Tomato mosaic virus
Glasshouse Crops Research Institute, Littlehampton, Sussex BN16 3PU, England
Instituut voor Plantenziektenkundig Onderzoek, Binnenhaven 12, Postbus 42, Wageningen, The Netherlands
- Many synonyms have been used (see
virus 1 (Rev. appl. Mycol. 36: 303); see also under Strains
An RNA-containing virus, widespread and economically damaging in glasshouse and
outdoor tomato crops in many countries. The virus is readily spread by handling and cultural
operations; it also contaminates seeds and soil, but no natural vector is known. It is readily
sap-transmissible to a fairly wide range of herbaceous plant species. The infective particles
are straight rods c. 300 x 18 nm.
Widespread and often epidemic in tomato (Lycopersicon esculentum
Disease symptoms are greatly influenced by temperature, daylength, light intensity, age of
plant, virus strain and cultivar of tomato
(Ainsworth & Selman, 1936
Broadbent & Cooper, 1964
Crill et al., 1973
Fletcher & MacNeill, 1971
Symptom types can be broadly grouped as:
1. Light and darker green mosaic leaf mottle, sometimes with distortion of
this is the most common reaction in summer in glasshouses. In winter, with low light
short days and temperatures not above 20°C, plants are often severely stunted and
distorted to fern-leaf or tendril shape, but mottling may be slight.
Plants are less vigorous,
and fruit yield is reduced by 3 to 23%
2. Conspicuous yellow or aucuba mosaic leaf mottling
may also affect the fruit
3. Necrosis of stems, petioles, leaves and/or fruit.
single virus streak, consists of longitudinal necrotic streaks on stems or
killing the plant; fruits develop large sunken necrotic lesions. Streak can occur at
or below, with certain strains of the virus
(Komuro et al., 1966),
but can rarely be
reproduced experimentally by sap-inoculation
although easily by grafting
(van Dorst, 1963).
Double virus streak
caused by mixed infection with
potato virus X
plus almost any strain of tomato mosaic virus
(Valleau & Johnson, 1930),
more destructive than single virus streak, and the fruits are disfigured by
necrotic lesions that later become sunken
Internal necrosis or bronzing in
fruits results from infection with certain tomato mosaic virus strains when the fruits are
Boyle & Bergman, 1967;
Boyle & Wharton, 1957),
is distinguished from blotchy ripening
(Jenkins et al., 1965;
may also be associated with tomato mosaic virus infections.
Ribgrass mosaic virus can
also induce fruit necrosis
Other isolates of tomato mosaic virus cause
winter necrosis, summer necrosis or crusty fruit diseases
Sweet pepper (Capsicum frutescens) grown after affected tomato crops may
show severe leaf necrosis and abscission, chronic mosaic and stunting
Tomato mosaic virus strains occur in Chenopodium murale in the USA, causing
severe stunting, distortion and necrosis
(Bald & Paulus, 1963),
and in pear (Pyrus
calleryana) associated with a diffuse chlorotic leaf spotting
(Opel et al., 1969).
World-wide, wherever tomatoes are grown.
Host Range and Symptomatology
Many solanaceous species are susceptible to the virus; most suscepts produce
necrotic local lesions, sometimes followed by systemic mosaic-mottling and necrosis.
Most species tested in the families Aizoaceae, Amaranthaceae, Chenopodiaceae and
Scrophulariaceae are also susceptible (M. Hollings, unpublished data).
- Nicotiana glutinosa. Dark, necrotic local lesions, initially 0.5 mm diameter,
to c. 4 mm. Systemic invasion occurs at 33°C (M. Hollings, unpublished data),
but different strains induce different symptoms: chlorosis and stunting; necrotic flecks and
leaf distortion; or spreading necrosis. All strains are usually lethal within 1-2 weeks.
- Several Nicotiana spp. have been used to distinguish tomato mosaic virus
strains from the type strain
or tobacco forms of the virus,
though none is infallible.
- N. tabacum, White Burley type. Different selections respond very differently
(Kassanis & Selman, 1947).
In the necrotic or Dutch A selection
(Termohlen & van Dorst, 1959;
most typical tomato mosaic virus isolates induce necrotic
local lesions in 3-4 days
without systemic invasion, but some (including dahlemense,
Ohio I, II and III strains) invade systemically
(M. Hollings, unpublished data).
- N. sylvestris. Local lesions with no systemic invasion
(Komuro et al., 1966;
Wang & Knight, 1967;
M. Hollings, unpublished data).
- N. rustica. Reported to react with necrotic local lesions only with all 18
tobacco mosaic virus strains
induce systemic mottle and necrosis.
But 5 of 22 isolates (including dahlemense, Ohio I, II and III) caused systemic mottle and
necrosis similar to tobacco isolates (M. Hollings, unpublished data).
- N. clevelandii x N. glutinosa hybrid
Gives only necrotic local
lesions with eight of 22 tomato isolates (M. Hollings, unpublished data), and systemic lethal
necrosis with 14 isolates.
- Datura stramonium. Necrotic local lesions after 2-3 days,
with no systemic infection.
- Phaseolus vulgaris cv. Scotia. Some isolates
(including dahlemense, Ohio I and II)
induce reddish necrotic local lesions in 3-6 days in primary leaves,
but others do not infect this
plant (M. Hollings, unpublished data). Tobacco mosaic virus strains induce local lesions.
- Chenopodium spp. Chlorotic or necrotic local lesions (4-10 days) in C.
amaranticolor, C. murale and C. quinoa
Systemic pale green or necrotic
flecks and mottle in C. murale; most isolates behave likewise in
and some do in C. quinoa. Systemic symptoms ranged from severe to none, and were
not distinguishable from those induced by tobacco mosaic virus
(M. Hollings, unpublished data).
- Gomphrena globosa. Necrotic or semi-necrotic local lesions in c. 1 week;
most isolates induce systemic chlorotic mottle.
- Tetragonia expansa. Chlorotic local lesions in 7-10 days, subsequently enlarging
to characteristic necrotic-edged lesions. Some isolates invade systemically,
with or without symptoms.
- Some tomato isolates cause symptomless infection in inoculated leaves of Brassica
pekinensis or cotyledons of Cucumis sativus cv. Butchers Disease Resister.
infection in Phaseolus vulgaris cv. The Prince or Vigna sinensis cv. Blackeye.
- Tobacco mosaic virus, in contrast to tomato mosaic virus, typically induces systemic
disease in N. sylvestris, N. tabacum White Burley necrotic selection, and
- Nicotiana clevelandii. Small plants are rapidly killed and yield little virus;
develop necrotic local lesions followed by systemic rosetting and crinkling,
with severe general
chlorosis. High yields of virus are obtained, but plants are usually killed in 2-4 weeks.
is unsuitable for propagating or maintaining the virus because it gives low yields,
contain more impurity, and it can selectively change the character of isolates (see below).
Cultures are best maintained at -20°C in leaves or sap.
- Nicotiana glutinosa is widely used; N. tabacum cvs. Xanthi-nc or Samsun
NN, Chenopodium quinoa and C. murale are also suitable.
Many isolates of tomato mosaic virus are similar in amino acid composition, base
composition and buoyant density, and are serologically closely related
(Wang & Knight, 1967
Mosch et al., 1973
Dawson et al., 1975
data), although they may differ in symptomatology. A few isolates differ from the
amino acid composition or serological behaviour.
One way in which strains have been classified is by their ability to induce symptoms in
plants of certain Lycopersicon spp., or in isogenic lines of Craigella tomato
possessing resistance genes Tm-1, Tm-2 or Tm-22
(Clayberg et al., 1960;
Dawson et al., 1975).
Five Pelham groups were
defined by ability to overcome the genes specified: 0 (unable to overcome any resistance
genes), 1 (gene Tm-1), 2 (gene Tm-2), 1.2 (genes Tm-I and Tm-2),
22 (gene Tm-22). Thus, of the Ohio strains
(McRitchie & Alexander, 1963;
Cirulli & Alexander, 1969;
I and II are in
Pelham group 0, III is in group 1, IV in group 2, and V in group 1.2.
Common tomato mosaic isolates include representatives in all
Pelhams categories. Most
tomato isolates are of Pelham type 0; strain 22, able to overcome
Tm-22, has only recently been detected
Field isolates may
contain virus types in more than one group
and a strain may
change markedly on passage through some tomato genotypes
(Zitter & Murakishi, 1969;
Pelham et al., 1970;
MacNeill & Fletcher, 1971;
MacNeill & Boxall, 1974).
These categories are of more value to plant breeders than to virologists; they do not
coincide with groupings based on antigenic relatedness, differential reactions in
species, or symptoms in tomato. Nor do they fully equate with the system of
placed 115 virus isolates in four groups according to their reactions in
and clonal lines of certain Lycopersicon spp. Thus, 14 isolates of
Pelham type 0 were
serologically quite closely related to one another, as well as to most isolates in
1 (Pelham type strain 1, dahlemense and M II-16 strains), 2 and 1.2
(M. Hollings, unpublished
data). In contrast, strains Ohio I and II are very similar to
tobacco mosaic virus
in amino acid
(Dawson et al., 1975),
reactions in Nicotiana spp. and serological
behaviour (M. Hollings, unpublished data), but they differ from it in being well
adapted to tomato.
Strain Ohio III differed both from tobacco mosaic virus and from tomato mosaic virus
(Dawson et al., 1975),
and serological behaviour
unpublished data). Ohio strain IV, however, is very closely related to
Pelham type strain 2 (M.
Hollings, unpublished data). Using cross-protection tests,
Chiba 2, 3 and 4 with strain Ohio IV, and separated these from Ohio I, II, III and V.
Ohio I, II and IV
and Ohio III
(Rast, 1968) have been identified in Europe.
Strains have also been named from symptoms in tomato; these strains include:
Tomato aucuba mosaic strain
Henderson Smith, 1928);
Pelham type 0, 1 or 2 (M. Hollings & B. J. Thomas, unpublished data; B. H. MacNeill,
personal communication). Causes a conspicuous yellow or aucuba leaf mottle,
Tomato enation mosaic strain
causes leaf distortion and
tends to produce yellow mosaic mottling,
is in Pelham group 1, and reacts in Nicotiana test plants more like tobacco mosaic
virus (M. Hollings, unpublished data).
Yellow ringspot strain
induces yellow ringspots, and is of
Pelham type 0.
Winter necrosis strain
(Rast, 1975); Pelham type 2.
Summer necrosis strain
Pelham type 1. Possibly equates with tomato
streak strain of
Tomato crusty fruit strain
causes corky crusts on fruit; induces very
tiny local lesions in Nicotiana glutinosa, and is of Pelham type 0.
Tomato rosette strain
(Price & Fenne, 1951);
severe distortion and stunting
similar to hormone weedkiller damage.
Tomato black fleck strain
induces black necrotic leaf flecks.
Pelham type 0.
M II-16 strain
a nitrous acid mutant of low pathogenicity, widely
used for protective inoculation of tomato seedlings; Pelham type 1.
Transmission by Vectors
No natural specific vector known, although grasshoppers transmitted experimentally;
early reports of aphid transmission are now regarded as due to inoculation by means of
(Bradley & Harris, 1972
Man is the principal vector. Infection is most
often introduced into tomato or pepper crops through root infection from contaminated
and/or through contaminated
seedlings. From these infection foci, the virus is readily spread by leaf contact and cultural
Broadbent & Fletcher, 1966
Transmission through Seed
The virus is present in the external mucilage, testa and sometimes endosperm of tomato
seeds, but was not proved to be within the embryo
(Taylor et al., 1961
The percentage of contaminated seeds varies greatly in different fruits;
up to 94% of seeds may contain the virus
(van Winckel, 1965
Infection of seedlings
occurs during transplanting, but not if seedlings are undisturbed
The virus is readily eliminated from the outside of tomato seeds by soaking them for
20 min in 10% (w/v) Na3PO4 solution; all external and usually
all internal virus is eliminated by heat treatment of dry seeds (2-4 days at 70°C) without
impairing seed germination
Some samples of
infected seed lost all virus when stored 7 months in paper packets, but not when stored
(John & Soya, 1955);
seed samples with endosperm infection remained so
for at least 9 years
Transmission by Dodder
Yellow and green strains of the virus were transmitted in
winter, but rarely in
summer, by Cuscuta subinclusa
and two other Cuscuta
The virus is a fairly good immunogen; one intravenous, followed by two intramuscular
injections (with complete adjuvant), each of c.
3 mg virus, gave antisera
titres of 1/4000 to 1/16,000 (M. Hollings, unpublished data). The virus reacts satisfactorily
in precipitin (tube or micro), ring, and gel-diffusion (freshly prepared 0.8% Ionagar No. 2)
tests. One major precipitation line in gel is often accompanied by a second, weaker line
multiple precipitation lines are discussed by
Tomato mosaic virus is a characteristic member of the
strains are more closely related to type strain
tobacco mosaic virus
than to other tobamoviruses,
but can be differentiated from them all by differential host responses, serological reactions
and amino acid composition of the virus protein. The extent of serological relatedness
among several tobamoviruses was correlated with amino acid sequence homology
(van Regenmortel, 1975
In tomato, mild strains of tomato mosaic virus usually protect against more severe strains
(Boyle & Bergman, 1969;
tobacco mosaic virus, however, does not protect
against tomato mosaic virus in tomato
(Broadbent & Winsor, 1964),
nor does tomato
mosaic virus protect against tobacco mosaic virus in tobacco
Ribgrass mosaic virus
does not protect against tomato mosaic virus in tomato
Stability in Sap
In tomato sap, the virus loses infectivity after 10 min at 85-90°C, or after dilution to
. Nicotiana clevelandii
sap may still be
infective at 2 x 10-7
. In air-dried tomato leaf, the virus was still infective after
24 years at laboratory temperature
Sap retains infectivity for many months
at laboratory temperature and for several years at 0 to -2°C, although some isolates show
marked changes in virulence after such storage
Storage at -20°C, or after
lyophilisation, seems to prevent this.
Readily purified in large amounts (up to 160 mg virus/kg tissue being obtained with
most isolates; M. Hollings, unpublished data). A good method that requires no
is a modification of
Gooding & Heberts procedure (1967)
: harvest Nicotiana
plants 10-14 days after infection, freeze overnight, and homogenise in
0.05 M phosphate buffer (pH 7.4) containing 0.1% (v/v) thioglycollic acid (4 ml buffer/g
tissue). Squeeze out sap through cloth, add n
-butanol dropwise (9.3 ml/100 ml
juice) and shake for 45 min at laboratory temperature. Clarify (30 min centrifugation,
) and to the supernatant fluid add 4 g polyethylene glycol (PEG,
M. Wt 6000) per 100 ml supernatant fluid; stir until dissolved, and stand mixture c.
30 min, then sediment virus precipitate (15 min, 10,000 g
), and re-suspend
pellet in 0.01 M phosphate buffer (20 ml/100 ml of initial extractant). Clarify (15 min,
). Further purification can be obtained by a second precipitation
with PEG (add 4.0 g NaCl, then 4.0 g PEG/100 ml fluid and stir until dissolved); sediment
virus precipitate (15 min, 10,000 g
) and re-suspend pellet in 2 ml 0.01 M
phosphate buffer/100 ml initial extract; remove insoluble material by brief centrifugation
(5 min, 10,000 g
Considerably purer preparations can be made by application of 1.0 to 1.5 ml portions
of the above preparations to columns (85 x 1.5 cm) of controlled pore glass beads (70 nm
pore size; Sigma London Chemical Co. Ltd.), pretreated with PEG M. Wt 20,000 at 1%
(w/v) in 0.04 M phosphate buffer pH 7.0. The virus is eluted with 0.04 M phosphate buffer
(pH 7.0) and appears in the void volume, well separated from host material (M. Hollings
& R. J. Barton, unpublished data). The virus can be further concentrated by
precipitation with ethanol (2.5:1 v/v) and centrifuging the virus precipitate.
Properties of Particles
Purified preparations sediment as a major infective component, sometimes also with
dimers and trimers.
Sedimentation coefficient of monomers (s°20, w):
(Mosch et al., 1973);
190 S (M. Hollings & A. A. Brunt, unpublished data).
Isoelectric point: pH 4.64 for the yellow aucuba strain, and pH 4.50 for a green
mutant from this strain
(M. Hollings, unpublished data); both
values corrected for light-scattering.
Buoyant density: slightly higher for 18 strains of
tomato mosaic virus than for
tobacco mosaic virus,
(Mosch et al., 1973).
Electrophoretic mobility: -0.97 (µm/sec) (V/cm) at pH 7.0 and 0.075 ionic
strength (dahlemense strain)
(Kramer & Wittmann, 1958).
In 2% phosphotungstate, infective particles are straight tubules c.
300 x 18 nm,
and having a periodically deformed helical structure
(Caspar & Holmes, 1969
Particle CompositionNucleic acid
: RNA, single-stranded, about 5% of particle weight, probably
2 x 106
M. Wt. Nucleotide base ratios of 18 isolates of the
virus averaged: G 23: A28: C 19: U 30 moles %
(Mosch et al., 1973
Protein: In polyacrylamide gel electrophoresis, four strains of tomato
mosaic virus contained one polypeptide of estimated M. Wt (hydrated) c.
21,000 (M. Hollings & R. J. Barton, unpublished data). Similar amino acid
compositions were determined for 36 strains
(Wang & Knight, 1967;
Mosch et al., 1973;
Dawson et al., 1975).
The amino acid sequence of
the dahlemense strain
(Wittmann-Liebold & Wittmann, 1967)
contained 158 residues with a M. Wt of 17,640:
There are 30 amino acid exchanges from the type strain of
tobacco mosaic virus.
The methionine is in a different position from that in
ribgrass mosaic virus.
Relations with Cells and Tissues
The virus occurs in all tissues, including pollen and seeds, although probably
not in embryos
(Taylor et al., 1961
inclusions, recorded with different strains and in many natural and experimental hosts,
include: crystalline inclusions, amorphous bodies that become vacuolate
(Henderson Smith, 1930
hexagonal crystals, fine needles, fibrous spikes, spindle bodies, long
curved fibres, and amoeboid or X-bodies
(Kassanis & Sheffield, 1941
also angled layer aggregates
Aucuba mosaic strain has
been studied most, and amoeboid bodies formed with this strain
are now thought to differ from the X-bodies induced by
tobacco mosaic virus,
Most isolates from tomato are of tomato mosaic virus type;
tobacco mosaic virus
are seldom found
Komuro et al., 1966
for most of them compete poorly in tomato
(Komuro et al., 1966
Tomaru et al., 1970
and some (e.g. U2
tomato with difficulty or not at all
(Bald & Paulus, 1963
Tomato mosaic virus can be distinguished from other viruses affecting tomato as
follows. Tomato mosaic virus local lesions in Nicotiana glutinosa differ in size
and incubation period from those of
tomato spotted wilt and
tomato bushy stunt viruses.
tomato aspermy viruses
cause systemic mottle and distortion
in N. glutinosa and necrotic local lesions in Vigna sinensis.
Tomato black ring virus
induces systemic mottle in Phaseolus vulgaris
and Cucumis sativus;
tomato ringspot virus
gives symptoms similar to
those of tomato black ring virus in C. sativus but leaf-tip necrosis and
rugose mottle in P. vulgaris.
Potato virus Y
incites systemic vein clearing
mottle in N. glutinosa;
potato virus X
produces systemic chlorotic rings and
mottle in Datura stramonium.
Attempts to control tomato mosaic disease have been based on: (1)
production of virus-free (heat-treated) tomato seed; (2) milk or other sprays
applied to foliage to inhibit mechanical transmission of the virus
Hare & Lucas, 1959;
Denby & Wilks, 1963;
(3) Soil sterilization, which is usually inadequate to prevent subsequent
Broadbent & Winsor, 1964;
Broadbent et al., 1965;
van den Brock et al., 1967;
although all root infections do not necessarily progress to the shoots
(Komuro & Iwaki, 1969;
(4) Inoculation of tomato seedlings
with selected or induced mild strains of the virus
(Goto et al., 1966;
Boyle & Bergman, 1969;
Marrou & Migliori, 1971;
Fletcher & Rowe, 1975).
Mild strains may recover their
(Oshima & Goto, 1968),
however, or may change the relative
prevalence of strain types in subsequent tomato crops
(Fletcher & Butler, 1975).
(5) The use of genetically resistant tomato cvs
Alexander & Oakes, 1970;
Alexander & Farley, 1972;
Gates & McKeen, 1972);
single-gene resistance was soon overcome
Pelham et al., 1970),
but the three-gene resistant cvs Kirdford Cross and Pagham Cross
are still effective
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Tomato mosaic virus (dahlemense strain) in Craigella tomato seedling,
18 days after infection (left), showing local lesions in cotyledons, systemic
chlorotic mottle and severe stunting. Healthy plant (right). This also illustrates
the method of typing virus isolates by reactions in various isogenic lines of cv.
Craigella containing different combinations of resistance genes. This isolate has
infected and stunted plants containing gene Tm-1, and is thus in
Pelham group 1 (Pelham, 1972).
Symptoms of the aucuba mosaic strain in fruit of Moneymaker tomato,
visible as a light and dark green blotch-mottle.
Yellowish local lesions of a typical tomato mosaic virus isolate in Chenopodium
quinoa leaf 12 days after inoculation.
Relationships among some strains of the virus in immunodiffusion tests.
Central well contains antiserum to typical tomato mosaic strain AC; antigen wells
contain purified preparations of: O=Ohio III; T2 = Pelham strain
T2; M = typical tomato strain of Pelham type 0; T1.2 =
Pelham strain T1.2; D = dahlemense strain (a Pelham type 1 strain).
Dahlemense and T1.2 are closely related, whereas T2
and M share only some antigenic determinants; Ohio III is distantly related to the other
Necrotic local lesions of a typical tomato strain in Nicotiana tabacum
Dutch A necrotic selection, 9 days after inoculation.
Systemic veinal necrosis, mosaic mottle and leaf distortion in Dutch A
tobacco 2 weeks after infection with Ohio III strain.