Beet western yellows virus
J. E. Duffus
US Agricultural Research Station, Salinas, California 93901, USA
Contents
Introduction
Described by Duffus (
1960,
1961).
- Selected synonyms
- Turnip yellows virus (Rev. appl. Mycol. 32: 294)
- Malva yellows virus (Rev. appl. Mycol. 39: 761)
- Radish yellows virus (Rev. appl. Mycol. 39: 753)
- Turnip mild yellows virus (Rev. appl. Mycol. 42:
651)
A virus with isometric particles c. 26 nm in diameter.
Transmitted by several species of aphids in the persistent
(circulative) manner, but not by sap inoculation. It has a wide
host range among commercially important crop plants. Distribution
probably world-wide.
Main Diseases
Causes stunting and chlorosis of a wide range of
dicotyledonous species, including sugar beet, red beet, spinach,
lettuce, broccoli, cauliflower, radish, turnip and flax.
Geographical Distribution
Reported from North America, Europe (
Duffus & Russell, 1970)
and Asia (
Sugimoto, Murayama & Sanai, 1970); probably common
throughout the world.
Host Range and Symptomatology
Host range is wide; over 100 species in 21 dicotyledonous
families are susceptible to various strains of the virus
(
Duffus, 1960). Occurs naturally in a number of common weed
species and often in common overwintering hosts of vector aphids
(
Wallis, 1967). Transmitted readily by aphids but not by sap
inoculation. Interveinal yellowing of the older or intermediate
leaves, especially under high light intensity, is the most
common symptom (
Fig.1).
- Diagnostic species
- Capsella bursa-pastoris. Severe chlorosis and
moderate leaf curl, thick and brittle leaves (Fig.2);
yellowing develops acropetally. On some biotypes of
Capsella, purpling or reddening accompanies the chlorosis.
- Senecio vulgaris. Purple coloration of the margins
of mature leaves.
- Claytonia perfoliata. Pink to salmon coloration of
the edges of older leaves.
- Propagation species
- Beta vulgaris (sugar beet), Raphanus sativus
(radish) and Capsella bursa-pastoris are suitable for
maintaining cultures; and the two last species as sources of
virus for purification.
- Assay species
- Capsella bursa-pastoris, by determining the
proportion of seedlings that become infected. The plants
should be inoculated by means of single aphids given 24 hr
acquisition feeds on infected plants or plant extracts.
Strains
Many variants have been distinguished on the basis of
host range and virulence (
Duffus, 1964). Different variants
seem to predominate in different plant species,
e.g.
malva yellows virus (
Costa, Duffus & Bardin, 1959) in
Malva, turnip yellows virus (
Vanderwalle & Roland,
1951) in turnip. Different variants may induce similar reactions
in some plant species but distinct reactions in others in regard
to susceptibility, stunting and yellowing. All isolates so far
tested infect
Capsella bursa-pastoris, Claytonia
perfoliata and
Senecio vulgaris. The variants do not
cross-protect (
Duffus & Gold, 1969).
Transmission by Vectors
Transmissible by 8 species of aphids, the most important
of which is
Myzus persicae. Transmission is in the
persistent (circulative) manner; the virus persists in the
vector for over 50 days. Vectors retain ability to transmit
after moulting, but the virus is not transmitted to their
progeny. Minimum acquisition feeding period, 5 min; minimum
inoculation feeding period, 10 min. There is a latent period
of 12-24 hr. Some differences between virus isolates in their
efficiency of transmission by vectors are related to differences
in virus concentration in the plant hosts (J. E. Duffus,
unpublished).
Transmission through Seed
Not known to occur.
Transmission by Dodder
Not known to occur.
Serology
The virus is strongly immunogenic but occurs in low
concentrations in plants and partially purified preparations
must be used in serological tests. Serological neutralization
of infectivity, demonstrated by feeding insects through
membranes on virus-antiserum mixtures, has been successful
with virus or antiserum concentrations too low for conventional
serological techniques (
Duffus & Gold, 1965,
1969;
Gold & Duffus, 1967).
Relationships
A number of viruses transmitted in the persistent manner
by
Myzus persicae have certain host plants and host
reactions in common (beet western yellows, beet mild yellowing,
malva yellows,
potato leaf roll, turnip latent and turnip
yellows viruses). Using antiserum to beet western yellows
virus in infectivity neutralization tests, malva yellows and
turnip yellows viruses have been shown to be closely related
to beet western yellows virus; however, potato leaf roll virus
appears not to be serologically related (
Duffus & Gold,
1969; J. E. Duffus & G. E. Russell, unpublished). Beet
mild yellowing virus (
Russell, 1958), produces similar symptoms
in certain key indicator hosts and is transmitted in a similar
way by vectors but differs greatly in epidemiology and host range
from typical isolates of beet western yellows virus (
Russell, 1963,
1965;
Björling & Nilsson, 1966). No tests of the
serological relationship between beet mild yellowing and beet
western yellows viruses have been made and it would seem best
at present to regard these viruses as separate.
Stability in Sap
Determined for several isolates by feeding aphids through
membranes on partially purified virus preparations. Thermal
inactivation point (10 min) is about 65°C; dilution end-point
of unconcentrated sap 1/8; extracts were infectious after 16
days at 24°C. Alternate freezing and thawing at 4 or 5
day intervals for 1 month had no effect on virus activity.
Infectivity withstood drying for at least 3 years (
Duffus,
1969).
Purification
Several strains have been purified by chloroform clarification,
differential centrifugation, density gradient centrifugation and
density gradient electrophoresis (
Smith, Duffus & Gold, 1966;
Gold & Duffus, 1967).
Properties of Particles
Not known.
Particle Structure
Particles are isometric; diameter about 26 nm in thin sections
of host tissue (
Fig.3)
Esau & Hoefert, 1972a;
Ruppel,
1968).
Particle Composition
Not known.
Relations with Cells and Tissues
Particles appear to be confined to the phloem and associated
with phloem degeneration. They may occur in nuclei of phloem
parenchyma cells (
Esau & Hoefert, 1972b).
Notes
Leaves of infected beet plants are more susceptible to attack
by
Alternaria species than are healthy plants or plants
infected with beet yellows virus (J. E. Duffus, unpublished).
References
- Björling & Nilsson, Socker 21: 1, 1966.
- Costa, Duffus & Bardin, J. Am. Soc. Sug. Beet Technol. 10: 371, 1959.
- Duffus, Phytopathology 50: 389, 1960.
- Duffus, Phytopathology 51: 605, 1961.
- Duffus, Phytopathology 54: 736, 1964.
- Duffus, Phytopathology 59: 1668, 1969.
- Duffus & Gold, Virology 27: 388, 1965.
- Duffus & Gold, Virology 37: 150, 1969.
- Duffus & Russell, Phytopathology 60: 1199, 1970.
- Esau & Hoefert, J. Ultrastruct. Res. 40: 556, 1972a.
- Esau & Hoefert, Virology 48: 724, 1972b.
- Gold & Duffus, Virology 31: 308, 1967.
- Ruppel, Phytopathology 58: 256, 1968.
- Russell, Ann. appl. Biol. 46: 393, 1958.
- Russell, Ann. appl. Biol. 52: 405, 1963.
- Russell, Ann. appl. Biol. 55: 245, 1965.
- Smith, Duffus & Gold, Phytopathology 56: 902, 1966.
- Sugimoto, Murayama & Sanai, Bull. Sugar Beet Res. 8: 1, 1970.
- Vanderwalle & Roland, Parasitica 7: 14, 1951.
- Wallis, J. econ. Ent. 60: 904, 1967.
Systemic symptoms in leaves of greenhouse plants
(a) Zinnia elegans,
(b) Beta vulgaris,
(c) Verbesina encelioides,
(d) Nicandra physalodes,
(e) Lactuca sativa,
(f) Nicotiana clevelandii.
Leaves of Capsella bursa-pastoris:
(below) healthy (above) infected with beet western yellows virus.
Thin section of degenerating parenchyma cells of
Capsella bursa-pastoris showing virus particles and remains
of cytoplasm. Bar represents 100 nm.
