Rice tungro virus
G. E. Gálvez
Centro Internacional de Agricultura Tropical, Apartado Aéreo 6713, Cali, Colombia
Anon. (1964) and
Rivera & Ou (1965).
Rice yellow orange leaf virus (Rev. appl. Mycol. 47: 169)
Rice penyakit merah virus (Rev. appl. Mycol. 44: 3043)
Rice leaf yellowing virus (Rev. appl. Mycol. 48: 456)
Rice accep na pula virus (Rev. appl. Mycol. 38: 203)
Rice mentek virus (Rev. appl. Mycol. 45: 112)
A virus with isometric particles c. 30-33 nm in diameter, not transmissible
mechanically but transmitted in a semi-persistent manner by the leafhoppers
Nephotettix impicticeps, N. apicalis and Rocilia dorsalis. It infects a
few species of Gramineae, mainly Oryza spp. It causes the most important virus
diseases of rice in Southeast Asia.
Reported from Philippines, Malaysia, Indonesia, Pakistan, Thailand and India.
Host Range and SymptomatologyOryza
spp. are the main hosts.
found that, of 29 species
of grass weeds tested, the virus produced symptoms in Eleusine indica
infected Echinochloa colonum
and E. crus-galli
symptomlessly. In another
13 of 63 graminaceous species tested were hosts of the virus but
all except Oryza
spp. were poor hosts of the vectors.
Oryza sativa (rice). Symptoms depend on the cultivar. The most commonly used
cultivars are Taichung (Native) 1, and FK 135. Taichung (Native) 1 seedlings show
stunting, with mottling and yellowing of the leaves
FK 135 seedlings show
conspicuous interveinal chlorosis, giving an appearance of yellow stripes with the
S strain, and mottling with the M strain.
Taichung (Native) 1 rice plants 15-20 days after inoculation are suitable sources
of virus for purification.
No local lesion host is known. One-leaf seedlings of the rice cultivar FK 135 show
distinct chlorotic stripes 4-5 days after inoculation.
Two strains, severe (S) and mild (M) have been differentiated by symptoms in the
rice cultivars FK 135 and Achech
Rivera & Ou, 1967
Transmission by Vectors
The main vector is the green leafhopper, Nephotettix impicticeps
The virus is also transmitted by the leafhoppers N. apicalis, N. impicticeps
and Recilia (Inazuma) dorsalis
(Rivera & Ou, 1965
The proportion of insects that transmit the
virus is about 70% for N. impicticeps,
17% for N. apicalis
and 6% for
Gálvez, Shikata & Miah, 1971
five larval stages and adult leafhoppers transmit the virus in the semi-persistent
manner; the proportion of transmitting insects increases with increasing acquisition
access period up to 4 days
There is no latent period. The nymphs cease
to transmit when they moult; all stages lose ability to transmit within 5 days after
the end of an acquisition access period (50% loss after 24 h) and only regain it by
renewed access to virus sources
Biotypes of N.
exist that differ in ability to infest rice cultivars
(Gálvez & Miah, 1969
Transmission through Seed
Transmission by Dodder
The virus is not known to be related to any other virus. The S and M strains
protect against each other in plant-protection tests
(Rivera & Ou, 1967
Stability in Sap
In rice leaf extracts, the virus is stable in phosphate, phosphate-Na2
, Tris, glycine, and ethylenediamine-tetraacetate (EDTA) buffers, all
at 0.01 M, pH 8.0. The concentration of the virus in sap is about 1 mg/l and the
thermal inactivation point (10 min) is about 60°C. The virus becomes denatured
after 1 day at room temperature, 1 week at 4°C, and after 1
month when frozen. These observations on stability were made by photometric scanning
of density gradient columns
Homogenize infected rice leaves with 3 volumes of 0.01 M EDTA, pH 8.0. Filter
and clarify the filtrate by heating at 40°C for 1 hr and centrifuging at 7000
for 20 min. After resuspension in the same 0.01 M EDTA buffer and
centrifugation at 7000 g
for 20 min, the preparation may be further
purified by centrifugation at 73,000 g
for 3 h in sucrose density
gradient columns. The virus, which forms a visible zone, may be collected and
concentrated by a further cycle of differential centrifugation
Properties of Particles
Sedimentation coefficient (s20,w
) at infinite dilution: about
175 S. No accessory viral components are found by analytical centrifugation.
A260/A280: about 1.45 ± 0.06
The particles are isometric with a diameter between 30 and 33 nm
The type of nucleic acid in the particles is unknown, but if it is single-stranded
ratio for the purified virus suggests a nucleic acid content of about
12%; however, this seems rather little for the sedimentation coefficient
Relations with Cells and Tissues
Infected cells sometimes contain dense granules and the chloroplasts and other
cell components degenerate. Virus particles are found in the dense area of
(Gálvez, Shikata & Miah, 1971
The symptoms of rice tungro disease are similar to those of the rice transitory
yellowing disease found in Taiwan, which is transmitted by the leafhoppers
and N. cincticeps,
but this virus has bacilliform
particles and persists in vector leafhoppers for life.
- Anon., Rep. int. Rice Res. Inst. 1963: 114, 1964.
- Anon., Rep. int. Rice Res. Inst. 1964: 150, 1965.
- Anon., Rep. int. Rice Res. Inst. 1968: 103, 1969.
- Anon., Rep. int. Rice Res. Inst. 1969: 59, 1970.
- Gálvez, Virology 35: 418, 1968.
- Gálvez & Miah, Int. Rice Commn Newsl. 18: 4, 1969.
- Gálvez, Shikata & Miah, Phytopath. Z. 70: 53, 1971.
- Ling, Phytopathology 56: 1252, 1966.
- Ling, Bull. ent. Res. 58: 393, 1968.
- Ling, in Viruses, Vectors and Vegetation, New York, Inter-science Publishers, p. 255, 1969.
- Ling, J. econ. Ent. 63: 582, 1970.
- Rivera & Ou, Pl. Dis. Reptr 49: 127, 1965.
- Rivera & Ou, Pl. Dis. Reptr 51: 877, 1967.
- Wathanakul, M.S. Thesis, College Agric., Univ. Philippines, 35 pp, 1964.
Yellowing and stunting symptoms in naturally infected rice.
Nephotettix impicticeps, adult insects. Bar represents 1 mm.
(Courtesy of International Rice Research Institute.)
Virus particles from a purified preparation in phosphotungstate. Bar
represents 100 nm.
Virus particles in an affected cell of rice. Bar represents 1 µm.