Foxtail mosaic virus
Margaret N. Short
John Innes Institute, Colney Lane, Norwich NR4 7UH, England
- Described by
Paulsen & Sill (1969) and
Paulsen & Niblett (1977).
A virus with slightly flexuous filamentous particles with a modal length of c.
500 nm, containing one coat protein species and one molecule of single-stranded RNA.
Experimental host range fairly broad, many species being infected symptomlessly. No
insect vector known. Reported only from the USA where the diseases caused are of no
Main DiseasesSystemic mosaic in Setaria viridis and S. italica
(Paulsen & Niblett, 1977).
Geographical DistributionReported only from USA.
Host Range and SymptomatologyTransmitted by manual inoculation to 56 out of 68 species of Gramineae
(Paulsen & Niblett, 1977)
and to 41 species in 11 dicotyledonous families
(Paulsen & Niblett, 1977;
In many species infection is symptomless and/or confined
to inoculated leaves, but the virus induces systemic mosaic in wheat, oats and barley
- Chenopodium amaranticolor. Pin-point necrotic local lesions
by systemic necrotic etch and then mosaic.
- Gomphrena globosa. Necrotic local lesions; no systemic infection.
- Nicotiana clevelandii. Necrotic and chlorotic local lesions followed by
- Pisum sativum cv. Meteor. Necrotic local spots and rings
- Tetragonia expansa. Necrotic local lesions followed by systemic mosaic.
- Barley is a long-lived propagation host and a good source of virus for purification.
- Chenopodium amaranticolor is a suitable host for local lesion assays.
Transmission by VectorsNo reports.
Transmission through SeedPaulsen & Niblett (1977)
reported 2% seed transmission in Briza maxima
and 1% in Avena sativa.
Transmission by DodderThe virus was not transmitted by Cuscuta campestris parasitic on
Chenopodium quinoa, Hordeum vulgare or Nicotiana clevelandii; no virus
was detected by back-inoculation from the dodder vines
SerologyThe virus is strongly immunogenic: positive reactions were observed in ring
interface precipitin tests with antiserum diluted to 1/1024
RelationshipsIn ring interface precipitin tests, antiserum to foxtail mosaic virus reacted with
purified preparations of two
narcissus mosaic and
viola mottle viruses,
but not with preparations of five others:
(barrel cactus strain),
clover yellow mosaic,
potato X or
white clover mosaic viruses
Stability in SapRelatively stable in extracted sap, with a dilution end-point of 10-6 to
10-7 and a thermal inactivation point of 68°-70°C when heated for
10 min. Virus remained infective for 46 days in undiluted sap at room temperature, and
for 105 days in buffered extract
(Paulsen & Niblett, 1977).
PurificationPurified virus is readily prepared by the method devised by
Bancroft, Abou Haidar & Erickson (1979)
clover yellow mosaic virus.
Grind fresh or frozen leaves of
Hordeum vulgare in 0.02 M sodium borate buffer, 0.01 M fresh ascorbic acid,
pH 8.2, and clarify the extract with 0.5% Triton X-100. Ultracentrifuge the virus
through 5 ml cushions of 30% sucrose in 0.01 M Tris-HCl, 0.001 M EDTA, pH 8.0.
Resuspend the virus in the same buffer and purify further by differential centrifugation.
Yields of 0.5 mg virus per gram leaf tissue were obtained from selected fresh leaves
of Hordeum vulgare.
Properties of ParticlesIn linear-log sucrose gradients, purified virus particles sediment as two
u.v.-absorbing, infective components
(Paulsen & Niblett, 1977)
coefficients of 122 S and 144 S and
A260/A280 = 1.2.
Both components contain a single RNA species with a sedimentation coefficient of
32 S which suggests that the 144 S component is a dimer of the 122 S
Particle StructureSlightly flexuous filamentous particles with helical symmetry and a modal length of
c. 500 nm when negatively stained with potassium phosphotungstate, pH 6.4
From optical diffraction studies,
Richardson, Tollin & Bancroft (1981)
helix pitch of 3.5 nm, with 8.8 subunits per turn; the structural parameters for foxtail
mosaic virus were typical of members of the
Particle CompositionNucleic acid: Single-stranded RNA with a M. Wt of about 2.03-2.24 x 106
(Paulsen & Niblett, 1977),
estimated by sedimentation with RNA standards in
linear-log sucrose density gradients in 0.02 M phosphate buffer, pH 6.25. The RNA
comprises about 7% of the particle weight, calculated from the data on particle
structure and the RNA and coat protein subunit M. Wts.
Protein: Coat protein can be prepared by disrupting the virus in 1 M HCl.
A subunit of M. Wt 21,171 was calculated from the amino acid composition and two-dimensional
peptide map. The subunit polypeptide chain has 192 amino acid residues, comprising 13 lys,
1 his, 9 arg, 2 trp, 25 asp, 16 thr, 9 ser, 20 glu, 14 pro, 7 gly, 27 ala, 2 cys, 11 val,
3 met, 7 ile, 11 leu, 7 tyr, 8 phe
Relations with Cells and TissuesLarge clusters of parallel particles occur in the cytoplasm of infected cells of
No inclusion bodies or other virus-induced
structures have been observed (K. A. Plaskitt, unpublished data).
NotesAt least 10 other viruses are readily mechanically transmissible to barley. However,
these have either isometric particles (e.g.
cocksfoot mild mosaic,
cocksfoot mottle and
panicum mosaic viruses),
flexuous filamentous particles 700 nm or
Guinea grass mosaic,
sugarcane mosaic and
wheat streak mosaic viruses),
or rigid rod-shaped particles
barley stripe mosaic,
poa semi-latent and
soil-borne wheat mosaic viruses).
Furthermore none of these viruses has been reported
to occur naturally in Setaria spp., nor to infect Pisum sativum or
Nicotiana clevelandii, and they can therefore easily be distinguished from
foxtail mosaic virus by electron microscopy and host range studies. Foxtail mosaic virus
has not been reported to occur naturally in barley.
- Bancroft, Abou Haidar & Erickson, Virology 98: 121, 1979.
- Paulsen & Niblett, Phytopathology 67: 1346, 1977.
- Paulsen & Sill, Phytopathology 59: 1942, 1969.
- Richardson, Tollin & Bancroft, Virology 112: 34, 1981.
- Short, Rep. John Innes Inst. for 1980: 126, 1981.
- Short, Ph.D. Thesis, University of East Anglia, 1982.
Systemically infected leaves of Hordeum vulgare cv. Maris Otter.
Necrotic local lesions in Chenopodium amaranticolor.
Necrotic local spots and rings in Pisum sativum cv. Meteor.
Electron micrograph of virus particles in a leaf-dip of Nicotiana
clevelandii, negatively stained in potassium phosphotungstate (courtesy G.
J. Hills). Bar represents 100 nm.
Electron micrograph of a leaf-section of Nicotiana clevelandii
containing clusters of virus particles, stained in uranyl acetate (courtesy K. A.
Plaskitt). Bar represents 500 nm.