Tobacco necrosis virus
Rothamsted Experimental Station, Harpenden, Hertfordshire, England
Smith & Bald (1935),
Babos & Kassanis (1963a).
- Tulip Augusta disease virus (Rev. appl. Mycol. 29: 215)
An RNA-containing virus with isometric particles about 26 nm in diameter. Readily
transmitted by mechanical inoculation to a wide range of plants, but usually does not
infect them systemically. Soil-borne, transmitted by zoospores of the chytrid fungus
Olpidium brassicae. Distribution world-wide.
Tulip necrosis (Augusta disease)
bean stipple streak
(van der Want, 1948
ABC disease of potato tubers
and one form of cucumber necrosis
(van Koot & van Dorst, 1955
from pear trees showing ring pattern and bark split symptoms
(Kegler et al., 1969
(Cesati & van Regenmortel, 1969
and from citrus
(Bové, personal communication).
World-wide, common in irrigated fields, also in
unsterilized soil in glasshouses.
Host Range and Symptomatology
Transmitted experimentally to at least 88
species in 37 dicotyledonous and monocotyledonous families
causing necrotic lesions and rarely infecting systemically. Has been obtained from
the naturally infected roots of many species of plants, but infects few species
- Phaseolus vulgaris cv. The Prince (French bean). Symptoms depend on virus
strain. Strains of group D (see Relationships) give discrete local lesions
whereas those of group A give local lesions that spread along the minor veins
Some strains do not infect. Only the stipple streak strain infects systemically.
are present the concentration of tobacco necrosis virus
and the size of the lesions are both decreased.
- Nicotiana tabacum (tobacco)
Phaseolus vulgaris and, for
some strains, Nicotiana clevelandii. As the virus causes only local lesions
every leaf must be inoculated, with added abrasive, to obtain good yields of virus.
- Phaseolus vulgaris or, for some strains, Chenopodium amaranticolor,
are good hosts for local lesion assays. In tests for transmission of virus to roots
by vectors, Mung bean (Phaseolus aureus), which gives local lesions in roots,
lettuce (Lactuca sativa) and tobacco are useful.
Many strains have been distinguished by their symptomatology and
host range, serological specificity and ability to activate different
strains (see Relationships). They include strains A, B, C, D, E and S
(Babos & Kassanis, 1963a
strain C = cucumber necrosis strain of
van Koot & van Dorst (1955)
strain S = stipple streak strain of
van der Want (1948)
AC36, AC38, AC39 and AC43
(Uyemoto, Grogan & Wakeman, 1968
and the Urbana
(Lesnaw & Reichmann, 1969
Variants that seem to exist as free nucleic acid and are transmissible only when
phenol or bentonite are used to prepare inocula, have been found
(Kassanis & Welkie, 1963).
Transmission by Vectors
The virus is transmitted by zoospores of the
root-infecting chytrid fungus Olpidium brassicae
Teakle & Gold, 1963
Kassanis & Macfarlane, 1964
The virus is quickly
acquired by zoospores added to virus suspensions and enters the root at the same
time as the fungus. Transmission depends on having a suitable combination of virus
strain, fungus race and host species
(Kassanis & Macfarlane, 1965
does not survive in the resting spore of the fungus.
Transmission through Seed
Transmission by Dodder
Moderately immunogenic. Antisera collected 10 days after a single
intravenous injection of virus (2 mg) are more specific than sera collected after a
long immunization procedure that includes an intramuscular injection. The virus
reacts well in tube tests in which it gives a granular precipitate, and in gel-diffusion
tests in which it gives a single band of precipitate.
Tobacco necrosis virus is serologically unrelated to
which multiplies only in plants that are also infected with tobacco necrosis
(Kassanis & Nixon, 1961
Strains of tobacco necrosis virus fall into two
serological groups or serotypes
(Babos & Kassanis, 1963a
contains strains A, B, C and S; Group D contains strains D, E, AC43, AC36, and the
strains obtained from pear, grapevine and citrus. The strains are most easily grouped
using the specific antisera obtained after a single injection of immunogen
(Kassanis & Phillips, 1970
Groups based on serological tests do not coincide with groups based on symptoms,
nor with those based on the ability of strains to support the growth of satellite
virus strains, for some strains of group D will only support satellite virus strains
SV1 and SV2, whereas others will only support strain
SVc; all strains of group A support SV1 and SV2
but not SVc
(Kassanis & Phillips, 1970).
The cucumber necrosis strain is not to be confused with the
cucumber necrosis virus
this and other similar viruses seem unrelated to tobacco
(Dias & Douane, 1968).
Moreover, cucumber necrosis virus is
transmitted by the zoospores of Olpidium cucurbitacearum, but not by those
of O. brassicae
Stability in Sap
In sap from infected tobacco the thermal inactivation point
is between 85°C and 95°C depending on the virus strain. At 20°C the sap
remains infective for many days, and at -20°C for several years. The kinetics of
heat inactivation were studied by
Babos & Kassanis (1963b)
The following procedure is useful with most strains of the
virus. Frozen leaves or leaf pulp are thawed and triturated in a blender with water.
After low speed centrifugation, virus is precipitated from clarified sap by adding
ammonium sulphate (0.25 g/ml), resuspending the precipitate in a sufficient volume
of water, sedimenting the virus in the ultracentrifuge and then resuspending the
pellet in water. Precipitation and sedimentation are repeated until the preparation
is clear (usually three cycles), taking care to ensure that most of the virus has
been recovered from the pellets. Preparations can be further fractionated by
centrifuging in sucrose density gradients.
Properties of Particles
Purified preparations contain one type of particle.
Sedimentation coefficient (s20, w) at infinite dilution: c.
118 S, though smaller and larger values have been reported.
Molecular weight (daltons): c. 7 x 106 (calculated from the
RNA content and size).
Isoelectric point: c. pH 4.5; strain B precipitates at pH 4.5 in the
presence of salts.
Electrophoretic mobility: -7.4 x 10-5 and -3 x 10-5
cm2 sec-1 volt-1 respectively for strains B and
A in 0.066 M phosphate buffer, pH 7.0.
Absorbance at 260 nm (1 mg/ml, 1 cm light path): 5.0-5.5.
(Cesati & van Regenmortel, 1969).
Buoyant density in CsCl: 1.399
(Cesati & van Regenmortel, 1969).
All strains of the virus, except strain B, readily crystallize.
Particles are isometric, about 26 nm in diameter
They may be negatively stained with acid phosphotungstate except for strain B, which
is degraded in the stain unless previously treated with 2% formaldehyde for 30 min.
Details of structure not known.
Probably single-stranded; molecular weight 1.3-1.6 x 106
constitutes about 19% of the particle weight. The reported nucleotide compositions
(Uyemoto & Grogan, 1969
Lesnaw & Reichmann, 1969
C22-23; U24-27 (moles %). s20, w
in 0.1 M NaCl: 27 S.
Protein: About 80% of particle weight. Probably only one kind of protein
in particle. Molecular weight variously reported as 22,600 (197 residues;
Uyemoto & Grogan, 1969)
and 33,500 (312 residues;
Lesnaw & Reichmann, 1969).
amino acid compositions reported by these authors also differ greatly.
Relations with Cells and Tissues
Virus particles occur in cytoplasm
(Kassanis, Vince & Woods, 1970
This virus is of academic interest because of its mode of transmission
by Olpidium brassicae
and its relations with
on it for multiplication.
- Babos & Kassanis, J. gen. Microbiol. 32: 135, 1963a.
- Babos & Kassanis, Virology 20: 490, 1963b.
- Bawden, Brit. J. exp. Path. 22: 59, 1941.
- Cesati & van Regenmortel, Phytopath. Z. 64: 363, 1969.
- Dias, Proc. Can. phytopath. Soc. 36: 13, 1969.
- Dias & Douane, Can. J. Bot. 46: 47, 1968.
- Kassanis, Ann. appl. Biol. 36: 14, 1949.
- Kassanis, Annls Inst. phytopath. Benaki 6: 7, 1964.
- Kassanis & Macfarlane, J. gen. Microbiol. 36: 79, 1964.
- Kassanis & Macfarlane, Virology 26: 603, 1965.
- Kassanis & Nixon, J. gen. Microbiol. 25: 459, 1961.
- Kassanis & Phillips, J. gen. Virol. 9: 119, 1970.
- Kassanis, Vince & Woods, J. gen. Virol. 7: 143, 1970.
- Kassanis & Welkie, Virology 21: 540, 1963.
- Kegler, Prohl, Schmidt & Opel, Phytopath. Z. 65: 21, 1969.
- Lesnaw & Reichmann,Virology 39: 729, 1969.
- McKeen, Can. J. Bot. 37: 913, 1959.
- Noordam, Tijdschr. PlZiekt. 63: 237, 1957.
- Price, Am. J. Bot. 27: 530, 1940.
- Smith & Bald, Parasitology 27: 231, 1935.
- Teakle, Virology 18: 224, 1962.
- Teakle & Gold, Virology 19: 310, 1963.
- Uyemoto & Grogan, Virology 39: 79, 1969.
- Uyemoto, Grogan & Wakeman, Virology 34: 410, 1968.
- van der Want, Tijdschr. PlZiekt. 54: 85, 1948.
- van Koot & van Dorst, Tijdschr. PlZiekt. 61: 163, 1955.
Part of a leaf of Phaseolus vulgaris inoculated with strain
Part of a leaf of Phaseolus vulgaris inoculated with strain E.
Part of a leaf of Phaseolus vulgaris inoculated with strain D.
Lesions of strain A in an inoculated leaf of Nicotiana tabacum.
A tulip plant with tulip necrosis (Augusta disease).
A bean plant infected with stipple streak strain.
Virus particles from a purified preparation stained with phosphotungstate.
Bar represents 100 nm.
Zoosporangia of Olpidium brassicae in a root cell. Bar represents
Zoospores of O. brassicae. Bar represents 20 µm.