Cassia yellow blotch virus
J. L. Dale
Agricultural Research Laboratories, Department of Primary Industries, Indooroopilly, Queensland 4068, Australia
Described by Dale et al. (1984).
A virus with isometric particles c. 26 nm in diameter with four species of single-stranded
RNA, the three largest of which are required for infectivity. It is mechanically transmissible by
inoculation with sap but has a narrow experimental host range. Reported only from one western
district of Queensland, Australia.
Main DiseasesCassia pleurocarpa
(Leguminosae) is the only recorded natural host. The virus causes a
vivid yellow blotch symptom on the leaves
(Dale et al., 1984
Reported from only one western district of Queensland, Australia
(Dale et al., 1984
Host Range and Symptomatology
In Cassia pleurocarpa,
the only known natural host, the virus causes vivid yellow blotches
on the leaflets (Fig.1
The experimental host range (determined by inoculation with sap) is narrow:
the virus systemically infected only nine species from two families of the 44 species from seven
families tested (Dale et al., 1984
- Cassia occidentalis. Systemic chlorotic mottle develops 14-21 days after inoculation.
- Chenopodium amaranticolor. Fine discrete chlorotic local lesions develop 4-5 days after
inoculation (Fig.3). Does not become systemically infected.
- Nicotiana clevelandii. Systemic green mottle develops 10-16 days after inoculation
This is the only non-leguminous species that is reported to be systemically infected.
- Nicotiana clevelandii is suitable as a source of virus for purification. Cassia
occidentalis is suitable for maintaining cultures.
- Chenopodium amaranticolor is a suitable local lesion host.
No strains reported.
Transmission by Vectors
Transmission through Seed
The virus particles are very poorly immunogenic. In attempts to produce antisera by injecting
rabbits with either untreated or formaldehyde-treated virus particles, the best antiserum obtained
had a titre of only 1/8. In agarose gel double diffusion tests, this antiserum reacted with
formaldehyde-treated homologous virus particles to produce a single line of precipitation
(Dale et al., 1984
In its particle morphology and composition, cassia yellow blotch virus is more closely related
to the bromoviruses
) than to viruses of any other group. However, no serological
relationship has been found to
broad bean mottle
cowpea chlorotic mottle
In the amino acid composition of its coat protein, cassia yellow blotch virus is more closely related
to other bromoviruses than to cucumoviruses or
alfalfa mosaic virus
but less closely related to other
bromoviruses than they are to each other
(Dale et al., 1984
Stability in Sap
This virus can be purified by a method adapted from that of
Bancroft et al. (1967)
Extract sap from each 100 g N. clevelandii
leaf, harvested 10 to 14 days after inoculation,
in 200 ml 200 mM sodium acetate buffer, pH 4.8, containing 1 mM EDTA. Express the homogenate through
cheesecloth, incubate at 4°C for 4 h and then centrifuge at 8000 g
for 15 min.
Retain the supernatant fluid and add polyethylene glycol (M. Wt 6000) and sodium chloride to 10%
and 1% (w/v) respectively. Incubate at 4°C for 1 h and then centrifuge at 10,000 g
for 15 min. Resuspend the pellets in 100 mM sodium acetate buffer, pH 5.0, containing 1 mM EDTA and
centrifuge at 10,000 g
for 15 min. Further purify the virus from the resulting
supernatant fluid by two cycles of differential centrifugation (164,000 g
for 90 min
and 10,000 g
for 10 min), resuspending each time in 100 mM sodium acetate buffer, pH
5.0. This procedure results in yields of up to 400 mg virus/kg infected leaf tissue.
Properties of Particles
At pH 5.0, the virus particles sediment as a single component whereas at pH 7.0 they sediment as
three components, one slightly slower than the single component at pH 5.0 and two considerably more
). This probably results from the swelling of the particles at pH 7.0.
Sedimentation coefficient at pH 5.0 (s°20, w): 85.1 S.
Isoelectric point: pH 3.6.
The particles are rounded to slightly angular and have a diameter of 25-27 nm
). In uranyl
acetate or sodium phosphotungstate, the particles may collapse on the grid to produce a central cavity
that contains a pool of stain.
Particle CompositionNucleic acid:
RNA, single-stranded. Under non-denaturing conditions
(Peacock & Dingman, 1968
the RNA migrated as four major bands
) with apparent M. Wt (x 10-6
) of 1.10
(RNA-1), 0.96 (RNA-2), 0.78 (RNA-3) and 0.31 (RNA-4). Only the three largest RNA molecules are
required for infectivity. The percentage base composition of the RNA was guanine 24.4, adenine 24.9,
cytosine 22.2 and uracil 28.5 (Dale et al., 1984
Protein: A single protein species which under denaturing conditions
(Laemmli, 1970) has an
apparent M. Wt of 20,800 ± 1%. Amino acid composition indicates that the coat protein contains 196
amino acid residues (Dale et al., 1984).
Relations with Cells and Tissues
The virus is difficult to confuse with others. It has been found only in western Queensland in an
Australian native legume, Cassia pleurocarpa.
No other viruses have been reported to infect
this species, but
bean yellow mosaic virus
has been recorded in a number of other
spp. in Australia.
- Bancroft, Hills & Markham, Virology 32: 354, 1967.
- Dale, Gibbs & Behncken, J. gen. Virol. 65: 281, 1984.
- Laemmli, Nature, Lond. 277: 680, 1970.
- Lane, in Handbook of Plant Virus Infections and Comparative Diagnosis, p. 333, ed. E. Kurstak, 943 pp., New York: Elsevier/North Holland, 1981.
- Peacock & Dingman, Biochemistry 7: 668, 1968.
Symptoms in leaflets of naturally infected Cassia pleurocarpa.
Systemically infected leaf of Nicotiana clevelandii.
Inoculated leaf of Chenopodium amaranticolor.
Particles in a purified preparation negatively stained with uranyl acetate. Bar marker
represents 100 nm.
Sucrose gradient separation of virus particles after incubation at different pH values.
Purified preparations were incubated in and centrifuged through either (a) 25 mM sodium acetate,
pH 5.0, or (b) 25 mM potassium phosphate, pH 7.0.
Densitometer trace at 580 nm of RNA components after electrophoresis in a 2.5%
polyacrylamide gel and staining with toluidine blue.