Poplar mosaic virus
P. G. Biddle
Commonwealth Forestry Institute, Oxford, England
T. W. Tinsley
Commonwealth Forestry Institute, Oxford, England
- Described by Atanasoff (1935) and Berg (1964).
- Canadian poplar mosaic (Rev. appl. Mycol. 14: 462)
- A virus with flexuous filamentous particles c. 675 nm long. Only known
natural host is poplar, in which it is common and can cause severe growth losses.
Many other plant species can be infected by inoculation of sap. There is no known
vector, but it is widely disseminated in infected cuttings.
Causes a mosaic (Fig.1
) or diffuse spotting (Fig.2
) in mature leaves of most
poplar clones, but some clones react more severely, with necrosis of veins and leaf
stalks, swellings round the bases of the petioles, and small lesions and splits on
the stem. Growth of infected trees, particularly of those showing more severe leaf
symptoms, is reduced, and there are also effects on the specific gravity and
strength of wood from infected trees (Biddle & Tinsley, 1971b
Throughout the geographical range of susceptible poplar species and clones.
Host Range and Symptomatology
Natural hosts are poplars in the Sections Aigeiros and Tacamahaca, but species
in 20 dicotyledonous families can be infected by inoculation of sap (Schmelzer, 1966
- Diagnostic species
- Nicotiana megalosiphon (Fig.3) and N. glutinosa. Faint chlorotic
local lesions after 10 days, followed by systemic vein-clearing and leaf-curling.
Veins occasionally become necrotic.
- Lavatera trimestris. Small necrotic local lesions, followed by systemic
vein-clearing and vein-necrosis.
- Vigna sinensis (cowpea). Red local lesions develop after 7 days, tending
to spread along the veins they contact (Fig.4); systemic vein-clearing after about
20 days followed by vein-reddening and leaf deformation.
- Propagation species
- Nicotiana megalosiphon is the most suitable species for maintaining the
virus and providing material for purification.
- Assay species
- Vigna sinensis sometimes produces countable lesions, but is not a reliable
Most isolates seem identical, although Blattný (1965)
distinguished a more severe strain in Populus
Transmission by Vectors
A low rate of natural transmission has been noted in the field, but no vector
has been satisfactorily implicated. Boyer (1962)
claimed that the aphid
transmits the virus, but other workers have been
unable to confirm this. Circumstantial evidence suggests that the virus may spread
through root grafts, but from experiments with radioactive tracers, the number of
root grafts seems too few to account for the rate of virus spread (P. G. Biddle,
Transmission through Seed
Transmission by DodderCuscuta californica
and C. subinclusa
failed to transmit the
virus from Nicotiana glutinosa
to N. megalosiphon
The virus is moderately immunogenic. Antisera with titres of 1/2048 are
commonly obtained. Gel-diffusion tests are unsatisfactory, but microprecipitation
tests give good results (Berg, 1964
The morphology of its particles and their stability and sedimentation
coefficient suggest that poplar mosaic virus is a member of the potato virus S
group of viruses (Brandes & Wetter, 1959
). However, no interaction was detected
between poplar mosaic virus and antisera against viruses of this group such as pea
, red clover vein mosaic
, carnation latent
, potato S, potato M
and freesia mosaic viruses, or against other viruses with
filamentous particles such as potato X
, potato Y
, bean yellow mosaic
, iris mosaic
and tulip breaking
viruses (Berg, 1964
Stability in Sap
In Nicotiana megalosiphon
sap, the thermal inactivation point is about
dilution end-point about 10-5
, and infectivity persists in vitro
for 2 days at room temperature and for
6 days at 4°C (Schmelzer, 1966
). An isolate studied by Biddle & Tinsley
) was somewhat less
stable and less concentrated in sap. Infectivity in poplar extracts is greatly
increased by adding
0.1 g of insoluble polyvinyl pyrrolidone to each 1 ml of extraction medium.
Freeze infected Nicotiana megalosiphon
leaves and triturate in buffer
(0.05 M Na2
, 1 mM di-sodium ethylene
diaminetetraacetate, 0.2 M Na2
; pH 7.5). Heat the extract
to 50°C, centrifuge at low speed, precipitate the virus by adding ammonium
sulphate to 30-45% saturation, and resuspend in buffer. Further purify by
centrifuging in sucrose density gradients or by clarifying with chloroform followed
by molecular exclusion chromatography in columns of 2% agarose beads. The virus is
liable to aggregate, and virus sedimented in the ultracentrifuge is difficult to
resuspend (Biddle & Tinsley, 1971a
Properties of Particles
Sedimentation coefficient (s20,w
) at infinite dilution:
165 S (Berg, 1964
Slightly flexuous filamentous particles c.
675 nm long (Fig.5
Relations with Cells and Tissues
All tissues in poplar are infected, including cambium, phloem and xylem
). Metabolic disturbances to the differentiating xylem result in reduced
growth and abnormalities of the wood structure (Biddle & Tinsley, 1971b
This is the only known virus of poplar. Its widespread occurrence undoubtedly
arises from dissemination of infected poplar cuttings. The use of healthy plants
for propagation, and rogueing of infected plants. effectively controls the
disease, because natural transmission appears to be rare.
- Atanasoff, Phytopath. Z. 8: 197, 1935.
- Berg, Meded. LandbHoogesch. Wageningen 64: 11, 1964.
- Biddle & Tinsley, New Phytol. 70: 61, 1971a.
- Biddle & Tinsley, New Phytol. 70: 67,1971b.
- Blattný, Lesn. Cas. 11: 637, 1965.
- Boyer, Can. J. Bot. 40: 1237, 1962.
- Brandes & Wetter, Virology 8: 99, 1959.
- Schmelzer, Phytopath. Z. 55: 317, 1966.
Leaf of Populus x euramericana cv. Robusta showing mosaic.
Chlorotic spots in Populus x euramericana cv. Regenerata.
Systemic symptoms in Nicotania megalosiphon.
Local lesions in Vigna sinensis.
Virus particles from clarified sap in uranyl acetate. Bar represents