Plant Viruses Online   

Descriptions and Lists from the VIDE Database

Carrot mottle mimic umbravirus

Index

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

Data collated by M.J. Gibbs, 1995.

Nomenclature

ICTV decimal code

78.0.1.DE.01

Host range and symptoms

Natural host range and symptoms

Symptoms persist.

Daucus carota - systemic yellowing and mottling, stunting.

Transmission

Transmitted by a vector; an insect; probably Cavariella aegopodii; Aphididae. Transmitted in a persistent manner. Virus requires, for vector transmission, a helper virus (carrot red leaf luteovirus). The virus genome is probably transcapsidated in the virions of the helper virus. Virus transmitted by mechanical inoculation.

Geographical distribution

Found, but with no evidence of spread, in Australia, New Zealand and the U.S.A.; but may have been confused with carrot mottle umbravirus.

Experimental host range

Few (<3) families susceptible. Experimentally infected plants mostly show vein necrosis.

Diagnostically susceptible host species and symptoms

Nicotiana megalosiphon - necrotic ringspots, systemic necrotic and chlorotic lesions, mostly along major veins.

Maintenance and propagation hosts

Nicotiana megalosiphon, N. clevelandii.

Assay hosts (Local lesions or Whole plants)

Nicotiana megalosiphon (W), N. clevelandii (W).

Susceptible host species

• Anthriscus cerefolium
• Coriandrum sativum
• Daucus carota
• Nicotiana benthamiana
• Nicotiana clevelandii
• Nicotiana glutinosa
• Nicotiana megalosiphon

Families containing susceptible hosts

• Solanaceae (4/4)
• Umbelliferae (3/3)

Physical and biochemical properties

Properties of particles in sap

Leaf sap contains few virions (and these have the coat protein of carrot red leaf luteovirus).

Biochemical properties

Genome consists of RNA; single-stranded; linear. Total genome size 4.203 kb. Genome unipartite; largest (or only) genome part 4.203 kb. Genomic nucleic acid isolated by as dsRNA by Franklin column chromatography using Whatman CF-11 fibrous cellulose powder; as described for carrot mottle umbravirus by Murant et al. (1985). Base composition 27 % G; 25 % A; 25.5 % C; 22.4 % U. Infectivity retained when deproteinised with proteases. Poly A region absent. Additional factor not required for infectivity. Genome has no tRNA-like activity. Nucleotide sequence references: Gibbs (1995).

Features of the genome

Features of the genome: Four ORFs. ORF1 encodes a protein that may be part of the viral replicase, ORF2 encodes the RNA dependent RNA polymerase, ORF3 encodes a protein of unknown function and ORF4 encodes the movement protein gene. ORF2 overlaps ORF1 and is translated after a -1 ribosomal frameshift, ORFs 3&4 also overlap and are translated from a sub-genomic RNA.

Non-genomic nucleic acid found in the virions; is subgenomic mRNA. Sub-genomic mRNA found in infected cells; c. 1.5kb co-terminal with 3´ end of the genome. 2 virus specified dsRNA species found in infected cells. Size of largest virus specified dsRNA 4.2 kbp; 2nd largest c. 1.5 kbp.

Features of proteins

Virion protein(s) none.

Cytopathology

Inclusions present in infected cells; are membranous bodies; they do not contain virions.

Taxonomy and relationships

Umbravirus

Additional comments on relationships

Genome sequence comparisons show the virus to be most closely related to RNA-2 of pea enation mosaic enamovirus, in addition the polymerase sequences show affinities to carmoviruses, dianthoviruses, type 1 and 2 luteoviruses, necroviruses, machlomoviruses, tombusviruses, beet western yellows ST9 associated-RNA and oat chlorotic stunt virus. Comparisons of movement protein sequences show affinities with bromo- and cucumoviruses.

Best tests for diagnosis

Often confused with carrot mottle umbravirus, distinguished by infection of Nicotiana megalosiphon and N. benthamiana; carrot mottle mimic virus induces a mild chlorotic mottle in N. benthamiana and severe symptoms in N megalosiphon, carrot mottle virus induces a more severe chlorotic mottle in N. benthamiana, but no symptoms in N. megalosiphon.

Comments and References

References

• Gibbs, M.J. (1991). Grad. Dip. Thesis, Aust. Nat. Univ.
• Gibbs, M.J. (1995). D. Phil. Thesis, Univ. Oxford.
• Murant, A.F., Waterhouse, P.M., Raschke, J.H. and Robinson, D.J. (1985). J. gen. Virol. 66: 1575.

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.