Beet necrotic yellow vein virus
T. Tamada
Hokkaido Central Agricultural Experiment Station, Naganuma, Hokkaido, Japan
Contents
Introduction
-
Described by
Tamada et al. (1970) and
Tamada & Baba (1973).
-
A virus with straight tubular particles of two or three lengths. It has a narrow
host range and is transmitted by the fungus, Polymyxa betae, and by inoculation
of sap.
Main Diseases
Associated with ‘rhizomania’ disease in sugar beet (
Beta vulgaris)
(
Kanzawa & Ui, 1972).
Diseased sugar beet plants show variable amounts of
chlorosis, yellowing, necrotic vein-yellowing, crinkling, wilting and stunting.
Most of these symptoms seem to be caused by root damage induced by the virus
infection, and depend on the environmental conditions. Also causes yellow mottle
and stunting in spinach (
Spinacia oleracea).
Geographical Distribution
Found in Japan (Hokkaido); possibly occurs in Italy and France.
Host Range and Symptomatology
The virus was transmitted by inoculation of sap to 15 species in the
Chenopodiaceae, to
Tetragonia expansa (Aizoaceae) and to
Gomphrena
globosa (Amaranthaceae); 67 species in 16 families were not infected
(
Tamada & Baba, 1973).
The virus tends to be restricted to inoculated leaves of host
plants; it often becomes systemic in
Beta macrocarpa but rarely in spinach
and sugar beet.
-
Diagnostic species
- Beta vulgaris
(sugar beet). Inoculated leaves develop chlorotic or yellow
lesions 6-8 days after inoculation. The lesions then enlarge and tend to coalesce,
spreading along the veins. Few plants are systemically infected; they show chlorotic
or yellow spotting, yellow vein-banding, vein necrosis, leaf distortion, wilting and
stunting
(Fig.1, Fig.5).
- Beta macrocarpa. Inoculated leaves usually develop chlorotic local lesions,
followed by systemic yellow mottle or yellow flecks with leaf distortion
(Fig.2).
- Chenopodium amaranticolor, C. quinoa. Chlorotic or necrotic lesions
appear in inoculated leaves 5-7 days after inoculation
(Fig.4). Not systemically
infected.
- Tetragonia expansa. Chlorotic, yellowish or necrotic spots and rings,
or concentric rings develop in inoculated leaves, depending on the virus isolate
(Fig.3).
Sometimes infected systemically by YS isolates. This species can be used
for distinguishing strains.
-
Propagation species
- Sugar beet (Beta vulgaris) and Tetragonia expansa (inoculated
leaves) can be used for maintaining cultures and as sources of virus.
Assay species
- Chenopodium amaranticolor
is a good local lesion host
(Fig.4).
- Sugar beet (Beta vulgaris) seedlings are useful for testing transmission
by the vector.
Strains
Isolates have been placed in four groups on the basis of the type of lesions
produced in leaves of
Tetragonia expansa
(
Tamada et al., 1975):
CR
(concentric rings), YS (yellow spots,
Fig.3, right),
CS (pale chlorotic spots or
rings), and NS (necrotic spots or rings,
Fig.3, left). In a few cases YS isolates
infect systemically, causing yellow vein-banding, whereas other isolates always
remain localized in the inoculated leaves. Typical yellow vein or necrotic yellow
vein symptoms in sugar beet are produced only by YS isolates
(
Fig.1,
Fig.5).
Transmission by Vectors
The virus is transmitted by the plasmodiophoromycete fungus,
Polymyxa betae
(
Fig.8).
In naturally affected plants, infection with the virus is correlated
with the occurrence of
P. betae in the rootlets. The virus is transmitted
when suspensions of resting spores or zoospores of the fungus from infected roots
are added to the roots of healthy sugar beet seedlings, but not when the virus
alone is added. A virus-free isolate of
P. betae acquired the virus when
grown in plants which were infected with the virus by manual inoculation of sap.
The virus seems to be carried internally in the resting spores, because its
infectivity is retained for at least 4 years in air-dried soil
(
Tamada et al., 1975).
Transmission through Seed
Not tested.
Transmission by Dodder
Not tested.
Serology
The virus seems moderately immunogenic. An antiserum against the virus, made
using preparations partially purified by organic solvent clarification and
polyethylene glycol precipitation, had a titre of 1/1024 in ring precipitin tests.
Reactions have also been obtained in agar-gel diffusion tests
(
Tamada & Baba, 1973).
Relationships
The virus is morphologically similar to other viruses with tubular particles,
such as
tobacco mosaic virus.
In many respects, beet necrotic yellow vein virus also
resembles
soil-borne wheat mosaic virus
(
Brakke, 1971) and
potato mop-top virus
(
Harrison, 1974);
these three viruses have particles of two or three predominant
lengths and are transmitted in similar ways by plasmodiophoromycete vectors. No
serological relationship was detected between beet necrotic yellow vein virus and
tobacco mosaic,
tobacco rattle or
soil-borne wheat mosaic viruses
(
Tamada & Baba, 1973).
Stability in Sap
In sugar beet sap, the thermal inactivation point (10 min) is 65 to 70°C
and dilution end-point about 10
-4. Infectivity is retained for 5 days
at 20°C and for 8 days at 4°C. Infectivity of sap extracts is decreased
greatly by freezing
(
Tamada & Baba, 1973).
Purification
No purification procedure has been completely successful, because of
aggregation of the particles. Partially purified virus for serological tests was
obtained using the following procedure
(
Tamada & Baba, 1973).
Grind fresh
leaves of sugar beet in 0.1 M phosphate buffer, pH 7.0, containing 1.0%
2-mercaptoethanol. Clarify the extracts with one-half volume of carbon
tetrachloride and precipitate the virus by adding polyethylene glycol (M.Wt
6000) to 4%. After low-speed centrifugation, clarify the resuspended preparations
with fluorocarbon (Diafron S-3) and then concentrate by further precipitation
with polyethylene glycol, resuspending the virus in a small volume of 0.01 M
phosphate buffer, pH 7.0, or water.
Properties of Particles
No information.
Particle Structure
Particles are straight rods, helically constructed, and have a central canal.
They are about 20 nm wide and of two or three predominant lengths, usually about
390 nm (long particles), about 270 nm (intermediate particles), and 65-105 nm
(short particles)
(
Fig.6).
Isolate CR contains only long and intermediate
particles. The short particles of isolate YS are about 105 nm long, those of
isolate CS about 65 nm, and those of isolate NS about 65 nm and 90 nm long. Each
isolate has more short particles than long and intermediate ones
(
Tamada et al., 1975).
Particle Composition
Not determined.
Relations with Cells and Tissues
The virus is found in the cells of roots, stems and leaves of systemically
infected sugar beet plants. Virus particles are found scattered in the cytoplasm
or in angled-layer aggregates
(
Fig.7).
Virus-like particles are seen in sections
of
P. betae zoospores
(
Fig.9).
Notes
A ‘rhizomania’ disease of sugar beet has been a serious problem in Italy
since the mid 1950s, and is characterized by abnormal proliferation of rootlets
(
Bongiovanni & Lanzoni, 1964;
Ui, 1973).
The disease is quite similar to that
found in Japan
(
Kanzawa & Ui, 1972;
Ui, 1973).
Canova (1966)
suggested that
the Italian disease is caused by mixed infection with
Polymyxa betae and
a virus, and
Faccioli & Giunchedi (1974)
recently isolated a tubular virus
from diseased plants. Characteristics of the virus are very similar to those of
beet necrotic yellow vein virus.
A similar disease has recently been reported in
France
(
Putz & Vuittenez, 1974).
In Japan, rhizomania disease results from
root damage induced by infection with beet necrotic yellow vein virus, and is not
induced by
P. betae, the vector of the virus
(
Tamada et al., 1975;
H. Abe, unpublished data). The virus is usually restricted to the roots of sugar
beet plants grown in infested soil. It is readily detected by examination of
root-dip preparations by electron microscopy
(
Tamada & Baba, 1973).
Symptoms, host range and some properties of beet necrotic yellow vein virus
are quite similar to those of
beet yellow vein virus
(Ruppel & Duffus, 1971).
However, the mode of transmission and particle morphology of the latter virus are
not known.
References
- Bongiovanni & Lanzoni, Progr. agric., Bologna 10: 209, 1964.
- Brakke, CMI/AAB Descriptions of Plant Viruses 77, 4 pp., 1971.
- Canova, Inftore fitopatol. 16: 235, 1966.
- Faccioli & Giunchedi, Phytopath. medit. 13: 10, 1974.
- Harrison, CMI/AAB Descriptions of Plant Viruses 138, 4 pp., 1974.
- Kanzawa & Ui, Ann. phytopath. Soc. Japan 38: 434, 1972.
- Putz & Vuittenez, Annls Phytopath. 6: 129, 1974.
- Ruppel & Duffus, Phytopathology 61: 1418, 1971.
- Tamada & Baba, Ann. phytopath. Soc. Japan 39: 325, 1973.
- Tamada, Kanzawa & Ui, Ann. phytopath. Soc. Japan 36: 365 (abstr.), 1970.
- Tamada, Abe & Baba, Proceedings of the First Intersectional Congress of IAMS, Tokyo, 1974, 3: 313, 1975.
- Ui, Proceedings of Sugar Beet Research, Japan 15: 233, 1973.
Systemically infected plant of sugar beet (YS isolate).
Systemically infected plant of Beta macrocarpa (YS isolate).
Local lesions in inoculated leaves of Tetragonia expansa:
(left) NS isolate, (right) YS isolate.
Local lesions in inoculated leaf of Chenopodium amaranticolor.
Systemically infected leaf of sugar beet (YS isolate).
Virus particles in leaf-dip preparation mounted in 2% phosphotungstate
(YS isolate). Bar represents 100 nm.
Section of infected sugar beet leaf, showing angled-layer aggregates of
virus particles in the cytoplasm. Bar represents 300 nm.
Resting spores of Polymyxa betae within the root cells of sugar beet.
Section of zoospore of P. betae from infected roots, showing
virus-like particles in the cytoplasm. Bar represents 300 nm.
