Details of DPV and References
DPV NO: 357 September 1998
Species: Cassava American latent virus | Acronym: CsALV
Cassava American latent virus
B. Walter INRA, 28 rue de Herrlisheim, F 68021 Colmar, France
- Main Diseases
- Geographical Distribution
- Host Range and Symptomatology
- Transmission by Vectors
- Transmission through Seed
- Transmission by Grafting
- Transmission by Dodder
- Nucleic Acid Hybridization
- Stability in Sap
- Properties of Particles
- Particle Structure
- Particle Composition
- Properties of Infective Nucleic Acid
- Molecular Structure
- Genome Properties
- Relations with Cells and Tissues
- Ecology and Control
First described by
Walter et al. (1989) from Manihot
esculenta cultivars originating from Brazil and Guayana.
A virus with isometric particles c. 28 nm in diameter sedimenting as three components. The genome comprises two RNA species of Mr c. 2.54 x 106 (RNA-1) and 1.44 x 106 (RNA-2). Host range limited to species in the families Chenopodiaceae, Euphorbiaceae and Solanaceae.
Cassava American latent virus (CsALV) was detected during a survey of cassava (Manihot esculenta) cultivars originating from South America (Walter et al., 1989). It was found in plants that were also infected by the potexvirus cassava common mosaic virus and showed symptoms of mild mosaic. Preparations of purified CsALV back inoculated on to cassava seedlings induced no visible symptoms, though the virus was detected in systemically infected leaves by ELISA 9 weeks after inoculation.
Reported only from Brazil and Guyana. No further information.
Host Range and Symptomatology
The virus is mechanically transmissible to species of Chenopodiaceae, Euphorbiaceae and
(Walter et al., 1989).
- Diagnostic species
Chenopodium album and C. amaranticolor: local chlorotic lesions becoming necrotic (Fig. 1).
Nicotiana benthamiana: diffuse chlorotic areas both on inoculated and on systemically infected leaves followed by discrete flecking on the whole plant (Fig. 2).
Tetragonia expansa (Aizoaceae), Gomphrena globosa (Amaranthaceae), Euphorbia prunifolia (Euphorbiaceae) and Nicotiana tabacum (Solanaceae) are useful non-host species.
- Assay species
- Propagation species
Nicotiana benthamiana and N. clevelandii.
Transmission by Vectors
Transmission through Seed
Strongly immunogenic. Rabbit polyclonal antiserum has been used in gel double-diffusion (titre 1/2048), ELISA and ISEM. The virus was detectable by double antibody sandwich (DAS)-ELISA in high dilutions (10-3 to 10-4) in cassava and N. benthamiana leaf extracts (Walter et al., 1989).
On the basis of its particle properties, the virus is placed in the genus Nepovirus (Mayo & Robinson, 1996). No serological relationship was detected to another nepovirus from cassava, cassava green mottle virus, nor to seven other nepoviruses: arabis mosaic, grapevine chrome mosaic, grapevine fanleaf, raspberry ringspot (serotypes E and S), strawberry latent ringspot, tomato black ring (serotypes G and S) and tomato ringspot (Walter et al., 1989).
Stability in Sap
In sap of N. benthamiana the thermal inactivation point (10 min) is between 70 and 72°C and the dilution end-point is between 10-3 and 10-4 (Walter et al., 1989).
Virus purification is possible from leaves of N.
benthamiana or N. clevelandii ground in 0.05 M
buffer, pH 7.5 (2 ml/1 g leaves). After clarification with butan-1-ol,
precipitation with 10% polyethylene glycol (PEG) and differential
centrifugation, centrifuge the virus through a 20% (w/v) sucrose cushion
and fractionate in a 10-50% sucrose gradient
(Walter et al., 1989).
To purify the virus directly from cassava, grind leaves in phosphate buffer containing 2% polyvinylpyrrolidone (2 ml/1 g leaves). After addition of 2% Triton X-100 and emulsifying with 1/10 volume chloroform, process the aqueous phase as above (PEG, sucrose cushion and sucrose gradient).
Properties of Particles
B component particles have a buoyant density of 1.5 g cm-3 in CsCl.
Three virus-associated peaks (T, M and B components) are observed in sucrose gradients. When observed in electron microscopy, M and B fractions contain only isometric particles c. 28 nm in diameter appearing mostly unpenetrated by negative stain (Fig. 3); the T fraction contains particles of the same size penetrated by the stain.
Nucleic acid: Two RNA molecules of Mr 2.54 x
106 (RNA-1) and 1.44 x 106 (RNA-2).
B component particles contain both RNA molecules, whereas M component
particles contain only RNA-2; T component particles contain no RNA.
Protein: A single protein, of Mr 57,000 (Walter et al., 1989).
Many of the properties of CsALV are typical of nepoviruses. It may belong to those nepoviruses having a single major coat protein and a heterogeneous B component with either one molecule of RNA-1 or two molecules of RNA-2, and an RNA-2 of Mr 1.3-1.5 x 106 (Mayo & Robinson, 1996).
References list for DPV: Cassava American latent virus (357)
- Mayo & Robinson, in The Plant Viruses, Vol. 5, p. 139, ed. B.D. Harrison & A.F. Murant, 362 pp., New York: Plenum Press, 1996.
- Walter, Ladeveze, Etienne & Fuchs, Ann. appl. Biol. 115: 279, 1989.