208
July 1979
Family: Secoviridae
Genus: Sadwavirus
Species: Satsuma dwarf virus
Acronym: SDV


Satsuma dwarf virus

T. Usugi
Institute for Plant Virus Research, Yatabe, Ibaraki 300-21, Japan

Y. Saito
Institute for Plant Virus Research, Yatabe, Ibaraki 300-21, Japan

Contents

Introduction
Main Diseases
Geographical Distribution
Host Range and Symptomatology
Strains
Transmission by Vectors
Transmission through Seed
Transmission by Grafting
Transmission by Dodder
Serology
Nucleic Acid Hybridization
Relationships
Stability in Sap
Purification
Properties of Particles
Particle Structure
Particle Composition
Properties of Infective Nucleic Acid
Molecular Structure
Genome Properties
Satellites
Relations with Cells and Tissues
Ecology and Control
Notes
References
Acknowledgements
Figures

Introduction

Described by Yamada & Sawamura (1950).

A virus with isometric RNA-containing particles about 26 nm in diameter, with three centrifugal components. It is transmissible mechanically with difficulty from young leaves of citrus to citrus and to herbaceous plants. The virus has a relatively wide host range. Found in Japan and Turkey. No vector is known.

Main Diseases

Causes stunting, leaf malformation and rosetting of satsuma orange (Citrus unshiu). Characteristically, the leaves produced in spring have the shape of an inverted boat or spoon (Fig.1). Viruses related to satsuma dwarf virus are associated with citrus mosaic, navel orange infectious mottling and natsudaidai dwarf diseases.

Geographical Distribution

Widely distributed in Japan and reported from Turkey (Azeri, 1973).

Host Range and Symptomatology

Restricted in nature to citrus, but can be transmitted mechanically to a relatively wide range of herbaceous species in eight families of dicotyledonous plants (Tanaka & Kishi, 1963; Kishi & Tanaka, 1964; Tanaka & Nakanishi, 1972; Usugi & Saito, 1977). Many citrus plants develop only transient symptoms when infected (Miyakawa, 1969).

Diagnostic species
Chenopodium quinoa. Chlorotic or necrotic local lesions in the inoculated leaves; not systemic (Fig.2).

Physalis floridana. Systemic mottling and malformation (Fig.4).

Sesamum indicum (white sesame). Local lesions in the inoculated leaves; vein-clearing, necrosis, curling and malformation of the upper leaves (Fig.3).

Vigna sinensis (cowpea) cv. Blackeye. Local lesions in the inoculated leaves, mottling and vein-clearing on the upper leaves; necrotic streaks on petioles and stems (Fig.5).

Propagation species
Physalis floridana is a suitable host for maintaining the virus, and is the best source of virus for purification.

Assay species
Chenopodium quinoa can be used for local lesion assays.

Strains

Virus isolates associated with citrus mosaic, navel orange infectious mottling and natsudaidai dwarf diseases are serologically related to satsuma dwarf virus and are considered to be strains (Imada, 1977; Imada, Narisawa & Tanaka, 1977). Satsuma dwarf virus protects satsuma orange against infection with the other strains except that associated with natsudaidai dwarf disease (Tanaka & Yamada, 1969). The strains can be distinguished from one another by the reaction of citrus and herbaceous indicator plants (Tanaka, 1971; Tanaka & Nakanishi, 1972; Tanaka & Yamada, 1972).

Transmission by Vectors

No vectors known.

Transmission through Seed

The virus was transmitted to progeny seedlings through 8.6% of the seeds of infected Phaseolus vulgaris (kidney bean) cv. Satisfaction, but not through seeds of white sesame or Citrus sulcata (Kishi, 1967).

Transmission by Dodder

The virus was not transmitted from infected herbaceous plants to citrus by Cuscuta japonica (Kishi, 1967).

Serology

The virus is moderately immunogenic giving antiserum with a gel-diffusion titre of 1/320 and a complement fixation titre of 1/640. In gel-diffusion tests the virus produces one line of precipitate (Usugi & Saito, 1977).

Relationships

The virus did not react with antisera against tomato black ring, tomato ringspot, cherry leaf roll, tobacco ringspot, raspberry ringspot, strawberry latent ringspot, bean pod mottle, cowpea mosaic, cucumber mosaic, citrus leaf rugose (Usugi & Saito, 1977), mulberry ringspot (Tsuchizaki et al., 1971) or grapevine Bulgarian latent viruses (T. Usugi, unpublished data).

Stability in Sap

In sap of Physalis floridana, the thermal inactivation point (10 min) for infectivity is 50-55°C and the dilution end-point is 1/1280-1/2560; infectivity persists for 8-12 days at room temperature (Imada, 1977).

Purification

Harvest Physalis floridana plants about 2 weeks after inoculation, then homogenize at 4°C in 0.1 M sodium citrate containing 0.1% thioglycollic acid (pH 6.8) (3 ml extractant per g tissue). Express the juice through cheesecloth, and add 10 ml magnesium bentonite suspension (50 mg/ml) to every 100 ml extract (Dunn & Hitchborn, 1965). Shake the mixture, and clarify by low-speed centrifugation. Precipitate the virus by adding 25 g ammonium sulphate per 100 ml supernatant fluid. Resuspend the pellets in 0.005 M borate buffer containing 10-3 M EDTA (pH 8.6) and shake with 1/5 vol carbon tetrachloride for 15 min. Centrifuge, and subject the aqueous phase to 1 or 2 cycles of differential centrifugation, resuspending the pellets in the same buffer. Sucrose density-gradient centrifugation can be used for further purification (Usugi & Saito, 1977).

Properties of Particles

Purified virus preparations contain three centrifugal components. Top (T), found in trace amounts, is probably free of RNA: middle (M) and bottom (B) contain RNA. Infectivity is greatest when M and B are mixed.

Sedimentation coefficients (s°20,w) in 0.01 M NaCl (svedbergs): about 119 (M) and 129 (B).

Buoyant density in CsCl (g/cm3): about 1.43 (M) and 1.46 (B) (Usugi & Saito, 1977).

Particle Structure

Particles are isometric, about 26 nm in diameter (Saito et al., 1963) (Fig.6).

Particle Composition

Nucleic acid: RNA, probably single-stranded, comprising about 33% (M) or about 37% (B) of the particle weight, estimated from the buoyant density in CsCl. M component contains a RNA species of M. Wt 1.7 x 106 and B component contains a RNA of M. Wt 1.9 x 106 (T. Usugi, unpublished data).

Protein: Protein, prepared by boiling purified virus for 1 min in 1% sodium dodecyl sulphate + 1% mercaptoethanol, shows two bands in SDS-polyacrylamide gel electrophoresis, with estimated M. Wt 42,000 and 21,000, the two proteins occurring in about equimolar amounts. It is not known whether the two proteins represent distinct polypeptides or derivatives of a single polypeptide (T. Usugi, unpublished data).

Relations with Cells and Tissues

In leaf cells of infected herbaceous plants, electron microscopy reveals (i) tubular structures in cell wall outgrowths, containing single rows of spherical particles (Fig.7), (ii) virus particles in a lattice array and (iii) characteristic vesicular inclusion bodies. No virus particles are observed in the nuclei, chloroplasts, or mitochondria (Saito & Hibino, 1972; Hibino et al., 1977).

Notes

Satsuma orange trees are occasionally infected with citrus tatter-leaf virus. However, satsuma dwarf virus is distinguished from citrus tatter-leaf virus and other sap-transmissible viruses in citrus because it is the only one that induces symptoms in white sesame.

References

  1. Azeri, Pl. Dis. Reptr 57: 149, 1973.
  2. Dunn & Hitchborn, Virology 25: 171, 1965.
  3. Hibino, Tsuchizaki, Usugi & Saito, Ann. phytopath. Soc. Japan 43: 255, 1977.
  4. Imada, Shokubutsu-boeki 31: 399, 1977.
  5. Imada, Narisawa & Tanaka, Ann. phytopath. Soc. Japan 43: 101, 1977.
  6. Kishi, Bull. hort. Res. Stn Japan, Ser. A, 6: 115, 1967.
  7. Kishi & Tanaka, Ann. phytopath. Soc. Japan 29: 142, 1964.
  8. Miyakawa, Ann. phytopath. Soc. Japan 35: 224, 1969.
  9. Saito & Hibino, Proc. 5th Conf. int. Organization of Citrus Virologists, 1972: 217, 1972.
  10. Saito, Kishi, Iwata & Tanaka, Ann. phytopath. Soc. Japan 28: 284, 1963.
  11. Tanaka, Rev. Pl. Protection Res. 4: 81, 1971.
  12. Tanaka & Kishi, Ann. phytopath. Soc. Japan 28: 262, 1963.
  13. Tanaka & Nakanishi, Ann. phytopath. Soc. Japan 38: 212, 1972.
  14. Tanaka & Yamada, Ann. phytopath. Soc. Japan 35: 130, 1969.
  15. Tanaka & Yamada, Proc. 5th Conf. int. Organization of Citrus Virologists, 1972: 71, 1972.
  16. Tsuchizaki, Hibino & Saito, Ann. phytopath. Soc. Japan 37: 266, 1971.
  17. Usugi & Saito, Ann. phytopath. Soc. Japan 43: 137, 1977.
  18. Yamada & Sawamura, Bull. hort. Div. Tokai-Kinki agric. exp. Stn 1: 61, 1950.


Figure 1

Mis-shapen leaves of infected satsuma orange. (Photograph courtesy of Dr. H. Kitajima)

Figure 2

Local lesions in inoculated leaf of Chenopodium quinoa.

Figure 3

Necrosis of systemically infected leaves of Sesamum indicum.

Figure 4

Systemic mottling and malformation in Physalis floridana.

Figure 5

Local lesions in the inoculated leaves and necrotic streaks in the petioles of Vigna sinensis cv. Blackeye.

Figure 6

Virus particles from a purified preparation in phosphotungstate. Bar represents 100 nm.

Figure 7

Tubular structure containing virus particles in cell-wall outgrowth of a leaf cell of systemically infected Vigna sinensis. Bar represents 100 nm.