Parsnip mosaic virus
A. F. Murant
Scottish Horticultural Research Institute, Invergowrie, Dundee, Scotland
Contents
Introduction
- Described by Murant, Munthe & Goold (1970).
- A virus with flexuous filamentous particles about 730-760 x 14 nm,
transmitted by aphids after brief acquisition feeds and by mechanical
inoculation of sap. Infects several umbelliferous species and a few species in
other families. Found in UK.
Main Diseases
Causes a mild mosaic disease of parsnip (
Pastinaca sativa). It occurs
commonly in parsnip crops in Britain, often in mixed infections with other
viruses, such as
parsnip yellow fleck and parsnip mottle (
Murant & Goold,
1968), but its economic importance, if any, is unknown.
Geographical Distribution
Reported only from UK.
Host Range and Symptomatology
Infects several species in the Umbelliferae and also a few members of the
Amaranthaceae, Chenopodiaceae and Scrophulariaceae. Transmissible by manual
inoculation of sap.
- Diagnostic species
- Chenopodium amaranticolor
. Discrete necrotic local lesions 1-2 mm
diameter in 6 days, later developing chlorotic margins (Fig.1). Subsequently
the inoculated leaves become chlorotic and absciss. No systemic infection.
- C. quinoa. Irregular papery necrotic local lesions 1-2 mm diameter
in 6 days (Fig.2). Subsequently the lesions coalesce and inoculated leaves
become yellow and absciss. No systemic infection.
- Anthriscus cerefolium (chervil). Fine systemic veinal necrosis visible
on the youngest leaves after 8 days, followed by veinal chlorosis and distortion
(Fig.4). Plants are stunted but not usually killed.
- Coriandrum sativum (coriander). Severe systemic veinal necrosis and
distortion of youngest leaves in 8-14 days (Fig.3). Plants may die after 2-3
weeks.
- Pastinaca sativa (parsnip). Yellow systemic vein-banding in 8-10 days.
Plants subsequently become almost symptomless.
- Propagation species
- The virus can be propagated in inoculated leaves of Chenopodium quinoa.
Isolates can be maintained in Coriandrum sativum.
- Assay species
- Chenopodium amaranticolor and C. quinoa are good local lesion
hosts. Chervil and coriander are suitable test plants for experiments on
transmission by aphids.
Strains
None reported.
Transmission by Vectors
Transmitted in the non-persistent manner by the aphids
Cavariella aegopodii, C. theobaldi and
Myzus persicae. Aphids
acquired virus after 2-5 min feeding.
Starving the aphids for 2-4 hr before the acquisition feed increased the
efficiency of transmission
(
Murant et al., 1970).
Transmission through Seed
No information.
Transmission by Dodder
No information.
Serology
Antiserum with a titre of 1/256 was obtained from a rabbit given a single
intramuscular injection with partially purified virus emulsified with Freund’s
complete adjuvant (
Murant et al., 1970). Ring precipitin or
microprecipitin tests can be done using partially purified virus preparations
from
Chenopodium quinoa as antigen.
Relationships
In particle morphology and in its
in vivo and
in vitro
properties, parsnip mosaic virus resembles members of the
potato virus Y
group (potyviruses). However, no serological relationship was detected to
any of eleven viruses in this group (
Murant et al., 1970), including
two that infect umbelliferous plants,
celery mosaic and
clover yellow vein.
In more recent work (
Murant & Goold, 1972) no reaction was obtained with
antisera to viruses from parsley and poison hemlock studied by
Sutabutra &
Campbell (1971).
Stability in Sap
In extracts of
Chenopodium quinoa leaves, the virus lost infectivity
after dilution to 10
-3-10
-4, or storage for 10 min at
55-58°C or 7-10 days at 18°C (
Murant et al., 1970).
Purification
Murant et al. (1970) used the following procedure: homogenize
Chenopodium quinoa inoculated leaves (100 g) in 200 ml 0.1 M borate, 0.01
M ethylene diamine tetra acetate, pH 8.0, containing 0.1% thioglycollic acid,
and filter through cheesecloth. Emulsify the filtrate with an equal volume of
chloroform and centrifuge at low speed. Concentrate by one cycle of differential
centrifugation, dispersing the high speed pellets in borate/EDTA buffer, pH 8.0.
Precipitate the virus by adjusting the pH to 5.0, then resuspend at pH 8.0 the
pellets produced by low speed centrifugation. Remove phytoferritin-like particles
of host origin by exclusion chromatography in a column of 2% agarose beads,
having first dialysed the preparation against 0.15 M NaCl, 0.01 M EDTA, pH 8.0,
the buffer used as the eluant for the column. Virus preparations obtained in this
way are substantially free from host material but many particles are aggregated.
Aggregation can be largely prevented by eliminating the pH 5.0 precipitation step.
Properties of Particles
Sedimentation coefficient,
s20,w: 149 S.
Particle Structure
The particles are flexuous filaments 14 nm wide with a modal length of 736 nm
in sap from
Chenopodium quinoa containing phosphotungstate at pH 6.8
(
Murant et al., 1970). In partially purified preparations (
Fig.5) the
particles have a modal length of 755 nm.
Particle Composition
No information.
Relations with Cells and Tissues
Virus particles were rarely seen in ultrathin sections of systemically infected
coriander leaf cells, but the cells contained abundant pinwheel and bundle
inclusions (
Fig.6) resembling those described for other
potyviruses
(
Murant
& Roberts, 1971).
Notes
Several viruses with filamentous particles occur in umbelliferous plants.
Celery mosaic virus was considered to be restricted to the Umbelliferae (
Shepherd
& Grogan, 1971) but there are several recent reports that some isolates thought
to be celery mosaic virus can infect
Chenopodium species. Such isolates
were obtained from celery by
Wolf (1969), from carrot by
Iwaki & Komuro (1970)
and from parsley and poison hemlock by
Sutabutra & Campbell (1971). Only the
last two viruses were shown to be serologically related to celery mosaic virus,
though distinguishable from it. Parsnip mosaic virus does not react with antisera
to these two viruses nor with antiserum to celery mosaic virus itself. Other
viruses with filamentous particles that infect umbelliferous plants include
carrot mosaic (
Chod, 1965), celery latent (
Brandes & Luisoni, 1966) and
clover
yellow vein viruses (
Singh & López-Abella 1971). These, however,
infect several non-umbelliferous species systemically, whereas parsnip mosaic
virus does not.
There are similarities in host range between parsnip mosaic virus and a virus
with filamentous particles from parsley (Férault et al., 1969)
and another of unknown particle morphology from Heracleum sphondylium
(Polák, 1966), but no serological comparisons have been reported.
References
- Brandes & Luisoni, Phytopath. Z. 57: 277, 1966.
- Chod, Ochr. Rost. 3: 49, 1965.
- Férault, Lapierre, Spire & Bertrandy, Annls Phytopath. 1: 303, 1969.
- Iwaki & Komuro, Ann. phytopath. Soc. Japan 36: 36, 1970.
- Murant & Goold, Ann. appl. Biol. 62: 123, 1968.
- Murant & Goold, Rep. Scott. hort. Res. Inst. 1971 64, 1972.
- Murant, Munthe & Goold, Ann. appl. Biol. 65: 127, 1970.
- Murant & Roberts, J. gen. Virol. 10: 65, 1971.
- Polák, Biologia Pl. 8: 73, 1966.
- Shepherd & Grogan, CMI/AAB Descriptions of Plant Viruses 50, 4 pp., 1971.
- Singh & López-Abella, Phytopathology 61: 333, 1971.
- Sutabutra & Campbell, Pl. Dis. Reptr 55: 328, 1971.
- Wolf, Mber. dt. Akad. Wiss. Berl. 11: 293, 1969.
Lesions in inoculated leaf of Chenopodium amaranticolor.
Lesions in inoculated leaf of C. quinoa.
Systemic veinal necrosis and distortion in coriander (Coriandrum
sativum).
Systemic vein-yellowing and distortion in chervil (Anthriscus
cerefolium).
Particles in a partially purified preparation mounted in 2% potassium
phosphotungstate, pH 6.8. Bar represents 250 nm.
Section of systemically infected coriander leaf showing pinwheels linked
(arrows) through the formation of laminated aggregates (LA). Bar represents 200 nm.
