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Descriptions and Lists from the VIDE Database

Cassava African mosaic bigeminivirus

Index

• Nomenclature
• Host range, transmission and symptoms
• Physical and biochemical properties
• Taxonomy and relationships
• Comments and References

Data collated by C. Büchen-Osmond, 1987. Revised by B.D. Harrison, 1989.

Nomenclature

Synonyms

cassava latent virus, cassava mosaic virus, cassava African mosaic virus.

Acronym

ACMV

Strains

type strain isolate 844 (Bock et al., 1978); Kenya coast (C) strain (Bock et al., 1981), Angola defective isolates (Sequeira and Harrison, 1982).

ICTV decimal code

29.0.3.0.004

Host range and symptoms

Natural host range and symptoms

Symptoms persist and vary cyclically over a few weeks.
• Manihot esculenta, Jatropha multifida - severe mosaic.
• Hewittia sublobata - mosaic (probably the natural host of the Kenya coast strain; Bock et al., 1981).
• Laportea (=Fluerya) aestuans - bright chlorosis (possibly the natural host in Nigeria; Anon., 1979).
• Manihot glaziovii - mosaic.

Transmission

Transmitted by a vector; an insect; Bemisia tabaci (Chant, 1958; Dubern, 1979); Aleyrodidae. Transmitted in a persistent manner. Virus retained when the vector moults; not transmitted congenitally to the progeny of the vector (Dubern, 1979); transmitted by mechanical inoculation (with difficulty to cassava (Bock and Woods, 1983) but more readily to Nicotiana benthamiana); transmitted by grafting; not transmitted by seed.

Ecology and control

Studies reported by Bock and Guthrie (1982); Bock (1984); Robertson (1984). Incidence often exceeds 80%, but only a quarter of the cuttings of infected susceptible cassava cultivars yield healthy plants (Bock, 1983). Virus-free cassava plants can be produced by heat treatment and meristem-tip culture. Some cassava genotypes resist infection. Two methods of control are advocated; in Kenya (Bock and Guthrie, 1982; Bock, 1983) and the Ivory Coast (Fargette et al., 1985), virus-free planting material of cultivars with moderate resistance to infection is used, whereas in Nigeria cultivars with superior resistance to, and tolerance of, infection are favoured (Hahn et al., 1980).

Geographical distribution

Spreads in the African region; Angola, Kenya, Nigeria, and the Seychelles.

Experimental host range

Few (<3) families susceptible. Experimentally infected plants mostly show chlorotic local lesions, systemic mosaic, leaf curling.

Diagnostically susceptible host species and symptoms

• Manihot esculenta - bright mosaic 3-5 weeks after inoculation by whitefly or by grafting. Leaves with symptoms may alternate with leaves showing few or no symptoms.
• Nicotiana benthamiana - diffuse chlorotic lesions then systemic leaf curling, malformation and blotching.
• Nicotiana clevelandii - the type strain may induce chlorotic local lesions then severe malformation, and irregular yellow veinbanding and blotching. The Kenya coast strain is milder and less readily transmitted.
• Datura stramonium - type strain induces chlorotic and necrotic local lesions then systemic veinbanding, leaf curling and malformation.

Diagnostically insusceptible host species

Cucurbita pepo, Chenopodium amaranticolor, Gomphrena globosa, Phaseolus vulgaris.

Maintenance and propagation hosts

Manihot esculenta, Nicotiana benthamiana.

Assay hosts (Local lesions or Whole plants)

Datura stramonium (L) for type strain; Nicotiana benthamiana (W) for Kenya coast strain.

Susceptible host species

• Datura ferox
• Datura stramonium
• Hewittia sublobata
• Jatropha multifida
• Laportea aestuans
• Manihot esculenta
• Manihot glaziovii
• Nicandra physalodes
• Nicotiana benthamiana
• Nicotiana clevelandii
• Nicotiana debneyi
• Nicotiana glutinosa
• Nicotiana rustica
• Nicotiana tabacum
• Solanum nigrum

Insusceptible host species

• Atriplex hortensis
• Beta vulgaris
• Capsicum frutescens
• Chenopodium amaranticolor
• Chenopodium quinoa
• Citrullus lanatus
• Cucumis melo
• Cucumis sativus
• Cucurbita maxima
• Cucurbita pepo
• Datura metel
• Gomphrena globosa
• Gossypium hirsutum
• Ipomoea setosa
• Lycopersicon esculentum
• Macroptilium lathyroides
• Petunia × hybrida
• Phaseolus vulgaris
• Physalis peruviana
• Ricinus communis
• Solanum melongena
• Solanum tuberosum
• Spinacia oleracea
• Zea mays

Families containing susceptible hosts

• Convolvulaceae (1/2)
• Euphorbiaceae (3/4)
• Solanaceae (10/17)
• Urticaceae (1/1)

Families containing insusceptible hosts

• Amaranthaceae (1/1)
• Chenopodiaceae (5/5)
• Convolvulaceae (1/2)
• Cucurbitaceae (5/5)
• Euphorbiaceae (1/4)
• Gramineae (1/1)
• Leguminosae-Papilionoideae (2/2)
• Malvaceae (1/1)
• Solanaceae (7 /17)

Sources of host-range data

Storey and Nichols (1938); Bock and Woods (1983); Bock (1983); Bock et al. (1978); Bock et al. (1981); Anon. (1979); Dubern (1979).

Physical and biochemical properties

Properties of particles in sap

TIP: 55 °C. LIV: 2-4 days. DEP: log₁₀ minus 3 (type strain in sap of Nicotiana clevelandii). Infectivity of sap not changed by treatment with di-ethyl ether. Leaf sap contains few virions. Electron microscopy: virions best detected by immunosorbent electron microscopy.

Purification method

Sequeira and Harrison (1982).

Particle morphology

Virions geminate; not enveloped; 20 nm in diameter; the dimer is 30 nm in length; slightly angular in profile; without a conspicuous capsomere arrangement.

Physical properties

Two sedimenting components in purified preparations; sedimentation coefficient of the fastest (main) component 76 S; of the other(s) 50 S.

Biochemical properties

Virions contain 22 % nucleic acid; 78 % protein.

Genome consists of DNA; single-stranded; circular. Total genome size 5.503 kb. Genome of two parts; largest (or only) genome part the larger 2.779 kb (DNA-1); the 2nd largest 2.724 kb (DNA-2). Genomic nucleic acid isolated by Harrison et al. (1977); Sequeira et al. (1983). Base composition 23.5 % G (DNA-1 24.6%, DNA-2 22.3%); 27.7 % A (DNA-1 26.9%, DNA-2 28.8%); 18.6 % C (DNA-1 19.9%, DNA-2 17.3%); 30.2 % T (DNA-1 28.5%, DNA-2 31.9%). Infectivity decreased when deproteinised with proteases; retained when deproteinised with phenol or detergent (isolated DNA is 1-50% as infective as the same amount of DNA in virions). Poly A region absent. Additional factor not required for infectivity (cloned DNA is infective). Genome has no tRNA-like activity. Nucleotide sequence references: Stanley and Gay (1983); Stanley (1983).

NCBI sequence data (Entrez search)

Sequence database accession code(s)

• J02057 Em(40)_vi:GE1G Gb(84)_vi:CLV1G Cassava latent virus (West Kenyan 844), DNA 1 of complete genome. 4/90 2,779bp.
• J02058 Em(40)_vi:GE2G Gb(84)_vi:CLV2G Cassava latent virus (west kenyan 844), dna 2 of complete genome. 4/90 2,724bp.
• X17095 Em(40)_vi:GEN1G Gb(84)_vi:GEN1G African cassava mosaic virus (Nigerian strain) DNA 1. 9/93 2,781bp.
• X17096 Em(40)_vi:GEN2G Gb(84)_vi:GEN2G African cassava mosaic virus (Nigerian strain) DNA-2. 9/93 2,725bp.
• X68318 Em(40)_vi:ACPPCR6 Gb(84)_vi:ACPPCR6 African Cassava Mosaic Virus gene for coat protein (clone pPCR6). 7/93 852bp.
• X68319 Em(40)_vi:ACPPCR5 Gb(84)_vi:ACPPCR5 African Cassava Mosaic Virus gene for coat protein (clone pPCR5). 7/93 852bp.
• X68320 Em(40)_vi:ACPPCR4 Gb(84)_vi:ACPPCR4 African Cassava Mosaic Virus gene for coat protein (clone pPCR4). 7/93 852bp. 5 sequences.

Features of the genome

Features of the genome: the two circular genome DNA species share a sequence of 193 nucleotides which contains a stem and loop structure of 33 nucleotides. Transcription in both directions. DNA-1 encodes one protein of more than 15 kDain the plus (virion DNA) sense and three proteins more than 15 kDain the minus sense. DNA-2 encodes one protein more than 15 kDain each sense. Possible promoter and terminator and polyadenylation signals are found in all six ORFs. RNA transcripts of the expected sizes are found.

Non-genomic nucleic acid found in the virions; Non-genomic nucleic acid is derived from DNA-2. Sub-genomic mRNA found in infected cells.

Features of proteins

Virion protein(s) one; M_r 31800 (»700 (Sequeira, 1982) or 30200 when translated from the nucleotide sequence (Stanley and Gay, 1983)). Method of preparation: Bock et al. (1977); Sequeira (1982). Amino acid sequence: Stanley et al. (1985). Virion proteins not glycosylated (Sequeira, 1982).

Virus-coded non-virion proteins identified by genomic sequence analysis; five proteins found. M_r 40300. M_r of 2nd largest 33700; 2L1, which assists virus movement. M_r of 3rd 29300; 2R1, assisting virus movement. M_r of 4th 15800. M_r of 5th and smaller 15100.

Replication

Replication does not depend on a helper virus.

Cytopathology

Virions found in mesophyll, epidermis, phloem and companion cells; in nuclei. Inclusions present in infected cells; are unusual in shape; a granular material; they contain virions. Other cellular changes: the production of fibrillar rings in the nuclei of phloem parenchyma cells (Horvat and Verhoyen, 1981; Adejare and Coutts, 1982).

Taxonomy and relationships

bigeminivirus: Geminiviridae

Virus(es) with serologically related virions

Bean golden mosaic (SDI:2) (Sequeira and Harrison, 1982), squash leaf curl (Cohen et al., 1983), tomato golden mosaic (SDI:2) (Stein et al., 1983), euphorbia mosaic (Roberts et al., 1984) and many other whitefly transmitted geminiviruses (M. Aiton and B.D. Harrison, unpublished information).

Additional comments on relationships

There are sequence homologies between the larger genome part (DNA-1) of African cassava mosaic virus and the DNA of bean golden mosaic, tomato golden mosaic, tobacco leaf curl and tomato leaf curl viruses (Roberts et al., 1984). DNA-1 of African cassava mosaic virus shows clear sequence similarities with bean golden mosaic virus in coding regions, but little in non-coding regions (Hamilton et al., 1984; Harrison, 1985). No serological relationship or genome homology has been found between African cassava mosaic virus and any monogeminiviruses.

The close serological relationship between biologically distinct geminiviruses can lead to difficulties in virus identification, especially when plant species not previously recorded as hosts are infected. However, African cassava mosaic virus does not infect Phaseolus vulgaris or Cucurbita pepo whereas bean golden mosaic and squash leaf curl viruses do. In hybridization tests, African cassava mosaic virus DNA-2 probes do not react with extracts of plants infected with bean golden mosaic, tobacco golden mosaic or tobacco leaf curl and allied geminiviruses (Roberts et al., 1984).

Best tests for diagnosis

African cassava mosaic virus is the only geminivirus reported from cassava in Africa. However, in South America, similar symptoms are caused by cassava common mosaic potexvirus which also causes local lesions in Chenopodium amaranticolor and Gomphrena globosa and is not transmitted by Bemisia tabaci (Costa and Kitajima, 1972). Viruses associated with two other mosaic diseases of cassava in Colombia are not sap-transmissible to Nicotiana benthamiana. Indian cassava mosaic virus is now considered to be a separate geminivirus.

Comments and References

References

• Adejare, G.O. and Coutts, R.H.A. (1982). Phytopath. Z. 103: 87.
• Anon. (1979). Rep. Int. Inst. Trop. Agric. 1978, p.107.
• Bock, K.R. (1983). In: Plant Virus Epidemiology, p. 337; eds R.T. Plumb and J.M. Thresh. Oxford, Blackwell Scientific Publications.
• Bock, K.R. (1984). ODA Crop Virol. Res. Proj. Kenya Agric. Res. Inst., Final Report. Overseas Development Administration, London.
• Bock, K.R. and Guthrie, E.J. (1982). Trop. Pest Manag. 28: 219.
• Bock, K.R. and Harrison, B.D. (1985). CMI/AAB Descr. Pl. Viruses No. 297, 6 pp.
• Bock, K.R. and Woods, R.D. (1983). Plant Dis. 67: 994.
• Bock, K.R., Guthrie, E.J. and Figueiredo, G. (1981). Ann. appl. Biol. 99: 151.
• Bock, K.R., Guthrie, E.J. and Meredith, G. (1978). Ann. appl. Biol. 90: 361.
• Bock, K.R., Guthrie, E.J., Meredith, G. and Barker, H. (1977). Ann. appl. Biol. 85: 305.
• Chant, S.R. (1958). Ann. appl. Biol. 46: 210.
• Cohen, S., Duffus, J.E., Larsen, R.C., Liu, H.Y. and Flock, R.A. (1983). Phytopathology 73: 1669.
• Costa, A.S. and Kitajima, E.W. (1972). CMI/AAB Descr. Pl. Viruses No. 90, 4 pp.
• Dubern, J. (1979). Phytopath. Z. 96: 25.
• Fargette, D., Fauquet, C. and Thouvenel, J.-C. (1985). Ann. appl. Biol. 106: 285.
• Hahn, S.K., Terry, E.R. and Leuschner, K. (1980). Euphytica 29: 673.
• Hamilton, W.D.O., Stein, V.E., Coutts, R.H.A. and Buck, K.W. (1984). EMBO J. 3: 2197.
• Harrison, B.D. (1985). Ann. Rev. Phytopath. 23: 55.
• Harrison, B.D., Barker, H., Bock, K.R., Guthrie, E.J., Meredith, G. and Atkinson, M. (1977). Nature, Lond. 270: 760.
• Horvat, F. and Verhoyen, M. (1981). Parasitica 37: 27119.
• Kaiser, W.J. and Louie, R. (1982). Plant Dis. 66: 475.
• Roberts, I.M., Robinson, D.J. and Harrison, B.D. (1984). J. gen. Virol. 65: 1723.
• Robertson, I.A.D. (1984). Cassava Whitefly Proj. Crop Virol. Res. Proj. Kenya Agric. Res. Inst., Final Report. Overseas Development Administration, London.
• Sequeira, J.C. (1982). Ph.D. Thesis, University of Dundee, U.K.
• Sequeira, J.C. and Harrison, B.D. (1982). Ann. appl. Biol. 101: 33.
• Sequeira, J.C., Harrison, B.D. and Duncan, G.H. (1983). Rep. Scottish Crop Res. Inst. 1982, p. 193.
• Stanley, J. and Gay, M.R. (1983). Nature, Lond 301: 260.
• Stein, V.E., Coutts, R.H.A. and Buck, K.W. (1983). J. gen. Virol. 64: 2493.
• Storey, H.H. and Nichols, R.F.W. (1938). Ann. appl. Biol. 25: 790.
• Townsend, R., Stanley, J., Curson, S.J. and Short, M.N. (1985). EMBO J. 4: 33.
• Warburg, O. (1894). Mitt. Deutsch. Schutzgeb. 7: 131.

Cite this publication as: Brunt, A.A., Crabtree, K., Dallwitz, M.J., Gibbs, A.J., Watson, L. and Zurcher, E.J. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 20^th August 1996.' URL http://biology.anu.edu.au/Groups/MES/vide/

Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993) should also be cited.