Cauliflower mosaic virus
R. J. Shepherd
Department of Plant Pathology, University of California, Davis, California, USA
- Brassica virus 3 (Rev. appl. Mycol. 36: 303)
- Broccoli mosaic virus (Rev. appl. Mycol. 22: 122)
- Cabbage mosaic virus (Rev. appl. Mycol. 19: 65)
- Cabbage virus B (Rev. appl. Mycol. 24: 438)
A DNA-containing virus with isometric particles about 50 nm in diameter. It is
transmitted by several aphid species in a non-persistent or semi-persistent manner
and is readily transmissible by mechanical means. It is found only in
cruciferous plants in which it is widely distributed in temperate regions.
Induces mosaic and mottle diseases in a wide range of
cruciferous crop and ornamental species, particularly the various cultivars of
and B. oleracea.
Often found in mixed
turnip mosaic virus
World wide, especially in temperate regions.
Host Range and Symptomatology
With the exception of Nicotiana
(Hills & Campbell, 1968
only members of the Cruciferae
have been reported as hosts. The virus is readily transmissible mechanically
using an abrasive.
- Brassica oleracea var. botrytis (cauliflower): Inoculated leaves
usually symptomless; systemically infected leaves show initial vein-clearing,
gradually replaced by green vein-banding
Some varieties show only
faint persistent vein-clearing, which may become masked in chronically infected
plants, particularly at high temperatures.
- B. campestris (Tendergreen mustard; also known as B. perviridis).
Some inoculated leaves develop chlorotic local lesions
are vein-clearing, followed by chlorotic mottle
- Matthiola incana var. annua (annual stock). Systemic chlorotic
Propagation and assay species
- Tendergreen mustard (B. campestris).
Minor variants can be distinguished by their virulence in
cauliflower or turnip
(Broadbent & Tinsley, 1953
Most isolates consist
of a mixture of strains, of which some become systemic in Tendergreen mustard
without inducing local lesions, and others induce local chlorotic lesions but
do not become systemic.
Transmission by Vectors
At least 27 aphid spp. have been reported to
transmit the virus
(Kennedy, Day & Eastop, 1962
in a non-persistent or
semi-persistent manner. All instars transmit and there is no latent period.
Aphids can acquire the virus in 1-2 min and immediately thereafter can inoculate
plants in less than 1 min. The virus is retained by Myzus persicae
more than 3 h, i.e.,
considerably longer than the typical non-persistent
type viruses. Retention is unaffected by post-acquisition feeding activity
Transmission through Seed
The virus is moderately immunogenic in rabbits. Purified virus
gives a single band of precipitate in gel-diffusion tests in 1% agar but the
virus is usually present in infected plants in insufficient amounts, or is
liberated from inclusion bodies too slowly, to give reactions in agar
gel-diffusion tests or tube precipitin tests with clarified leaf extracts
(Pirone, Pound & Shepherd, 1961
In the presence of sufficient salt
(0.2 M acetate) the virus adsorbs to polystyrene latex particles and these
provide an extremely sensitive indicator system for serology.
The virus is serologically closely related to dahlia
Stability in Sap
In cauliflower sap, the thermal inactivation point is
75-80°C (10 min), dilution
, and longevity at 20°C 5-7 days.
The concentration of virus in infected plants is usually
less than 5 mg/kg of plant tissue. The following method is useful
(Pirone, Pound & Shepherd, 1960
Homogenize tissue in 0.5 M phosphate (pH 7.5),
-butanol to 8.5% (v/v) and centrifuge at 8000 g
Retain supernatant fluid and concentrate virus by 2-3 cycles of differential
centrifugation using water as the solvent. Finally purify by sucrose density-gradient
centrifugation. For large quantities of infected tissue (10-20 kg), precipitate
the virus from butanol-clarified extracts by adding sodium chloride (to 0.05 M)
and polyethylene glycol, 6000 M. Wt (100 g/l of extract); resuspend the
precipitated virus in water and concentrate by 2 cycles of differential
(Shepherd, Bruening & Wakeman, 1970
The virus can be freed
of host material by incubation with pancreatic ribonuclease (40 µg/ml)
and centrifugation to equilibrium in CsCl gradients
(Shepherd, Wakeman & Romanko, 1968
Properties of Particles
Sedimentation coefficient (s20,w
): 220 S
(Pirone et al., 1961
Buoyant density in CsCl: 1.37 g/ml.
Uncorrected absorbance at 260 nm (1 mg/ml, 1 cm light path): 7.
Specific refractive increment: 1.8 x 10-4/mg/ml.
The particle is roughly spherical with a diameter
50 nm. It flattens considerably when preparations are air-dried on
electron microscope grids. This can be prevented by freeze-drying
(Pirone et al., 1961
The particles are penetrated by potassium phosphotungstate and
appear empty, with a diameter of 50 nm and a hollow centre of 20 nm diameter.
In uranyl acetate the particles
appear 45 nm in diameter and the stain
does not penetrate
(Hills & Campbell, 1968
Double stranded, about 16% of particle weight, molecular weight
4.5 x 106
buoyant density in CsCl: 1.702 g/ml. Melts at 87.2°C and has 43% G+C
(Shepherd et al., 1970
Protein: No information.
Relations with Cells and Tissues
Virus particles are found only in
the cytoplasm of infected cells, usually in association with a granular,
electron-dense material that forms the bulk of the prominent inclusion
bodies present in chronically infected plants. These inclusion bodies, when
fully developed, consist of compact, elliptical masses of material with vacuoles,
but without membranes. Virus particles are randomly scattered throughout the
granular matrix and most are near the periphery and within the vacuoles
In epidermal strips stained for 1 min with 0.5% phloxine, followed by thorough
removal of excess stain with water, the deeply stained (reddish-pink) roughly
spherical inclusion bodies are visible in the cytoplasm of virtually every cell
(Fujisawa et al., 1967
This is useful in diagnosis of the virus.
Cauliflower mosaic virus may be differentiated from other
non-persistent, aphid-borne viruses found in crucifers (e.g.,
turnip mosaic virus
by its relatively high thermal inactivation point (75-80°C), its
longevity in vitro
(5-7 days) and restricted host range
(Walker, LeBeau & Pound, 1945
Unlike turnip mosaic virus, it does not infect solanaceous
or chenopodiaceous plants, with the exception of Nicotiana clevelandii.
The characteristic inclusion bodies it induces in chronically infected plants
provide a convenient means of diagnosis.
- Broadbent & Tinsley, Pl. Path. 2: 88, 1953.
- Brunt, Virology 28: 778, 1966.
- Kennedy, Day & Eastop, A conspectus of aphids as vectors of plant viruses, London, Commonwealth Institute of Entomology, 1962.
- Fujisawa, Rubio-Huertos, Matsui & Yamaguchi, Phytopathology 57: 1130, 1967.
- Hamlyn, Pl. Path. 4: 13, 1955.
- Hills & Campbell, J. Ultrastruct. Res. 24: 134, 1968.
- Pirone, Pound & Shepherd, Nature, Lond., 186: 656, 1960.
- Pirone, Pound & Shepherd, Phytopathology 51: 541, 1961.
- Shepherd, Wakeman & Romanko, Virology 36: 150, 1968.
- Shepherd, Bruening & Wakeman, Virology 41: 339, 1970.
- Tompkins, J. agric. Res. 55: 33, 1937.
- Walker, LeBeau & Pound, J. agric. Res. 70: 379, 1945.
Systemically infected leaf of Brassica oleracea var.
Chlorotic local lesions in inoculated leaf of B. campestris
Inclusion body in epidermal cell of B. campestris (Tendergreen
mustard), showing virus particles embedded in the densely-staining granular
matrix. Bar represents 500 nm. (Photo courtesy A. Allison).
Systemically infected leaf of B. campestris.
Epidermal strip from infected B. campestris showing the
characteristic inclusion bodies after staining with phloxine.
Purified virus in uranyl acetate. Bar represents 100 nm. (Photo
courtesy Scottish Horticultural Research Institute.)