Details of DPV and References
DPV NO: 335 September 1988
Species: Dioscorea latent virus | Acronym: DLV
Dioscorea latent virus
Sue Phillips AFRC Institute of Horticultural Research, Littlehampton, Sussex, England, BN17 6LP
A. A. Brunt AFRC Institute of Horticultural Research, Littlehampton, Sussex, England, BN17 6LP
- 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 reported by Lawson et al. (1973), partially characterised by Waterworth et al. (1974), and more fully described by Phillips et al. (1986).
A virus with filamentous particles about 445 x 13 nm, known to occur naturally only in Dioscorea composita and D. floribunda in Central America. It has no known vector but is readily transmissible by inoculation of sap to species in six families.
The virus alone causes no obvious symptoms in Dioscorea composita and D. floribunda, its only known natural hosts, but it often occurs together with dioscorea green banding virus which induces mosaic and green-banding leaf symptoms (Lawson et al., 1973; Hearon et al., 1978).
Reported only from Puerto Rico, but probably occurs in other parts of Central America where its two natural hosts are cultivated.
Host Range and Symptomatology
The virus is transmissible by mechanical inoculation of sap to D. composita and D. floribunda and to 13 of 34 other species in five of 12 families. It induces symptomless infection in inoculated leaves only of most experimental hosts, but symptomless systemic infection also in Nicotiana benthamiana and N. megalosiphon (Hearon et al., 1978; Phillips et al., 1986).
- Philodendron selloum.Faint yellowing and mottling of inoculated leaves 3 wk after inoculation. No systemic infection.
- Dioscorea composita and D. floribunda. Symptomless infection in
systemically infected leaves.
- Nicotiana benthamiana and N. megalosiphon. Symptomless infection in inoculated and uninoculated leaves.
- Nicotiana megalosiphon.Infected plants, although symptomless, are good sources of virus for purification.
- No satisfactory local lesion assay host is available. Nicotiana megalosiphon, if tested subsequently for the presence of virus by serological and/or electron microscopical procedures, can be used indirectly for assays.
Transmission by Vectors
Not transmitted by Aphis gossypii or Myzus persicae in either the persistent or the non-persistent manner (Lawson et al., 1973; Waterworth et al., 1974; Phillips et al., 1986).
Transmission through Seed
Not seed-borne in Nicotiana megalosiphon (Phillips et al., 1986).
The virus is a good immunogen; antisera with titres of 1/4096 to 1/16,000 in precipitin tube tests have been obtained from rabbits injected intramuscularly on each of 2 to 4 occasions with c. 1 mg virus emulsified with Freunds complete adjuvant (Waterworth et al., 1974; Phillips et al., 1986).
The virus has properties typical of members of the potexvirus group. It shows a distant serological relationship to commelina X and lily X viruses, but is serologically unrelated to cactus X, clover yellow mosaic, cymbidium mosaic, hydrangea ringspot, narcissus mosaic, nerine X (Agapanthus strain), papaya mosaic (Ullucus strain), pepino mosaic, potato X, potato aucuba mosaic, viola mottle or white clover mosaic viruses (Waterworth et al., 1974; Phillips et al., 1986).
Stability in Sap
Sap from systemically infected Nicotiana megalosiphon leaves remains infective after heating for 10 min at 75-80 but not 85°C, after at least 12 months at 22°C and after dilution to 10-6 but not 10-7 (Phillips et al., 1986).
Although virus can be recovered from infected Dioscorea floribunda and D. composita leaves, purification is hindered by the presence of mucilaginous substances (Waterworth et al., 1974). Nicotiana megalosiphon is a better source of virus for purification, yielding up to 30 mg virus/kg leaf tissue using the following method (Phillips et al., 1986). Grind leaves (1 g/3 ml) in 0.07 M neutral phosphate buffer containing 1 ml/l 2-mercaptoacetic acid, express the extract through cheesecloth and, with stirring, slowly add Triton X-100 (50 ml/l). After 30 min, subject the mixture to two cycles of differential centrifugation (20 min at 12,000 g; 75 min at 65,000 g). Purify the virus further by rate zonal sucrose density gradient centrifugation (2.5 h at 85,000 g in 100-400 g/l sucrose density- gradient columns).
Properties of Particles
Sedimentation coefficient (s20,W): 111 S. Aggregated particles, probably end-to-end dimers, sediment at 131 S (Phillips et al., 1986).
Buoyant density in caesium chloride: 1.33 g cm-3.
The virus has slightly flexuous filamentous particles with a modal length of 445 nm and a diameter of 13 nm when mounted in sodium phosphotungstate (Lawson et al., 1973; Waterworth et al., 1974; Phillips et al., 1986).
Nucleic acid: RNA, single-stranded, c. 5% of the particle weight. One species, of M. Wt 2.3 x 106 (estimated under denaturing conditions by electrophoresis in 1.5% agarose gels).
Protein: One species of polypeptide, M. Wt 24,900; a second component of M. Wt 23,100 present in some preparations is probably a degradation product of the former (Phillips et al., 1986).
Relations with Cells and Tissues
Infected Dioscorea floribunda plants contain amorphous, vacuolated, cytoplasmic inclusions, and banded inclusions consisting of closely-packed virus particles (Hearon, 1974; Hearon et al., 1978).
Although the particles of dioscorea latent virus are shorter than those of most other potexviruses, their morphology, physico-chemical properties, in vivo occurrence and distant serological relationship to lily X and commelina X viruses indicate that the virus is a distinct but definite member of the potexvirus group.
Dioscorea composita and D. floribunda produce tubers that are major sources of diosgenin, a sapogenin used in the commercial production of cortisone and progesterone. These two species, indigenous to Mexico and some South American countries, are the only known natural hosts of dioscorea latent virus; it is especially interesting that the virus has not been detected in edible yam species such as D. alata, D. esculenta and D. bulbifera.
References list for DPV: Dioscorea latent virus (335)
- Hearon, Proc. Am. Phytopath. Soc. 1: 151, 1974.
- Hearon, Corbett, Lawson, Gillaspie & Waterworth, Phytopathology 68: 1137, 1978.
- Lawson, Hearon, Smith & Kahn, Phytopathology 63: 1435, 1973.
- Phillips, Piggott & Brunt, Ann. appl. Biol. 109: 137, 1986.
- Waterworth, Lawson & Kahn, J. Agric. Univ. P. Rico 58: 351, 1974.