Rice necrosis mosaic virus
College of Agriculture, University of Osaka Prefecture, Sakai, Osaka, Japan
Okayama Prefectural Agricultural Experiment Station, Sanyo-Cho, Okayama, Japan
Described by Fujii et al. (1966,
A soil-borne virus with slightly flexuous filamentous particles of at least two lengths, c.
275 and 550 nm, and 13-14 nm in width. It is sap-transmissible with difficulty and is transmitted in
soil; the fungus Polymyxa graminis is thought to be a vector. Rice is the only known host.
Found in Japan.
Causes mosaic symptoms in rice (Oryza sativa
) characterized by spindle shaped yellow
flecks and streaks (Fig.1
visible on the lower leaves but usually not on the newly growing leaves.
Causes necrotic fleck lesions on the basal portions of stems and sheaths in some plants
Infected plants are moderately stunted; the tillers are decreased in number, and somewhat prostrate.
Occurs in rice that is transplanted from upland nurseries to paddy fields or direct-seeded in upland
fields; rare in rice transplanted from lowland nurseries to paddy fields or direct-seeded in paddy
Paddy rice with necrosis mosaic disease often suffers also from rice blast
(Pyricularia oryzae) especially on panicles and nodes, resulting in a great reduction of yield
Host Range and Symptomatology
Rice is the only known host. Most of the Japanese paddy rice varieties can be infected by growing
in infective soil. Kanto No. 52 and several other varieties are found to be the most resistant
Other tested species of Gramineae and dicotyledonous plants, including Hordeum vulgare,
Triticum aestivum, Avena sativa, Zea mays, Chenopodium amaranticolor, C. quinoa,
did not develop symptoms when grown in infective soil or after inoculation with infective
sap (Fujii, 1975
; T. Inouye, unpublished data).
- Oryza sativa (rice). Leaf mottling, usually becoming visible on a few lower leaves at the
maximum tillering stage about 70 days after sowing in infective soil, is characterized by spindle
shaped yellow flecks and streaks (Fig.1).
With subsequent growth of the plants, the symptoms spread
successively to the upper leaves, but are usually not visible on the newly produced leaves. Optimum
conditions for virus infection are low soil moisture content and a soil temperature of 25-30°C
- Oryza sativa (rice). The Japanese paddy rice varieties, Akebono, Kibiyoshi, Norin No. 22, or
any others that show symptoms in the field, are suitable.
- No known local lesion host. The virus may be assayed by counting the proportion of rice plants that
No strains reported.
Transmission by VectorsFujii (1975)
suggested that the soil-inhabiting fungus, Polymyxa graminis
), is the
vector of the virus because (1) steamed soil became infective on addition of an extract of rice roots
naturally infected with the virus, (2) P. graminis
was frequently found in the roots of naturally
infected rice, (3) invasion of root hairs of rice seedlings by zoospores of the fungus was observed
on the second day after sowing in infective soil, (4) steamed soil became infective on addition of
resting spores of P. graminis
collected from rice roots naturally infected with the virus, and
the fungus was consistently found in the roots of rice experimentally infected, (5) seedlings grown in
upland rice nurseries had more of the fungus in their roots than did seedlings grown in lowland nurseries.
Transmission through SeedFujikawa et al. (1972)
reported 2.6-5.3% of seeds from infected plants carried the virus,
but Fujii (1975)
found no seed transmission in about 16,000 rice seedlings.
Transmission by Dodder
Serum from a rabbit injected intramuscularly with partially purified virus reacted with the virus
to a titre of 1/80 in micro-precipitin tests (T. Inouye, unpublished data).
Rice necrosis mosaic virus is closely serologically related to
barley yellow mosaic
wheat yellow mosaic viruses
(Usugi & Saito, 1976
It resembles barley yellow mosaic
(Inouye & Saito, 1975
(Hebert & Panizo, 1975
wheat spindle streak mosaic
and wheat yellow mosaic
(Saito et al., 1968
) viruses in its soil transmissibility,
its particle morphology, and in inducing pinwheel-type inclusions and membraneous network structures
in the cytoplasm of infected plant cells.
Stability in Sap
In rice plant sap, the thermal inactivation point is 60-65°C, dilution end point is
1/5000-1/10,000, and longevity in vitro
at room temperature is 7-14 days
(Fujikawa et al., 1970
1. Fujii (1975)
homogenize rice tissue in 6 volumes of 0.2 M phosphate buffer (pH 7.4) containing
0.1% thioglycollic acid and 2% Triton X-100. Add 2 volumes of a 1:1 mixture of chloroform and n
and clarify by low speed centrifugation. Resuspend the pellets from high speed centrifugation in
0.03 M phosphate buffer (pH 7.4). Purify further by sucrose density-gradient centrifugation.
2. T. Inouye (unpublished data): pulverize infected tissue in liquid nitrogen, then add 3 volumes
of 0.05 M borax containing 0.001 M ethylenediamine-tetraacetic acid (EDTA). Express juice through
cheesecloth, clarify by adding 0.2 volume of chloroform and concentrate by 3 cycles of differential
centrifugation. Resuspend the pellets from high speed centrifugation in 0.05 M borate buffer (pH 7.6).
Properties of Particles
are slightly flexuous filaments 13-14 nm in diameter and having at least two
modal lengths (275 and 550 nm) in leaf dip and partially purified preparations
Relations with Cells and Tissues
In cells of epidermal strips from the inside surface of the leaf sheath of infected rice, large
intracellular inclusions (X-bodies) are observed
). In ultrathin sections, characteristic
laminated aggregate inclusions
are observed in the cytoplasm; scattered or loosely
aggregated virus particles are often associated with the laminated aggregates (Fig.7
Membraneous network structures occur in the cytoplasm
) but are less common than the laminated aggregates
Rice necrosis mosaic virus can be readily distinguished from other viruses that infect rice in
Japan by its particle morphology and transmissibility in soils and by inoculation of sap. All the other
viruses are transmitted by leafhoppers but not by sap or through soil;
(Iida et al., 1972
rice black-streaked dwarf
(Yokoyama & Sakai, 1975
Nishi et al., 1975
Doi et al., 1975
viruses have spherical particles, and
rice stripe virus
(Koganezawa et al., 1975
has branched filamentous particles having super-coiled helical structure.
- Doi, Yamashita, Kusunoki, Arai & Yora, Ann. Phytopath. Soc. Japan 41: 228, 1975.
- Fujii, Thesis, Univ. Tokyo, 1975.
- Fujii, Okamoto, Idei & Inouye, Ann. Phytopath. Soc. Japan 32: 325, 1966.
- Fujii, Okamoto, Idei, Shiomi, Inouye, Inouye, Mitsuhata & Asatani, Ann. Phytopath. Soc. Japan 33: 105, 1967.
- Fujikawa, Tomiki & Sato, Nogyo oyobi Engei 45: 1419, 1970.
- Fujikawa, Tomiki & Sato, Ann. Phytopath. Soc. Japan 38: 213, 1972.
- Hebert & Panizo, CMI/AAB Descriptions of Plant Viruses 145, 4 pp., 1975.
- Iida, Shinkai & Kimura, CMI/AAB Descriptions of Plant Viruses 102, 4pp., 1972.
- Inouye, Ann. Phytopath. Soc. Japan 34: 301, 1968.
- Inouye, Nogaku Kenkyu 53: 61, 1969.
- Inouye, Ann. Phytopath. Soc. Japan 36: 186, 1970.
- Inouye & Saito, CMI/AAB Descriptions of Plant Viruses 143, 3 pp., 1975.
- Koganezawa, Doi & Yora, Ann. Phytopath. Soc. Japan 41:148, 1975.
- Nishi, Kimura & Maejima, Ann. Phytopath. Soc. Japan 41: 223, 1975.
- Saito, Tsuchizaki & Hibino, Ann. Phytopath. Soc. Japan 34: 347, 1968.
- Shikata, CMI/AAB Descriptions of Plant Viruses 135, 4 pp., 1974.
- Slykhuis, CMI/AAB Descriptions of Plant Viruses 167, 3 pp., 1976.
- Usugi & Saito, Ann. Phytopath. Soc. Japan 42: 12, 1976.
- Yokoyama & Sakai, Ann. Phytopath. Soc. Japan 41: 219, 1975.
Rice leaves: (left) healthy leaf, (right and centre) leaves showing
Necrosis in the basal portions of stems of infected rice.
X-bodies in epidermal cells of inside surface of leaf sheath of infected rice. (N) nucleus;
Polymyxa graminis in cells of a rice root; (P) plasmodium just about to divide into
resting spores; (R) resting spore cluster; (M) meront.
Virus particles in dip preparation shadowed with chromium. Bar represents 500 nm.
A piece of laminated aggregate inclusion in dip preparation shadowed with chromium. Bar
represents 500 nm.
Section of infected leaf cell showing laminated aggregate inclusions and filamentous virus
particles. Bar represents 500 nm.
Section of infected leaf cell showing membraneous structure. Bar represents 500 nm.