27
October 1970
Family: Alphaflexiviridae
Genus: Potexvirus
Species: Cymbidium mosaic virus
Acronym: CymMV


Cymbidium mosaic virus

R. I. B. Francki
Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, South Australia

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 Jensen (1951).

Selected synonyms

Cymbidium black streak virus (Rev. appl. Mycol. 30: 469)
Orchid mosaic virus (Rev. appl. Mycol. 23: 261)

An RNA-containing virus with flexuous filamentous particles c. 475 x 13 nm. Readily transmissible by sap inoculation to a narrow range of host plants. Causes diseases in several genera of orchids. No known vector. World-wide distribution.

Main Diseases

Causes mosaic (Fig.1, Fig.2) and necrosis in several genera of orchids (Jensen, 1951; Jensen & Gold, 1955; Murakishi, 1958a, 1958b; Kado & Jensen, 1964). Together with a strain of tobacco mosaic virus causes blossom brown necrotic streak in Cattleya (Thornberry & Phillippe, 1964).

Geographical Distribution

World-wide in cultivated orchids.

Host Range and Symptomatology

Infects species in the Orchidaceae and a few in other families. Transmissible by sap inoculation, for example, to the following:

Diagnostic species

Chenopodium amaranticolor. Slow-developing, large, blotchy lesions in inoculated leaves, not earlier than 20 days after inoculation (Fig.3).

Cassia occidentalis, C. tora and C. bicapsularis. Small lesions in inoculated leaves within 5 days after inoculation (Fig.4).

Datura stramonium. Slow-developing, necrotic lesions in inoculated leaves, not earlier than 10 days after inoculation (Fig.5).

Propagation species

Cymbidium plants are suitable for maintaining cultures and as a source of virus for purification (Corbett, 1960; Francki, 1966). Datura stramonium has also been used as a source of virus for purification (Francki, unpublished).

Assay species

Chenopodium amaranticolor, Datura stramonium and Cassia occidentalis are all suitable local-lesion assay plants.

Strains

None reported.

Transmission by Vectors

No known vector.

Transmission through Seed

None reported.

Transmission by Dodder

No information.

Serology

The virus is strongly immunogenic. Serological tube-precipitin or gel-diffusion tests are convenient. A single precipitin band is produced in gel-diffusion tests.

Relationships

A member of the potato virus X group: a distant serological relationship to potato virus X has been reported and it has particles of similar length (Brandes & Bercks, 1965).

Stability in Sap

In Cymbidium sap, the thermal inactivation point (10 min) is 65-70°C and sap remains infective for at least 7 days at room temperature. Stable in the presence of organic solvents such as chloroform.

Purification

Easily purified by differential centrifugation. Yields of up to 360 mg virus may be obtained from 1 kg of Cymbidium leaves (Kado & Jensen, 1964; Francki, 1966).

Properties of Particles

Appear similar to those of potato virus X but details are unknown.

Particle Structure

Particles are flexuous filaments with helical symmetry about 475 nm long and 13 nm wide as observed in electron micrographs (Fig.6).

Particle Composition

Contains about 6% RNA (Francki, unpublished).

Relations with Cells and Tissues

No information.

Notes

Tobacco mosaic virus is also common in orchids but can easily be distinguished from cymbidium mosaic virus by testing on herbaceous hosts, serological testing or examination of leaf-dip preparations by electron microscopy.

References

  1. Brandes & Bercks, Adv. Virus Res. 11: 1, 1965.
  2. Corbett, Phytopathology 50: 346, 1960.
  3. Francki, Aust. J. biol. Sci. 19: 555, 1966.
  4. Jensen, Phytopathology 41: 401, 1951.
  5. Jensen & Gold, Phytopathology 45: 327, 1955.
  6. Kado & Jensen, Phytopathology 54: 974, 1964.
  7. Murakishi, Phytopathology 48: 132, 1958a.
  8. Murakishi, Phytopathology 48: 137, 1958b.
  9. Thornberry & Phillipe, Pl. Dis. Reptr 48: 936, 1964.


Figure 1

Infected Cymbidium plant.

Figure 2

Mild mosaic in Cymbidium leaf.

Figure 3

Lesions in inoculated leaf of Chenopodium amaranticolor.

Figure 4

Lesions in inoculated leaf of Cassia occidentalis.

Figure 5

Lesions in inoculated leaf of Datura stramonium.

Figure 6

Virus particles from purified preparation in uranyl acetate. Bar represents 500 nm.