Details of DPV and References

DPV NO: 286 July 1984

Family: Luteoviridae

Genus: Luteovirus

Species: Bean leafroll virus | Acronym: BLRV

Bean leaf roll virus

J. W. Ashby Plant Diseases Division, DSIR, Private Bag, Christchurch, New Zealand

Contents

Introduction

First described by Quantz & Völk (1954) as ‘Blattrollkrankheit der Ackerbohne und Erbse’ (leaf roll disease of Vicia beans and peas). Virus characterised by Ashby & Huttinga (1979).

Selected synonyms

Pea leaf roll virus (Rev. appl. Mycol. 34: 272)

Pea top yellows virus (Rev. appl. Mycol. 35: 144)

Pea tip yellowing virus (Rev. appl. Mycol. 34: 505)

Legume yellows virus (Rev. appl. Mycol. 59, 1500)

A virus with RNA-containing particles about 27 nm in diameter sedimenting as a single component. Hosts mainly in the Leguminosae. Transmitted by aphids in a persistent manner but not by inoculation of sap. Common in Europe, Middle East, India and USA.

Main Diseases

In broad bean (Vicia faba) the virus causes upward leaf-rolling accompanied by interveinal yellowing of older leaves (Fig. 2) and a decrease in number of pods (Quantz & Völk, 1954). In susceptible varieties of pea (Pisum sativum) it causes general stunting, chlorosis of the youngest leaves and sometimes downward leaf-rolling (Fig. 1, Fig. 4) (Quantz & Völk, 1954). The virus also causes stunting and yellowing of French bean (Phaseolus vulgaris), chickpea (Cicer arietinum), cowpea (Vigna unguiculata) and lentil (Lens esculenta) (Kaiser, 1972; Bos, 1982). Infection in the major perennial hosts, lucerne (alfalfa; (Medicago sativa)) and white clover (Trifolium repens), is usually symptomless. In lucerne, the virus has been associated with a vein-yellowing symptom (Van der Want & Bos, 1959) (Fig. 3) but this symptom is considered by Cockbain & Gibbs (1973) to be caused by another aphid-transmitted agent which requires the presence of BLRV for transmission.

Geographical Distribution

Bean leaf roll virus is common in Europe (Quantz & Völk , 1954; De Fluiter & Hubbeling, 1955 ; Roland, 1955; Cockbain & Gibbs, 1973), the Middle East (Kaiser, 1972), North Africa and India (Bos, 1982). The virus was tentatively identified from lucerne in Michigan (Thottappilly et al., 1977) and has recently been identified from pea crops in Pacific Northwest USA (Hampton, 1983). Diseases reported to have been caused by this virus in New Zealand (Wilson & Close, 1973) are now considered to have been caused by beet western yellows virus (Johnstone et al., 1984).

Host Range and Symptomatology

Not transmissible by mechanical inoculation of sap. Experimentally the virus was transmitted by means of aphids to 25 of 43 species of Leguminosae tested (Cockbain & Gibbs, 1973; Johnstone et al., 1984) and to three of 17 non-legumes tested: Erodium cicutarium, E. moschatum (Geraniaceae) and Montia perfoliata (Portulacaceae) (Johnstone et al., 1984). Thottappilly (1968) transmitted the virus to 65 species of Vicia, Pisum, Medicago, Trifolium, Lathyrus and Trigonella, genera on which the pea aphid occurs naturally. Development of symptoms in most species is greatly enhanced by the use of supplementary lighting and temperatures between 15 and 20°C (Johnstone et al., 1984).

Diagnostic species

Pisum sativum (pea). Symptoms are as described above, but different pea cultivars produce a wide range of responses. The following have proved useful (Drijfhout, 1968; Thottappilly et al., 1977; Johnstone et al., 1984; R. O. Hampton, personal communication).

Sensitive: Onyx (Fig. 4), Laxton’s Superb, Sounder, Charger.
Intermediate: Coquette, Salvo.
Tolerant: Ivy, Sybo, Sparkle.
Immune: Cobri, Lord Chancellor.

Trifolium subterraneum (subterranean clover) cv. Bacchus Marsh and Trifolium incarnatum (crimson clover) cv. Dixie. Mild interveinal yellowing followed by intense reddening, beginning at the margins of older leaves (Fig. 5).

Beta vulgaris (beet) and Capsella bursa-pastoris (shepherd’s purse). Immune to infection (Johnstone et al., 1984).

Propagation species

Pisum sativum cvs Onyx, Eurofin, Charger and Gallaxie are suitable for maintaining cultures and as a source of virus for purification.

Assay species

Small seedlings of Trifolium subterraneum cv. Bacchus Marsh or T. incarnatum cv. Dixie are suitable for assaying transmission by aphid vectors.

Strains

Differences in aphid-transmissibility between two isolates of the virus have been reported (Cockbain & Costa, 1973).

Transmission by Vectors

The principal vector of bean leaf roll virus is the pea aphid, Acyrthosiphon pisum. Myzus persicae is a less efficient vector (Tinsley, 1959; Thottappilly, 1969; Cockbain & Costa, 1973). Macrosiphum euphorbiae is also a vector (Quantz & Völk, 1954). A single transmission by Megoura viciae was recorded by Quantz & Völk (1954) but Cockbain & Costa (1973) found this species to be a non-vector. Aphis fabae is a non-vector of European isolates (De Fluiter & Hubbeling, 1955; Thottappilly, 1969; Cockbain & Costa, 1973) but is reported to transmit the virus in Iran, as are Aphis cracccivora, Aphis gossypii, Acyrthosiphon pisum, Acyrthosiphon sesbaniae and Myzus persicae (Kaiser, 1972).

Transmission of the virus by Acyrthosiphon pisum at 18-24°C requires a minimum acquisition access period of 2 h, a median latent period (Sylvester, 1965) of 105 h and a minimum inoculation access period of 15 min. The virus persists in A. pisum through ecdysis and for up to 16 days, and probably does not multiply in the vector (Cockbain & Costa, 1973). Transmission of American isolates by A. pisum required a 2-4 h acquisition access period and a 2-4 h inoculation access period (R. O. Hampton, personal communication).

Transmission through Seed

The virus was not transmitted in seed from several virus-infected legumes (Kaiser, 1972).

Transmission by Dodder

Not transmitted by dodder (Cuscuta spp.) (Kaiser, 1972).

Serology

The virus is a good immunogen. Rabbit antisera with titres of 1/512 to 1/1024 in Ouchterlony double diffusion tests were obtained (Ashby & Huttinga, 1979). Antisera have also been shown to react with the virus and/or with related luteoviruses in immune density gradients (Ashby & Huttinga, 1979), immunosorbent electron microscopy (ISEM) (Roberts, Tamada & Harrison, 1980) and in enzyme linked immunosorbent assay (ELISA) (Hampton, 1983). Virus was easily detected by ELISA in several hosts including lucerne in which concentrations are very low (R. O. Hampton, personal communication).

Relationships

In gel diffusion tests (Ashby & Huttinga, 1979) bean leaf roll virus was found to react strongly (titre 1/128) with antiserum to soybean dwarf virus (homologous titre 1/1024) and weakly (1/8) with antiserum to beet western yellows virus (homologous titre 1/625 in infectivity neutralisation assay). Reactions with these antisera were also found in immune density gradients (Ashby & Huttinga, 1979). Antiserum to bean leaf roll virus (titre 1/512) reacted with purified subterranean clover red leaf virus, which is closely related to soybean dwarf virus, at a titre of 1/16 in gel diffusion tests (Ashby & Kyriakou, 1983). Antiserum to bean leaf roll virus also reacted weakly with purified potato leafroll virus (Roberts et al., 1980) and with purified carrot red leaf virus (Waterhouse & Murant, 1981). The luteoviruses appear to comprise a continuum of serologically related members.

In comparative host range studies (Johnstone et al., 1984) bean leaf roll virus was shown to be closely similar to a virus isolated from lucerne in Michigan (Thottappilly et al., 1977) and a little less similar to the legume yellows virus reported by Duffus (1979); soybean dwarf virus was not included in these studies. Using ELISA, Hampton (1983) showed legume yellows, the lucerne virus from Michigan and bean leaf roll virus from peas and lucerne in Oregon all to react equally with antiserum prepared to a Dutch isolate of bean leaf roll virus.

Stability in Sap

Acyrthosiphon pisum was unable to transmit the virus after feeding through Parafilm membranes on crude sap from infected plants, presumably because the concentration of virus in such extracts is too low. The aphid could however transmit virus after feeding in the same manner on purified virus preparations. Such preparations still contained transmissible virus after more than 10 days at room temperature (J. W. Ashby, unpublished data).

Purification

(Ashby & Huttinga, 1979). Grow infected pea plants at 15-20°C and harvest 2 wk after inoculation. Homogenise in 4 ml/g of cold 0.1 M phosphate buffer, pH 7.4, containing 0. 1% 2-mercaptoethanol and 10 mM EDTA using a Waring blender. Disintegrate further at higher speed (e.g. in Virtis 45 homogeniser) for 2 min. Centrifuge crude extract at 10,400 g for 10 min and add polyethylene glycol (to 8% w/v) and NaCl (to 3% w/v) to the supernatant fluid. Stir at 4°C for 1 h and centrifuge at 16,300 g for 15 min. Resuspend precipitate in extraction buffer and emulsify with 0.25 vol. of a 1:1 mixture of chloroform and n-butanol. After 1 h, separate phases by centrifugation. Recover virus from the aqueous phase by two cycles of differential centrifugation, resuspending the pellets in 50 mM phosphate buffer, pH 6.5, containing 1 mM EDTA. The virus may be further purified by centrifugation through a 10-40% linear sucrose density gradient (76,000 g, 3.5 h) followed by isopycnic density gradient centrifugation in caesium sulphate. Higher yields of virus (up to 668 µg/kg) were obtained from root tissue than from shoots (Ashby & Huttinga, 1979).

In recent years high yields of many luteoviruses have been obtained by enzyme extraction methods (Takanami & Kubo, 1979). Such methods are in general more efficient than that described above and have proved effective for purification of bean leaf roll virus (R. O. Hampton, personal communication).

Properties of Particles

In sucrose density gradients the particles sediment as a single component (Ashby & Huttinga, 1979).

Buoyant density in Cs₂SO₄: 1 .32 g/cm³.

A₂₆₀/A₂₈₀ : 1 .83 (not corrected for light-scattering).

Particle Structure

Particles are isometric, about 27 nm diameter, in preparations negatively stained with uranyl acetate (Fig. 6) (Ashby & Huttinga, 1979).

Particle Composition

Nucleic acid: Single-stranded RNA with estimated M. Wt c. 2.4 x 10⁶ under non-denaturing conditions.

Protein: In SDS/polyacrylamide gel electrophoresis, a single polypeptide was detected, with estimated M. Wt 32,500 (Ashby & Huttinga, 1979). This seems unusually high and the value of 23,000 obtained by R. O. Hampton (personal communication) is more typical for a luteovirus.

Relations with Cells and Tissues

Virus-like particles were observed in necrotic phloem sieve-tube cells of virus-infected broad bean and crimson clover. The particles were scattered singly or in masses throughout the lumen of infected cells and were interspersed with remnants of cell organelles (Thottappilly et al., 1977).

Notes

Confusion over the proper name for bean leaf roll virus and the disease caused by it were discussed by Bos (1964) who suggested that preference be given to the name pea leaf roll virus. The first description of the disease ‘Blattrollkrankheit der Ackerbohne’ was by Böning (1927) and the viral nature of the disease in Vicia-beans and peas was demonstrated by Quantz & Völk (1954). The name leaf roll is descriptive of the symptoms caused in beans whereas in peas the main symptom is apical yellowing. Thus on the basis of priority and descriptiveness bean leaf roll is the most appropriate name for the virus.

Several luteoviruses of legumes resemble bean leaf roll virus and apparent differences between some of them were described by Tamada & Kojima (1977). There is increasing evidence that one of those described, subterranean clover stunt virus, may not be a member of the luteovirus group (G. R. Johnstone, personal communication). A tentative proposal for grouping the luteoviruses that resemble bean leaf roll virus is given in Table 1. A list of key hosts and of procedures for studying host range and vector specificity is given by Johnstone et al. (1984). Although imprecise, these methods permit workers who do not have access to such techniques as ISEM and ELISA to make a tentative identification of luteoviruses isolated from leguminous hosts. Among such viruses, beet western yellows virus is the one most likely to be confused with bean leaf roll virus; however, although beet western yellows virus has a wide host range in the Leguminosae, it also infects non-legumes such as Capsella bursa-pastoris, Beta vulgaris and Lactuca sativa, all of which are immune to bean leaf roll virus. Also, unlike bean leaf roll virus, it is efficiently transmitted by Myzus persicae and several other aphid species. The unusually large number of aphid species (seven) able to transmit bean leaf roll virus isolates in Iran (Kaiser, 1972) suggests a possible involvement of a beet western yellows-like virus in the aetiology of the disease in that country.

Mixed infections of luteoviruses may occur in the same plant and it is advisable to do transmission tests with a number of aphid species normally associated with the plant and a selected group of indicators as suggested by Johnstone et al. (1984).

With the application of ELISA (Hampton, 1983) and ISEM (Roberts et al., 1980) it has become possible to quantify relationships between members of the luteovirus group; bean leaf roll virus can readily be distinguished from beet western yellows virus by ELISA (R. O. Hampton, personal communication). Serological tests and vector specificity however reflect only the nature of the particle protein. In mixed luteovirus infections in plants there may be an interchange of protein coats (heterologous encapsidation) with concomitant changes in serological reaction and vector specificity (Rochow, 1977).

Bean leaf roll virus is commonly recorded from Vicia-bean crops in the United Kingdom and Europe but rarely causes significant economic losses. Many of the pea cultivars grown in these areas are resistant to the virus, and losses occur only where susceptible vining peas are grown near lucerne crops. In the USA, bean leaf roll virus had never been reported on peas prior to 1980, when it caused a major epidemic in Southern Idaho where more than 80% of the US pea seed crop is produced annually (Hampton, 1983).

Control of bean leaf roll virus in peas is best achieved by use of resistant cultivars; in Vicia beans, in which no sources of immunity have been demonstrated, control is by avoiding proximity to lucerne crops.

Table 1. Bean leaf roll and similar luteoviruses of legumes and their vectors

Preferred name (accepted synonyms)	No. of aphid vector species recorded		Main aphid vector(s)		Viruses closely related serologically*
BEAN LEAF ROLL (pea leaf roll) (pea top (tip) yellows)	7		Acyrthosiphon pisum Aulacorthum solani		legume yellows, Michigan lucerne
SOYBEAN DWARF	4		Aulacorthum solani		subterranean clover red leaf
MILK VETCH DWARF	3		Aphis craccivora
INDONESIAN SOYBEAN DWARF	1		Aphis glycines
BEET WESTERN YELLOWS (beet mild yellowing) (malva yellows) (turnip yellows)	10		<Myzus persicae

*Groundnut rosette assistor virus has relationships with bean leaf roll virus and beet western yellows virus but the closeness of these relationships is not yet clear (Casper et al., 1983; D.V.R. Reddy, A.F. Murant and G.H. Duncan, unpublished data).

Figures

References list for DPV: Bean leaf roll virus (286)

1. Ashby & Huttinga, Neth. J. Pl. Path. 85: 113, 1979.
2. Ashby & Kyriakou, N.Z. Jl agric. Res. 25: 607, 1983.
3. Böning, Forschn Geb. PflKrankh., Berl. 4: 43, 1927.
4. Bos, Neth. J. Pl. Path. 70: 161, 1964.
5. Bos, in Faba Bean Improvement, p. 233, ed. G. Hawtin & C. Webb, The Hague, Martinus Nijhoff, 390 pp., 1982.
6. Casper, Meyer, Lesemann, Reddy, Rajeshwari, Misari & Subbarayudu, Phytopath. Z. 108: 12, 1983.
7. Cockbain & Costa, Ann. appl. Biol. 73: 167, 1973.
8. Cockbain & Gibbs, Ann. appl. Biol. 73: 177, 1973.
9. De Fluiter & Hubbeling, Tidschr. PlZiekt. 61: 165, 1955.
10. Drijfhout, Euphytica 17: 224, 1968.
11. Duffus, Phytopathology 69: 217, 1979.
12. Hampton, Pl. Dis. 67: 1306, 1983.
13. Johnstone, Ashby, Gibbs, Duffus, Thottappilly & Fletcher, Neth. J. Pl. Path. 90: 225, 1984.
14. Kaiser, Pl. Prot. Bull. F.A.O. 20: 127, 1972.
15. Quantz & Völk, NachrBl. dt. PflSchutzdienst., Stuttg. 6: 177, 1954.
16. Roberts, Tamada & Harrison, J. gen. Virol. 47: 209, 1980.
17. Rochow, in Aphids as Virus Vectors, p. 253, eds K. Harris & K. Maramorosch, New York: Academic Press, 559 pp., 1977.
18. Roland, Parasitica 11: 66, 1955.
19. Sylvester, Virology 25: 62, 1965.
20. Takanami & Kubo, J. gen. Virol. 44: 153, 1979.
21. Tamada & Kojima, CMI/AAB Descr. Pl. Viruses 179, 4 pp., 1977.
22. Thottappilly, Z. PflKrankh. PflPath. PflSchutz. 76: 67, 1968.
23. Thottappilly, Phytopath. Z. 64: 327, 1969.
24. Thottappilly, Kao, Hooper & Bath, Phytopathology 67: 1451, 1977.
25. Tinsley, Pl. Path. 8: 17, 1959.
26. Van der Want & Bos, Tijdschr. PlZiekt. 65: 73, 1959.
27. Waterhouse & Murant, Ann. appl. Biol. 97: 191, 1981.
28. Wilson & Close, N.Z. Jl agric. Res. 16: 305, 1973.