Tomato spotted wilt virus
T. S. Ie
Laboratorium voor Virologie, Binnenhaven, Wageningen, The Netherlands
Described by Samuel, Bald & Pittman (1930),
Klinkowski & Uschdraweit (1952),
reviewed by Best (1968).
- Kromnek virus (Rev. appl. Mycol. 13: 124)
- Lycopersicum virus 3 (Rev. appl. Mycol. 36: 303)
- Pineapple yellow spot virus (Rev. appl. Mycol. 11: 116; 11: 586; 19: 483)
- Tomato bronze leaf virus (Rev. appl. Mycol. 30: 450)
- Vira cabeça virus (Rev. appl. Mycol. 20: 501; 45: 756)
An RNA-containing virus with membrane-bound isometric particles 70-90 nm in
diameter. It is transmitted by thrips and by inoculation of sap, has a very
wide host range and is common in temperate and subtropical regions throughout
Causes a range of chlorotic, necrotic, stunting and enation symptoms in
all parts of its many hosts. The bronzing symptoms in tomato leaves
and the one-sided growth (kromnek) of tobacco and tomato are characteristic.
Leaf enations occur in Dahlia,
flower deformations and colour breaking of
the petals in Dahlia
The great variability in symptom
expression is probably largely due to the complex of mixed strains.
Common in temperate and subtropical regions throughout the world.
Host Range and Symptomatology
Host range is very wide; found in 166 plant species in 34 families, including
7 monocotyledonous families
(Klinkowski & Uschdraweit, 1952
Easily transmissible by inoculation of sap using abrasives,
especially when extracts are made in neutral buffer, containing reducing agents.
Petunia hybrida cvs. Pink Beauty and Minstrel. Local necrotic lesions 2-4
days after inoculation; not systemic (Fig.2).
Nicotiana tabacum cv. Samsun NN (tobacco), N. clevelandii and
N. glutinosa. Local necrotic lesions, followed by systemic necrotic
patterns and leaf deformation.
Cucumis sativus (cucumber). Cotyledons develop local chlorotic spots
with necrotic centres, 4-5 days after inoculation (Fig.3).
Vinca rosea. Local black spots, 10-14 days after inoculation, leaves
sometimes yellowing and abscissing; systemic mosaic and deformation.
Tropaeolum majus. Inoculated leaves symptomless; after 8-12 days a
systemic mosaic pattern of yellow and dark green specks develops (Fig.5),
sometimes also with necrotic spots.
Tropaeolum majus and Gomphrena globosa are suitable plants for
maintaining cultures. Leaves with symptoms contain much virus and are good
inoculum sources. Good sources of virus for purification are the systemically
infected leaves of Nicotiana rustica and N. glutinosa.
Petunia hybrida (cvs. Pink Beauty and Minstrel) is the best local lesion
host. Local necrotic lesions 2-3 days after inoculating plants in the glasshouse,
but also in detached leaves in Petri dishes under artificial illumination
(Selman & Milne, 1961).
Many minor variants, giving symptoms differing in severity, have been
isolated. The most stable and important of these are: strains TB
of Norris (1946)
strains A, B, C1, C2, D,
of Best (1968)
); and the
tomato tip blight
(McWhorter & Milbrath, 1935
Transmission by Vectors
Transmitted by the thrips Thrips tabaci, Frankliniella schultzei,
and F. fusca
virus is acquired by the larvae but not by the adults, whereas only adults
transmit. Thus transmission is only by adults that fed on infected plants in the larval stage
(Bald & Samuel, 1931
). Shortest reported acquisition
period is 15 min for T. tabaci.
Latent (incubation) period is 4-10 days,
depending on the vector species. Vectors are maximally infective 22-30 days
after acquisition but sometimes retain the virus for life. They do not transmit virus to their progeny.
Transmission through Seed
Reported (96%) in Cineraria
found only 1% infection; the virus is apparently carried in the testa, not in the embryo.
Transmission by Dodder
Antisera of good titre are still not available.
Best & Hariharasubramanian (1967)
prepared an antiserum with a titre of 1/256 in precipitin tests.
Feldman & Boninsegna (1968)
obtained an antiserum with a titre of only
1/10 in gel-diffusion tests, using heated (70°C) infective sap as immunogen.
Stability in Sap
Physically and chemically one of the most unstable plant viruses. In sap,
the thermal inactivation point (10 min) is 40-46°C, longevity in vitro
at room temperature is 2-5 hr and dilution end point between 2 x 10-2
. Infectivity rapidly falls at pH values below pH 5, and
is maintained best at pH values near pH 7. It is greatly stabilized in plant
extracts by adding reducing agents such as 0.01 M Na2
or Na thioglycollate.
Because of its extreme instability in vitro,
purification of tomato
spotted wilt virus is still a problem.
1. Best (1968).
Extract 100 g systemically infected Nicotiana glutinosa
leaves in 500 ml ice-cold 0.01 M phosphate buffer (pH 7) containing
Na2SO4 (0.07 M), Na2SO3 (0.01 M)
and sodium diaminoethane-tetraacetate (Na-EDTA) (1 x 10-4 M).
Concentrate and purify the virus by differential centrifugation and one or
two cycles of sucrose density gradient centrifugation. Yields are about 1 mg
virus per 100 g tissue.
2. Black, Brakke & Vatter (1963).
Extract 100 g systemically infected
Nicotiana rustica leaves in 200 ml ice-cold 0.1 M potassium phosphate
buffer pH 7, containing Na2SO3 (0.01 M). In this high
ionic strength buffer, most of the infectivity is sedimented by low speed
centrifugation (c. 1700 g for 30 min). Resuspend in 0.01
M Na2SO3 and concentrate by differential centrifugation.
Sucrose density gradient centrifugation gives a visible zone with which most
of the infectivity is associated. This method does not always give good results
because it takes 8-10 hr and the virus is very unstable.
Van Kammen, Henstra & Ie (1963)
using nearly the same method as Black et al. confirm
their experiences. The purified virus is not sufficiently free of cellular
contaminants and the virus particles sometimes show a typical tail-like
Properties of Particles
Sedimentation coefficient (s20,w
): 530 S
); 583 S
(Black et al., 1963
Particles approximately isometric, c.
70-90 nm in diameter,
apparently bounded by a membrane
). The structure of the material
inside the membrane is uncertain. The outer layer of the membrane seems to
consist of a nearly continuous layer of projections c.
5 nm thick,
which stain more densely than the membrane itself. Purified particles
sometimes show a tail-like extrusion (Fig.7
Particle CompositionBest (1968)
reported preliminary experiments which suggested that the
particles contain about 20% lipid, 7% carbohydrate and 5% RNA, with the unusual
base composition (molar percentage of nucleotides) of G38; A35; C9; U19. The
proportions of the usual amino acids fall within the range found for other
viruses except that the lysine and histidine content is high.
Relations with Cells and Tissues
In the plant cell, the characteristic particles of tomato spotted wilt
virus occur as clusters in cytoplasmic vacuoles, which are possibly cisternae
of the endoplasmic reticulum (Fig.8
Milne & De Zoeten, 1967
and in the dilated lumen of the nuclear membrane
They have not so far been found in other cell organelles. The virus particles
are found in the cells of roots, stems, leaves and petals. In the anthers of
they occur only in the endothecium tissue but never
in the tapetum layer or in the pollen cells. In newly infected cells of young
leaf tissue, typical dense masses occur in the cytoplasm between the ribosomes,
sometimes in big complexes located near the nucleus. These dense masses are
striated with a periodicity of about 5 nm (Ie, unpublished). The typical
electron dense particles scattered singly between the ribosomes
no relationship at all with TSWV, but are normal constituents of the cells of
some cultivars of Tropaeolum majus.
- Bald & Samuel, Bull. Coun. scient. ind. Res., Melb. 54, 24 pp., 1931.
- Best, Adv. Virus Res. 13: 66, 1968.
- Best & Hariharasubramanian, Enzymologia 32: 128, 1967.
- Black, Brakke & Vatter, Virology 20: 120, 1963.
- Crowley, Aust. J. biol. Sci. 10: 449, 1957.
- Fawcett, Revta ind. agric. Tucumán 30: 221, 1940.
- Feldman & Boninsegna, Nature, Lond. 219: 183, 1968.
- Ie, Neth. J. Pl. Path. 70: 114, 1964.
- Jones, Phytopathology 34: 941, 1944.
- Kitajima, Virology 26: 89, 1965.
- Klinkowski & Uschdraweit, Phytopath. Z. 19: 269, 1952.
- McWhorter & Milbrath, Phytopathology 25: 897, 1935.
- McWhorter & Milbrath, Stn Circ. Ore. agric. Exp. Stn 128, 14pp., 1938.
- Milne, J. gen. Virol. 6: 267, 1970.
- Milne & De Zoeten, J. Ultrastruct. Res. 19: 398, 1967.
- Norris, Bull. Coun. scient. ind. Res., Melb. 202, 51 pp., 1946.
- Sakimura, Pl. Dis. Reptr 45: 766, 1961.
- Sakimura, in Biological transmission of disease agents, Ed. K. Maramorosch, New York, Academic Press, 1962.
- Samuel, Bald & Pittman, Bull. Coun. scient. ind. Res., Melb. 44, 64 pp., 1930.
- Selman & Milne, Pl. Path. 10: 100, 1961.
- Smith, Textbook of Plant Virus Diseases, 572 pp., London, Churchill, 1957.
- Van Kammen, Henstra & Ie, Virology 30: 574, 1966.
Photographs: Courtesy of Laboratory of Virology, State Agricultural University, Wageningen.
Systemically infected tomato leaves. Yellow specks and beginning of
small necrotic spots, resulting in the typical bronzing symptoms. Top leaves
Local necrotic lesions in Petunia leaf, 3 days after inoculation.
Local chlorotic lesions with necrotic centres in cucumber cotyledon,
5 days after inoculation.
Virus particles in an ultrathin section of a tomato leaf cell. Embedded
in methacrylate, fixed with glutaraldehyde and OsO4, stained with
uranyl acetate and lead citrate.
Systemic symptoms in Tropaeolum majus leaves. Sometimes necrotic spots also appear.
Systemically infected older tomato leaves with obvious yellow and
necrotic spots. Distorted young fruit.
Purified virus particles, fixed with OsO4 and stained
negatively with phosphotungstate. Note the tail-like extrusion. Bar represents 100 nm.
Ultrathin section of a leaf cell of systemically infected
Tropaeolum majus. In the cytoplasm, the virus clusters are located in
vacuoles, possibly the cisternae of the endoplasmic reticulum.