Wheat streak mosaic virus
M. K. Brakke
Agricultural Research Service, US Department of Agriculture, Plant Pathology Department, University of Nebraska, Lincoln, Nebraska, USA
Described by McKinney (1937).
- Wheat viruses 6 and 7 (McKinney, 1937)
- Marmor virgatum (Rev. appl. Mycol. 24: 136)
- American Type Culture Collection Numbers AC29, AC85, PV57 and PV91
A mite-transmitted cereal virus with filamentous particles c. 700 nm long and 15 nm in
diameter, containing RNA. Readily sap-transmissible
and gives symptoms at all temperatures above 10°C at which wheat grows.
Causes a severe mosaic of winter wheat and certain millets, and a mild mosaic in some varieties of
maize. The disease causes serious losses
in wheat infected in the autumn, producing severe stunting
), varying degrees of necrosis and
death of tillers, and reduced seed set and seed weight (McKinney, 1967
USA, Canada, Jordan, Rumania, Yugoslavia and Russia
Host Range and Symptomatology
Infects most or all varieties of wheat (Triticum aestivum),
oats (Avena sativa),
barley (Hordeum vulgare),
and rye (Secale
and some varieties of maize (Zea mays
) and millets (Panicum, Setaria,
spp.). Infects many wild
grasses, including species of Aegilops, Bromus, Digitaria, Echinochloa, Eragrostis, Haynaldia,
Hordeum, Lolium, Panicum, Phalaris, Setaria, Cenchrus, Agropyron, Bouteloua, Elymus, Oryzopsis, Poa
No dicotyledons have been infected
(Sill & Agusioba, 1953
Sill & Conin, 1953
- Gives systemic mosaic symptoms, often accompanied by stunting, at both warm and cool temperatures
in almost all varieties of wheat (Fig.2), oats and barley,
and some varieties of maize. Does not
systemically infect Agropyron repens, Bromus inermis, Saccharum officinarum (sugar cane),
Sorghum bicolor (sorghum) or Hordeum jubatum.
- Wheat. Mildew-resistant varieties such as Michigan Amber and Kent are frequently used.
- No satisfactory local-lesion assay host known. Systemic assays may be done with wheat. Vector
transmission tests should be done with wheat, which is the best host for the mite.
Many variants can be selected on the basis of symptom severity, but few studies have been done
on such strains.
selected a mild strain (AC85, Catalogue of Plant Viruses, 1958,
American Type Culture Collection; No. PV91 in current ATCC collection) for use in interference or
Transmission by Vectors
Transmitted by adult and all nymphal stages of the eriophyid mite, Aceria tulipae
but can only be acquired from plants by nymphs. They acquire the virus in feeding periods of 15 min or
more. The virus persists for at least 9 days in infective mites kept on virus-immune plants. The virus
does not pass from the adult mite to its progeny through the egg
Staples & Allington, 1956
Transmission through Seed
The virus is a good antigen: antisera with microprecipitin titres of 1/256-1/1024 have been
prepared by injecting rabbits with about 5 mg purified virus. The precipitin test is not always reliable
with unconcentrated plant sap because the virus concentration is low, but it is reliable when the
virus is first concentrated by centrifugation. Gel-diffusion tests work better when the virus is
by treatment with a detergent
(Brakke & Ball, 1968
). The leaf-dip
serological method works well
(Ball & Brakke, 1968
Its particles resemble those of
hordeum mosaic viruses; the
first two viruses are transmitted by another eriophyid mite, Abacarus hystrix.
the available antisera, which are comparatively low-titred, no serological relationship has been found
between these viruses. Agropyron mosaic virus systemically infects Agropyron repens,
hordeum mosaic virus infects Hordeum jubatum,
but neither of these species is infected
systemically by wheat streak mosaic virus.
Stability in Sap
Thermal inactivation point in wheat sap (10 min) is 54°C; dilution end-point is
. Survives for 4 days but not 8 days in wheat sap at 20°C, and
for 1 month, but not 2 months, at 2°C. Can be kept at least 16 years in desiccated leaves over
at 2°C (McKinney et al
As with other viruses of similar morphology, the results of attempted purification are often
erratic, but the following procedure gives consistent results
(Brakke & Ball, 1968
). The two
youngest leaves of infected wheat are harvested about 10 days after inoculation and ground with
2 ml of 0.01 M K2
per g leaf. The homogenate is adjusted to pH 6.0-6.1,
kept for 1 h at 40°C, clarified by low speed centrifugation, adjusted to pH 8.0 and, after
adding citrate to a concentration of 0.01 M, centrifuged for 2.25 h at 68,000 g
The pellet is suspended in 0.01 M sodium citrate, pH 8.0, and the virus further purified by
centrifugation first through a gradient column of 100-400 mg of sucrose per ml dissolved in 0.01 M
sodium citrate, pH 8.0, and then through a gradient column of 200-600 mg of sucrose per ml dissolved
in pH 6.5, 0.1 M Tris(hydroxy-methyl)aminomethane, 0.032 M citric acid, 0.1 mM bis(3-aminopropyl)amine,
and 1/500 normal rabbit serum. The virus zones are collected, freed of sucrose by dialysis against
the pH 6.5 buffer without serum, and the virus concentrated by ultracentrifugation. The average yield
is about 1.2 A254
units (approximately 0.4 mg) from 100 g leaf, i.e.
the virus detectable in clarified sap.
The virus has also been purified by differential centrifugation from pH 5.0 clarified sap of
leaves previously frozen for 1 day (Slykhuis & Bell, 1965).
Properties of Particles
Sedimentation coefficient (s20, w
) about 165 S at small concentrations
in sucrose gradients.
(Brakke & Van Pelt, 1968).
Infective particles are 700 nm long
). Shorter particles of differing lengths are usually
present, but there is no indication that these are infective.
May be prepared by treating virus at 2°C with 1% sodium dodecyl sulphate in pH
9.0, 0.1 M ammonium carbonate, 0.001 M EDTA, containing 100-500 µg/ml bentonite, followed by
density gradient centrifugation. Phenol and salt methods have not been successful. The particle
contains a single molecule of RNA with a sedimentation coefficient (s20, w
) in 0.15
M NaCl, 0.015 M sodium citrate, pH 7.0, of 40 S (measured at 14°C in sucrose gradients).
The M. Wt of the RNA is 2.8 x 106
, calculated from its sedimentation coefficient after
formaldehyde treatment. Susceptibility to RNase at high salt concentration and reactivity with
formaldehyde suggests that the RNA is single-stranded.
Protein: No information.
Relations with Cells and Tissues
Inclusion bodies containing virus particles are visible by electron microscopy but not by light
microscopy. They are found in all the different types of cells in the leaf. Pinwheel inclusions are
also found, but these probably do not contain virus. When normal components of some cells are disrupted
during fixation and embedding, pinwheels may still be present, but not the virus-containing inclusion
bodies (Shepard & Carroll, 1967
W. G. Langenberg, unpublished).
An experienced observer can identify plants infected with wheat streak mosaic virus in the field
by the general pattern of their distribution in the crop, together with their symptoms and the
presence of mites, but symptoms on individual plants are not reliable for identification. Other
viruses giving similar mosaics differ from wheat streak mosaic virus in the following ways: the
soil-borne wheat mosaic
do not give symptoms at 25°C and above; the leafhopper-transmitted
viruses are not sap-transmissible;
brome mosaic virus
kills Golden Giant sweet corn and infects
and both brome mosaic and
barley stripe mosaic
viruses have higher thermal
inactivation points. None of the above viruses have long flexuous particles and they can be easily
distinguished from wheat streak mosaic virus by leaf-dip electron microscopy. Other viruses in wheat
that have long, flexuous particles and are mite-transmitted may be distinguished from wheat streak
mosaic virus by host range (see Relationships).
- Ball & Brakke, Virology 36: 152, 1968.
- Brakke & Ball, Phytopathology 58: 963, 1968.
- Brakke & Van Pelt, Analyt. Biochem. 26: 242, 1968.
- McKinney, Circ. U.S. Dep. Agric. 442, 23 pp., 1937.
- McKinney, J. Wash. Acad. Sci. 34: 322, 1944.
- McKinney, Pl. Dis. Reptr 40: 898, 1956.
- McKinney, in Wheat and Wheat Improvement, ed. K. S. Quisenberry & L. P. Reitz, Am. Soc. of Agronomy, Madison, Wisconsin, USA., pp. 355-374, 1967.
- McKinney, Silber & Greeley, Phytopathology 55: 1043, 1965.
- Shepard & Carroll, J. Ultrastruct. Res. 21: 145, 1967.
- Sill & Agusioba, Pl. Dis. Reptr 39: 633, 1953.
- Sill & Conin, Trans. Kans. Acad. Sci. 56: 411, 1953.
- Slykhuis, Phytopathology 45: 116, 1955.
- Slykhuis, Rev. appl. Mycol. 46: 401, 1967.
- Slykhuis & Bell, Can. J. Bot. 44: 1191, 1965.
- Staples & Allington, Res. Bull. Neb. agric. Exp. Stn 178, 40 pp., 1956.
A much stunted infected wheat plant in the field.
Wheat leaves; (left) healthy; (centre and right) two leaves showing symptoms
Wheat leaf infested with the mite vector, Aceria tulipae. Bar represents 0.5 mm.
Virus particle in a mixture of potassium phosphotungstate and potassium vanadatomolybdate.
Bar represents 100 nm.