Cassava Ivorian bacilliform virus
Laboratoire de Phytovirologie des Regions Chaudes, CIRAD, ORSTOM, BP5035, 34032 Montpellier, France
B. D. Harrison
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
Aiton et al. (1988)
Fargette et al. (1991)
A virus with bacilliform particles c
. 18 nm in diameter and predominant
lengths of 42, 49 and 76 nm. Transmissible by inoculation with sap and having
affinities to the genus Alfamovirus
. Reported from cassava in Côte
Found naturally in cassava (Manihot esculenta
: Euphorbiaceae) plants
co-infected with African cassava mosaic begomovirus
Its effects on
begomovirus-free cassava are unclear and it may be of only trivial economic
importance. Probably maintained in cassava by vegetative propagation of
The type isolate was originally obtained from a cassava plant collected at
Touresso, Côte d'Ivoire. However, the occurrence of CIBV at several other sites
in north western Côte d'Ivoire suggests that it is more than a casual pathogen of
Host Range and Symptomatology
Only known natural host is cassava but the virus was transmitted experimentally
to 12 species in five other families. All were infected systemically but several
remained symptomless. Nineteen other species in eight plant families were not
- Chenopodium amaranticolor. Inoculated leaves symptomless. Slight
distortion and stunting of systemically infected tip leaves.
- C. murale. Necrotic lesions developed in inoculated leaves after 2-3
appeared in tip leaves about 5 days
- C. quinoa. Faint chlorotic lesions, sometimes with some necrosis, in
Systemic shoot necrosis developed after 5-7 days
eventually spreading to kill some plants.
- Tetragonia expansa. Necrotic local lesions and symptomless
- Nicotiana benthamiana, N. clevelandii and Phaseolus vulgaris
become infected systemically but develop few or no symptoms.
- C. quinoa is suitable for maintaining isolates and is a good source of
virus for purification.
- C. murale is a useful local lesion assay host.
Isolates differ in virulence. Isolate F143 caused symptomless systemic infection
instead of systemic necrosis in C. quinoa
and chlorotic instead of necrotic
local lesions in C. murale.
Transmission by Vectors
No vector is known. CIBV was not transmitted by Myzus persicae
an acquisition access period of <2 h.
Transmission through Seed
Poorly immunogenic. Antiserum from a rabbit given nine intramuscular
injections had a titre of only 1/64 in double diffusion tests in agarose gel. In
DAS-ELISA, purified virus particles were detected at concentrations down to
about 6 ng/ml. With crude sap of systemically infected C. quinoa
detection end point was about 10-4
. In immunosorbent electron
microscopy (ISEM), the number of virus particles on grids was more than 50-fold
greater than on uncoated grids.
In ISEM no increase in particle numbers was observed when grids were coated
with antiserum to
prunus necrotic ringspot
olive latent 2 viruses.
Little if any reaction occurred when CIBV
antibodies were used in DAS-ELISA in attempts to detect alfalfa mosaic virus.
CIBV appears to be a distinct virus which nevertheless has strong affinities with
alfalfa mosaic virus.
Stability in SapC. quinoa
leaf extracts in 50 mM borate buffer, pH 8.5, were infective
after dilution to 10-2
but not at 10-3
, and after
heating for 10 min at 50°C but not at 55°C. In N. benthamiana
CIBV concentration seemed unaffected by co-infection with
African cassava mosaic begomovirus
Extract systemically infected C. quinoa
leaves, harvested 5-7 days after
plants are inoculated, in 5 mM borate buffer (4 ml/g leaf) at pH 8.5, using a
Waring blendor. Re-extract fibre. Emulsify combined extracts with chloroform,
separate aqueous phase by centrifugation (10,000 g
, 10 min)
and add polyethylene glycol (M. Wt 6000) and sodium chloride to 60 g/l and 0.2
M, respectively. Collect precipitate by centrifugation (10,000 g
10 min), resuspend in 0.1 M phosphate buffer, pH 5.8, containing 4 mM EDTA (1
ml buffer/5 g initial tissue), and further purify and concentrate virus particles by
one cycle of differential centrifugation (10,000 g
, 10 min;
, 45 min), followed by resuspension, sucrose density
gradient centrifugation (250,000 g
, for 60 min in Beckman
SW50.1 rotor), and then ultracentrifugation of the virus-containing fractions.
Resuspend the final pellets in 1 mM Tris-HCl buffer, pH 7.0, containing 2 mM
Properties of Particles
Particles are bacilliform, 18 nm wide and about 42, 49 or 76 nm long
Three corresponding sedimenting components are resolved by sucrose density
A260/A280 = 1.7 ± 0.05
(suggestive of about 25% nucleic acid).
1.30 ± 0.05.
CIBV particles stained with uranyl acetate
have a structure resembling
that of particles of
alfalfa mosaic virus
in which the stain penetrates eyes at
regular intervals along the length of appropriately orientated particles (see
Johnson & Argos, 1985
In that virus, the tubular part of the particle is made up
of interlocking hexagonal arrays of protein subunits, with holes penetrated by
stain at the 6-fold vertices. This structure repeats at 8 nm intervals; the rounded
ends of the particles are thought to consist of the two halves of an icosahedron.
The appearance of CIBV particles, notably the occurrence of eyes and the
end-on view, is compatible with a similar model. Assuming a longitudinal repeat
of the structure of CIBV particles every 8 nm, particle lengths of 42, 50 and 74
nm are possible, close to the observed values of 42, 49 and 76 nm.
Particle CompositionNucleic acid:
Three RNA components were detected by electrophoresis
in agarose gel. Assuming they are single-stranded, they have Mr
) of 0.9, 1.0 and 1.3.
Protein: One particle protein of Mr c. 22,000.
Relations with Cells and Tissues
Ecology and Control
Vegetative planting material should not be moved from Côte d'Ivoire to other
countries unless it is apparently free of CIBV after suitable tests, e.g. mechanical
inoculation of leaf extracts to C. murale
, DAS-ELISA with CIBV antibodies
(Fargette et al., 1991
Frison & Feliu, 1991
Except where indicated, the above data were obtained by
Fargette et al. (1991)
alfalfa mosaic virus
Jaspars & Bos, 1980)
shape, diameter and, probably, structure of its particles. However, only three
predominant lengths of particle and only three RNA species were found, whereas
alfalfa mosaic virus has four of each. CIBV resembles alfalfa mosaic virus in
infecting species in the Fabaceae and Solanaceae, but its host range is more
limited: of the 19 species not infected by CIBV, 13 (six plant families) are hosts
of alfalfa mosaic virus. Also, the concentration of CIBV in sap is 10- to 100-fold
less than that of alfalfa mosaic virus, no relationship between the two viruses
could be detected by ISEM and only a very distant, and dubious, relationship
could be found by DAS-ELISA. Evidently CIBV is a distinct virus. It is
considered to be a tentative member of the genus Alfamovirus.
- Aiton, Lennon, Roberts & Harrison, Abstr. 5th Int. Congr. Pl. Path. Kyoto, p.43, 1988.
- Fargette, Roberts & Harrison, Ann. appl. Biol. 119: 303, 1991.
- Frison & Feliu (eds), FAO/IBPGR Technical Guidelines for the Safe Movement of Cassava Germplasm, 47 pp, FAO/IBPGR, Rome, 1991.
- Hull, Adv. Virus Res. 15: 335, 1969.
- Jaspars & Bos, CMI/AAB Descr. Pl. Viruses 229, 7 pp., 1980.
- Johnson & Argos, In The Plant Viruses. 1. Polyhedral Virions with Tripartite Genomes, p. 19, ed. R. I. B. Francki, Plenum Press, New York,1985.
Necrotic lesions in inoculated leaf of C. murale.
Systemic necrosis in C. murale.
Necrotic spots in inoculated leaf of C. quinoa.
Systemic stunt and necrosis in C. quinoa.
Purified particles of CIBV (18 nm wide) negatively stained with
Purified particles of CIBV negatively stained with uranyl acetate.