Galinsoga mosaic virus
G. M. Behncken
Department of Primary Industry, Meiers Road, Indooroopilly, Queensland, 4068, Australia
R. I. B. Francki
Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia, 5064, Australia
A. J. Gibbs
Research School of Biological Sciences, Australian National University, Canberra, A.C.T., 2601, Australia
A virus with isometric particles c. 34 nm in diameter which contain
and sediment as a single component. Found only in Galinsoga parviflora (Compositae) in
Queensland, Australia. It is readily transmitted by inoculation with sap. In naturally infected
plants it is most concentrated in the roots and is transmitted through soil, apparently without the
aid of a vector.
The virus is found in nature only in potato weed, Galinsoga parviflora
(Compositae), in which it is usually restricted to the roots.
Of no known economic importance.
Host Range and Symptomatology
The virus has a wide experimental host range, infecting species
dicotyledonous families, but in most is confined to the inoculated leaves.
Readily transmitted by
inoculation with sap.
- Chenopodium amaranticolor. Small necrotic local lesions with chlorotic haloes
- C. quinoa. Necrotic local lesions; no systemic infection.
- Galinsoga parviflora. Chlorotic/necrotic local lesions;
systemic vein clearing (Fig.2)
followed by a severe chlorotic mosaic (Fig.3).
Systemically infected leaves later develop areas of necrosis and
become distorted, and the plant
becomes stunted (Fig.1).
- Phaseolus vulgaris cvs Bountiful, Pinto.
Small reddish-brown necrotic local lesions; no
systemic infection (Fig.5).
- Spinacia oleracea. Systemic chlorotic spots and vein necrosis. Leaves produced later are symptomless.
- Leaves of C. amaranticolor and P. vulgaris (cvs Hawkesbury Wonder, Canadian Wonder
or Royal Windsor) are suitable sources for virus purification.
- C. amaranticolor, C. quinoa or P. vulgaris are satisfactory local lesion hosts.
Transmission by Vectors
No vectors reported. The aphids Aphis gossypii
failed to transmit the virus
Transmission tests with the fungus
from roots of infected plants were also negative
Shukla et al., 1979
The roots of G. parviflora
plants became infected when grown (a) in
naturally infective soil, (b) in autoclaved potting mixture to which infective leaf
added or (c) in the same pot of autoclaved soil as a leaf-inoculated plant,
even when the tops of
the two plants were separated by a glass partition
(Shukla et al., 1979
suggest that the virus infects G. parviflora
roots without the aid of a vector.
Transmission through Seed
The virus was not transmitted in seed of G. parviflora
(Shukla et al., 1979
An antiserum with a titre of 1/1024 in gel diffusion tests was readily obtained
The virus shares properties with several viruses that have isometric particles
sedimenting as one component, but its particles are serologically
unrelated to those of any such
virus with which it has been compared.
In gel diffusion tests, galinsoga mosaic virus particles
and/or antiserum failed to react with those of 19 viruses from nine taxonomic groups
red clover necrotic mottle
southern bean mosaic
(sobemovirus group) and
tomato bushy stunt
Galinsoga mosaic virus particles also failed to
react with antisera to the following ungrouped viruses:
hibiscus chlorotic ringspot
velvet tobacco mottle
and uncharacterized viruses from Glycine
and Malvastrum coromandelianum
(G. M. Behncken, unpublished data).
Moreover its possession of a single genomic RNA species distinguishes galinsoga mosaic virus from
red clover necrotic mottle and velvet tobacco mottle viruses,
which have bipartite RNA genomes.
The particles of galinsoga mosaic virus are larger than those of
southern bean mosaic and
velvet tobacco mottle viruses, are less angular in outline, and show some surface structure.
mosaic virus shares most properties with tomato bushy stunt virus, which has particles of similar
size, appearance and composition but with a larger sedimentation coefficient (T. Hatta, R. I. B.
Francki & C. J. Grivell, unpublished data). Cells infected with either of
these viruses contain
multivesicular bodies which are of similar appearance but possibly develop from
(Russo & Martelli, 1972
Appiano, Pennazio & Redolfi, 1978
T. Hatta, R. I. B. Francki &
C. J. Grivell, unpublished data).
Stability in Sap
Sap from infected C. amaranticolor
leaves lost infectivity after 10 min
at 75-80°C, and when diluted to more than 10-6
. At 25°C sap
for 6 weeks.
Particles are readily purified from the inoculated leaves of either C.
or bean. Leaves are ground in 0.1 M phosphate buffer (pH 7.0)
sodium sulphite, the extract clarified by homogenizing with chloroform-butanol,
and the particles
concentrated and purified by differential centrifugation.
Properties of Particles
In sucrose density gradients and during analytical centrifugation,
the virus particles usually sediment as a single component.
Sedimentation coefficient (s20, w): 117.9±2.1 S; some preparations
also contain a minor 48 S component.
The 48 S component has a smaller absorbance ratio
(Skotnicki & Gibbs, 1981).
The particles are stable in 1 M CaCl2
Particles are isometric, c.
34 nm in diameter with a rounded profile
when negatively stained in uranyl acetate
They have a verrucose surface but the arrangement
of the subunits is not clear
(T. Hatta, R. I. B. Francki & C. J. Grivell, unpublished data).
Particle CompositionNucleic acid:
RNA, probably single-stranded, infective when deproteinized. A single RNA
species, of M. Wt c.
1.55 x 106
, estimated by polyacrylamide gel electrophoresis under non-denaturing
conditions. It constitutes about 22%
of the particle, and its percentage base composition is G 24.8±0.3; A 28.1±0.6;
C 21.8±1.0; U 25.3±0.7
(Skotnicki & Gibbs, 1981
Protein: Coat protein is a single species of M. Wt c. 36,400, estimated by
polyacrylamide gel electrophoresis. Percentage molar amino acid composition
(and best fitting
integral number of amino acids); ala 7.07 (26), arg 4.44 (16), asx 9.30 (34), cys 1.61 (6), glx
8.08 (29), gly 9.97 (36), his 2.14 (8), ile 2.99 (11), leu 8.75 (32), lys 4.70 (17), met 0 (0),
phe 9.30 (34), pro 4.47 (16), ser 8.89 (32), thr 9.09 (33), trp 0.81 (3), tyr 1.98 (7), val 6.42
(23); estimated total number of amino acids 363, M. Wt 39,505
(Skotnicki & Gibbs, 1981).
Relations with Cells and Tissues
Infected P. vulgaris
or G. parviflora
cells have particles throughout their cytoplasm and in some vacuoles,
but not in nuclei. In cell
sections the particle diameter is c.
contain numerous large
multivesicular bodies, which appear to be derived from mitochondria,
and the chloroplasts have some
marginal vesicles (T. Hatta, R. I. B. Francki & C. J. Grivell, unpublished data).
- Appiano, Pennazio & Redolfi, J. gen. Virol. 40: 277, 1978.
- Behncken, Aust. J. biol. Sci. 23: 497, 1970.
- Behncken, Aust. Pl. Path. Soc. Newsletter 1: 18, 1972.
- Hatta & Francki, J. Ultrastruct. Res. 74: 116, 1981.
- Russo & Martelli, Virology 49: 122, 1972.
- Shukla, Shanks, Teakle & Behncken, Aust. J. biol. Sci. 32: 267, 1979.
- Skotnicki &Gibbs, Australas. Pl. Path. 10: 27, 1981.
Symptoms of galinsoga mosaic in naturally infected Galinsoga parviflora (healthy
plant on right).
Systemic vein clearing in recently inoculated G. parviflora.
Severe systemic mosaic in chronically infected G. parviflora.
Local lesions in inoculated leaf of Chenopodium amaranticolor.
Local lesions in inoculated leaf of Phaseolus vulgaris.
Electron micrograph of particles negatively stained in uranyl acetate.
Bar represents 50 nm.
Electron micrograph of a thin section of an infected leaf cell of
P. vulgaris showing
the characteristic multivesicular bodies and vesicles associated with the
chloroplast membrane (arrows).
Insert shows vesicles at the outer membrane of a multivesicular body.
Sections were prepared from
tissues fixed with aldehyde and treated with ribonuclease to remove ribosomal RNA,
a process which
leaves the virus particles unaffected (Hatta & Francki, 1981). Bars represent 200 nm.