Nicotiana velutina mosaic virus
J. W. Randles
Department of Plant Pathology, Waite Agricultural Research Institute, The University of Adelaide, Glen Osmond, South Australia, 5064
Randles, Harrison & Roberts (1976)
An RNA-containing virus with straight rod-shaped particles 18 nm in diameter,
and a large range of lengths, the commonest being 125-150 nm. Transmissible
through seed, and by mechanical inoculation of sap to plants in three families.
Has no known economic importance.
Isolated from a Nicotiana velutina
plant showing bright yellow mosaic.
Only known occurrence is adjacent to a dam 8 km from Lake Frome Station
Homestead, in the semi-arid region of South Australia.
Host Range and Symptomatology
Fairly readily transmissible by inoculation of sap. Infects species in the
Solanaceae (including many Nicotiana
species) and Chenopodiaceae;
(Amaranthaceae) is the only known host outside these
families. Symptom intensity and speed of development vary with light and
temperature conditions, and are favoured by continuous light of approximately
5000 lux at 25°C.
Nicotiana glutinosa. Inoculated leaves are usually symptomless but may
develop chlorotic rings. Systemic vein chlorosis and mosaic persist throughout
the life of the plant
Nicotiana tabacum (tobacco) cv. Xanthi-nc. Inoculated leaves develop
delicate necrotic rings and lines. A systemic mild mosaic is produced.
Nicotiana debneyi. Large spreading chlorotic blotches develop in
inoculated leaves, sometimes accompanied by delicate necrotic rings. The first
leaf with systemic symptoms becomes yellow, often with necrosis. Leaves produced
later show a mild mosaic, rugosity, and narrowing of the lamina
Chenopodium amaranticolor and C. quinoa. Chlorotic local lesions,
becoming necrotic. Not infected systemically
Beta macrocarpa. Chlorotic local lesions and systemic mosaic
Gomphrena globosa. Enlarging local necrotic ringspots. Systemic chlorosis
with crinkling and epinasty of leaves
Tetragonia expansa is not a host.
Nicotiana glutinosa plants and seed are suitable for maintaining inoculum;
N. debneyi is favoured as a source for virus purification.
Chenopodium amaranticolor and C. quinoa are useful local lesion hosts.
Transmission by Vectors
Transmission through Seed
Frequently transmitted through the seed of Nicotiana glutinosa
72%), N. clevelandii, N. debneyi
and N. rustica
The virus is moderately to poorly immunogenic. Tube precipitin tests, and
double diffusion in gels containing agarose at 0.5% and below are satisfactory.
Observation of antigen-antibody agglutination by electron microscopy is favoured
for studying cross-reactions because specific attachment of antibody to antigen
can be observed, sensitivity is high, and requirements for reactants are small.
Host range and structure of the virus suggest relatedness to the rod-shaped
fungus-transmitted viruses such as
potato mop-top virus
which are now regarded
as tentative members of the
However, the size of the coat
protein subunits, and the frequent seed transmission suggest that it may also
be allied to
barley stripe mosaic virus
No serological relationship has been found between Nicotiana velutina
mosaic virus and potato mop-top,
soil-borne wheat mosaic,
beet necrotic yellow vein,
barley stripe mosaic or
tobacco rattle viruses.
Stability in Sap
Sap of infected N. glutinosa
or N. debneyi
when stored from 1 to 4 days at room temperature. Infectivity declines in sap
heated at 50°C for 10 min, and is lost after 10 min at between 60° and
70°. The dilution end-point of infective N. glutinosa
sap, diluted in
water and tested on N. glutinosa,
is between 10-1
Infectivity is enhanced and greatly stabilized by adding reducing agents (for
example 0.002 M dithiothreitol or 0.05% thioglycerol), but not chelating agents
(for example 0.01 M sodium diethyl dithiocarbamate), to preparations in 0.05 M
Tris-HCl buffer, pH 8.1.
The purification method employs a high pH step to dissociate virus particles
from rapidly sedimenting material. Clarification is achieved by sedimentation
through 55% sucrose.
The following modification (D. Cartwright, unpublished data) of the original
Randles et al. (1976)
yields up to 20 mg of virus per kg of
N. debneyi leaf. Blend tissue with 3 vol. 0.067 M phosphate buffer (pH
5.6; containing 0.01 M sodium diethyl dithiocarbamate and 0.05% thioglycerol),
strain through muslin and centrifuge at 12,000 g for 20 min.
Resuspend the pellet in 0.05 M glycine buffer (pH 9.0; containing 0.05%
thioglycerol), stir 4-6 h. Clarify at 2500 g for 20 min, layer
over 55% sucrose containing 0.05% thioglycerol, and centrifuge at 176,000
g for 90 min. Resuspend the pellet in 1-2 ml 0.05% thioglycerol
for 16 h. Clarify and centrifuge again through 55% sucrose, resuspend for 2 h
and centrifuge through a 10-40% linear sucrose gradient (buffered with 0.05 M
glycine, pH 9.0) at 74,000 g for 25 min. Recover the very broad
light-scattering zone and sediment the virus at 176,000 g for 40
min. Work at 4°C.
Properties of Particles
Ultraviolet absorption spectrum shows a minimum at 248-250 nm, maximum at
Particles are straight rods, 18-19 nm in diameter
purified preparations most particles are 100-175 nm long. However, the length
distribution is broad with the frequency of particles in the smaller size classes
increasing during purification to give a peak in the 125-150 nm class. This
suggests that particles are either fragile, or undergo progressive dissociation
of end-to-end aggregates during purification. Particles have helical symmetry,
with a pitch of 2.86 ± 0.03 nm when stained in ammonium molybdate or
Particle CompositionNucleic acid
: Nucleic acids extracted from infected leaf show a
zone of infectivity between 15 S and 33 S when sedimented in
sucrose density gradients. Infectivity of these extracts is lost upon
treatment with ribonuclease A (1 µg/ml). Nucleic acid extracts from
purified virus show a 2.3 x 106
M. Wt component and up to 8 smaller
minor species when fractionated on polyacrylamide gels (D. Cartwright,
Protein: Subunits have M. Wt of 2.14 x 104.
Other components: None known.
Relations with Cells and Tissues
Particles were not seen in locally or systemically infected tissue, and
no intracellular changes have been observed.
mosaic virus resembles the seedborne rod-shaped
barley stripe mosaic virus
(Atabekov & Novikov, 1971
and also the
potato mop-top virus
soil-borne wheat mosaic virus
beet necrotic yellow vein virus
peanut clump virus
(Thouvenel, Dollet & Fauquet, 1976
However, it is distinguishable from these by its host
range, efficient seed transmissibility in some Nicotiana
particle instability and serological uniqueness. A useful test which distinguishes
it from all the above viruses is its ability to infect Nicotiana
and Gomphrena globosa,
but not Tetragonia expansa
- Atabekov & Novikov, CMI/AAB Descriptions of Plant Viruses 68, 4 pp., 1971.
- Brakke, CMI/AAB Descriptions of Plant Viruses 77, 4 pp., 1971.
- Harrison, CMI/AAB Descriptions of Plant Viruses 138, 4 pp., 1974.
- Putz, J. gen. Virol. 35: 397, 1977.
- Randles, Harrison & Roberts, Ann. appl. Biol. 84: 193, 1976.
- Tamada, CMI/AAB Descriptions of Plant Viruses 144, 4 pp., 1975.
- Thouvenel, Dollet & Fauquet, Ann. appl. Biol. 84: 311, 1976.
Figs 1, 3, 6, and 7 by courtesy of Scottish Horticultural Research
Systemically infected Gomphrena globosa.
Systemic mosaic and distortion in Nicotiana glutinosa
Systemically infected Beta macrocarpa leaf.
Chlorotic local lesions in Chenopodium quinoa.
Systemic chlorosis, interveinal necrosis and leaf distortion of
Virus particles from a purified preparation, stained with 2%
ammonium molybdate. Bar represents 200 nm.
Helical structure of virus particles; stained with uranyl formate.
Bar represents 100 nm.