely separated.

Sedimentation coefficients (s20, w): about 95, 100, 114 and 125 S in comparison with known viruses as standards (Fulton, 1982).

A260/A280: 1.67 (unfractionated virus).

Particle Structure

The nucleoprotein particles are quasi-isometric (Fig.6) and those from the four bands in sucrose density gradients have diameters of 26, 28, 31 and 33 nm, from the uppermost to the lowest band.

Particle Composition

Nucleic acid: No information. However, by analogy with similar multicomponent viruses the nucleic acid is probably single-stranded RNA. If so the A260/A280 ratio would suggest that the RNA comprises about 16% of the particle weight.

Protein: No information.

Relations with Cells and Tissues

No information.

Notes

American plum line pattern virus is not serologically related to either prunus necrotic ringspot or apple mosaic viruses and does not cause mosaic in apple. All three of these (or strains of them) may cause line pattern in plum. The specific designation ‘American plum line pattern virus’ was suggested by Seneviratne & Posnette (1979). Other terms e.g. apricot line pattern (Schuch, 1961), are presumed to refer to apple mosaic or prunus necrotic ringspot viruses.

References

  1. Barnett & Murant, Ann. appl. Biol. 65: 435, 1970.
  2. Cation, Phytopathology 31: 1004, 1941.
  3. Fridlund, Pl. Dis. Reptr 42: 1051, 1958.
  4. Fulton, Phytopathology 72: 1345, 1982.
  5. Fulton, CMI/AAB Descr. Pl. Viruses, 275, 3 pp., 1983.
  6. Kirkpatrick, Cheney & Lindner, Pl. Dis. Reptr 48: 616, 1964.
  7. Kirkpatrick & Fulton, in Virus Diseases and Noninfectious Disorders of Stone Fruits in North America. U.S. Dept. Agric., Agric. Handbook 437, 166, 1976.
  8. Paulsen & Fulton, Phytopathology 58: 766, 1968.
  9. Paulsen & Fulton, Ann. appl. Biol. 63: 233, 1969.
  10. Schuch, Z. PflKrankh. 68: 10, 1961.
  11. Seneviratne & Posnette, Ann. appl. Biol. 65: 115, 1970.
  12. Valleau, Res. Bull. Ky agric. Exp. Stn 327: 89, 1932.
  13. Willison, Phytopathology 35: 991, 1945.
  14. Zeller & Milbrath, Phytopathology 32: 634, 1942.


Figure 1

Primary lesions in Vigna unguiculata ssp. cylindrica (catjang) 4 days after inoculation.

Figure 2

Systemic symptoms in peach.

Figure 3

Systemically infected leaf of Nicotiana megalosiphon.

Figure 4

Systemic symptoms in first trifoliolate leaf of V. unguiculata spp. cylindrica.

Figure 5

Distribution of sedimenting components T, M, B1 and B2 after centrifugation in a density gradient of sucrose (7-25%) for 4 h at 25,000 rev/min in a Beckman SW 25.1 rotor.

Figure 6

Purified virus particles, fixed with glutaraldehyde and negatively stained with sodium phosphotungstate. Bar represents 100 nm.