Details of DPV and References
DPV NO: 256 July 1982
Species: Tephrosia symptomless virus | Acronym: TeSV
Tephrosia symptomless virus
K. R. Bock Overseas Development Administration, Crop Virology Research Project, Kenya Agriculture Research Institute, P.O. Box 30148, Nairobi, Kenya
- 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
Described by Bock, Guthrie, Figueiredo & Woods (1981).
A virus with c. 33 nm isometric particles that sediment as a single component and resemble those of tombusviruses. It has a very restricted experimental host range and has been isolated only from species of Tephrosia in eastern Kenya. It occurs commonly in the field but its mode of transmission is not known.
Infection in Tephrosia villosa, a wild leguminous plant, is symptomless, both in the field and in mechanically inoculated plants in the glasshouse. The virus causes no symptoms in any other susceptible species of Tephrosia except T. uncinatum, in which it may cause a mild mottle. It has not been isolated from any economically important legume nor has it been detected in any other wild leguminous plant.
Recorded only in eastern districts of Kenya but possibly occurs throughout the range of its main host, Tephrosia villosa, which extends widely in eastern and southern Africa from sea level to c. 1300 m.
Host Range and Symptomatology
Apparently restricted to the Tephroseae (Tephrosia) and Phaseoleae (Canavalia, Glycine, Phaseolus, Voandzeia) in the Leguminosae. Thirty two other species in the Leguminosae and 28 species in eight other families were not infected (Bock et al., 1981).
- Glycine max(soybean). Prominent irregular systemic mottle (Fig. 2); very susceptible to infection.
- Phaseolus vulgaris (French bean). Local chlorotic or necrotic lesions
in many cvs (Canadian Wonder, Long Tom, Premier, Tendercrop, Topcrop);
no systemic infection.
- Tephrosia villosa. Symptomless systemic infection.
- Chenopodium amaranticolor, C. quinoa and Gomphrena globosa are not susceptible.
- Tephrosia villosa. Symptomless systemic infection.
Propagation and assay species
- Glycine max.No satisfactory local lesion host is known.
No evidence of strain differences among many isolates tested.
Transmission by Vectors
Vector unknown. Aphis craccivora and Apion sp. (Curculionidae) did not transmit (Bock et al., 1981).
Transmission through Seed
Apparently not seed-borne in Tephrosia villosa or Glycine max (Bock et al., 1981).
Strongly immunogenic in rabbits. An antiserum with a titre of 1/1024 in gel diffusion tests has been prepared.
The properties of the virus (M. Wt of the single RNA and single coat protein species, sedimentation coefficient and buoyant density in CsCl) suggest affinities with the tombusvirus group. However, the virus did not react in gel diffusion tests with antisera to any of 44 viruses with isometric particles, including carnation Italian ringspot, carnation mottle, cymbidium ringspot, narcissus tip necrosis, pelargonium leaf curl, saguaro cactus, tomato bushy stunt and turnip crinkle (Bock et al., 1981). In subsequent tests, no relationship was detected to elderberry latent virus (A. T. Jones, unpublished data).
Stability in Sap
In soybean sap, infectivity is lost after dilution 10-5 to 10-6, or after heating for 10 min at 85-90°C, but survives for at least 3 weeks at 18-20°C and for at least 6 months at -12°C.
(Bock et al., 1981). Homogenize infected soybean leaves in 0.06 M phosphate buffer (2 ml/g tissue) containing 0.001 M sodium ethylenediamine-tetraacetate and 0.1% sodium thioglycollate (pH 7.5). Clarify with an equal volume of a mixture (1:1) of n-butanol and chloroform; concentrate by two or three cycles of differential centrifugation, resuspending pellets in 0.01 M phosphate buffer, pH 7.7. Further purification may be achieved by sucrose density gradient centrifugation.
Properties of Particles
Particles in purified preparations (Fig. 4) are isometric, c. 33 nm in diameter when stained in 2% phosphotungstate, pH 6.8.
Single sedimenting component (Fig. 3); sedimentation coefficient (s20, w) (svedbergs): c. 127 at infinite dilution.
A260/A280: 1.45-1.50 (not corrected for light-scattering).
Amax(c. 259)/Amin(c. 243): 1.24-1.37 (not corrected for light-scattering).
Buoyant density in CsCl: 1.361 g/cm3.
The virus particles form a single density component in both CsCl and Cs2SO4 isopycnic gradients.
Nucleic acid: RNA, single-stranded, M. Wt c. 1.5-1.6 x 106. About 20% of the particle weight, estimated from the buoyant density in CsCl and A260/A280 ratio.
Protein: Single species, M. Wt c. 42,000, by SDS-polyacrylamide gel electrophoresis.
Relations with Cells and Tissues
Although tephrosia symptomless virus is widespread in T. villosa in coastal districts of Kenya, it has not been found in any other wild or cultivated legume: an apparent reflection of a very narrow experimental host range. It shares several characteristics with members of the tombusvirus group but seems not to be serologically related to any of them or to other similar viruses. It is however readily identified by serological tests.
References list for DPV: Tephrosia symptomless virus (256)
- Bock, Guthrie, Figueiredo & Woods, Ann. appl. Biol. 97: 277, 1981.