Mung bean yellow mosaic virus
National Agriculture Research Center, Yatabe, Tsukuba, Ibaraki 305, Japan
NODAl Research Institute, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156, Japan
- Disease first described by Nariani (1960). Virus particles first observed by
Thongmeearkom et al. (1981a) and purified by Honda et al.
- A virus with geminate particles, c. 30 x 18 nm, containing two species
of circular single-stranded DNA. The host range is largely confined to species of
Leguminosae. The virus is transmitted by the whitefly, Bemisia tabaci, in
the persistent (circulative) manner, and by inoculation with sap. The virus causes
serious losses of yield in mung bean and blackgram.
Causes a yellow mosaic disease of mung bean (Vigna radiata
) starting as
small yellow specks along the veinlets and spreading over the lamina; the pods
become thin and curl upward (Fig.1
). In blackgram (Vigna mungo
) there are
two types of yellow mosaic symptom depending upon the variety: yellow mottle
(generalized yellowing of the leaves) and necrotic mottle (yellowing restricted
to small spots which turn necrotic) (Nene, 1973
; Nair et al., 1974
India the virus causes more severe yellow mosaic disease in blackgram than in mung
bean (Williams et al., 1968
); however, in Thailand the disease is common in
mung bean but is seldom observed in blackgram under natural conditions (Honda
et al., 1983
Distributed in south Asia. Reported from India (Nariani, 1960
), West Pakistan
(Ahmad & Harwood, 1973
), Sri Lanka (Shivanathan, 1977
) and Thailand
(Thongmeearkom et al., 1981b
Host Range and Symptomatology
The virus from Thailand has been transmitted by mechanical inoculation, but
only to Canavalia ensiformis, Glycine max, Phaseolus angularis, P. lunatus,
P. vulgaris, Vigna mungo
and V. radiata,
all of which are members of
the Leguminosae (Honda et al., 1983
). The virus reported from India has not
been transmitted by mechanical inoculation but has been transmitted by the
whitefly vector, not only to several species in the Leguminosae (Nariani, 1960
but also to Brachiaria romosa
(Gramineae) and Cosmos bipinnatus,
and Xanthium strumarium
(Compositae) (Nene et al.,
; Nene, 1973
; Rathi & Nene, 1974
- Diagnostic species
- Glycine max (soybean). Small yellow specks along the veinlets developing
into yellow mosaic.
- Phaseolus vulgaris (French bean). Young systemically infected
leaflets show downward curling without yellow mosaic (Fig.4). Irregular
chlorotic spots develop rarely.
- Vigna radiata (mung bean). Irregular chlorotic spots along the
veinlets developing into yellow mosaic (Fig.2, Fig.3). The first emerging
trifoliolate leaves often show severe downward curling.
- Propagation species
- Phaseolus vulgaris cv. Top Crop grown at about 30°C in high
humidity is a good source of virus for purification. Systemically infected
leaves are harvested within 2 weeks after mechanical inoculation.
- Assay species
- No local lesion host is known. Infectivity of purified virus preparations
may be assayed by determining the proportion of young seedlings of Vigna
radiata that become infected following mechanical inoculation. A similar
whole plant assay in V. radiata is used to measure the frequency of
transmission by whitefly vectors.
Host range, symptomatology and mechanical transmission suggest that there
may be relationships among the isolates of mung bean yellow mosaic virus from
India, West Pakistan, Sri Lanka and Thailand. The Thai isolate of the virus is
transmissible by mechanical inoculation and its host range appears to be
restricted to seven species in the Leguminosae (Honda et al., 1983
the contrary, other isolates from India, West Pakistan and Sri Lanka are not
sap-transmissible (Nene, 1972
; Ahmad & Harwood, 1973
; Shivanathan, 1977
Indian isolate had a wider host range than Thai isolates including certain
species in the Leguminosae, Compositae and Gramineae (Nene, 1972
serological relationships among these presumed isolates of mung bean yellow
mosaic virus from various countries are not yet understood.
Transmission by Vectors
Transmissible by the whitefly, Bemisia tabaci
& Harwood, 1973
; Shivanathan, 1977
; Thongmeearkom et al.,
). Acquisition and inoculation by adults can each be effected in a
minimum time of 15 min. The latent period is less than 4 h (Nair, 1971
single viruliferous adult can transmit the virus. The most efficient female and
male adults in a population can retain infectivity for 10 days and 3 days,
respectively. Neither female nor male adults can retain infectivity throughout
the life span. Female adults are over three times more efficient as vectors than
males (Rathi, 1972
). Nymphs of Bemisia tabaci
can acquire the virus from
diseased leaves (Nene, 1972
). The virus does not pass through eggs of
; Ahmad & Harwood, 1973
Transmission through Seed
Not seed-transmitted in mung bean or soybean (Y. Honda, unpublished data).
An antiserum against the Thai isolate had titres of 1/160 in the tube
precipitin test and at least 1/409,600 in a Western immunoblotting technique
and dot immunobinding assay (Honda, 1986
Serological relationships are found between mung bean yellow mosaic virus
and bean golden mosaic
virus by Ouchterlony double diffusion tests (M. Ikegami,
unpublished data), dot immunobinding assay and Western immunoblotting (Honda,
), although the host range and symptomatology of the two viruses are
different (Honda et al., 1983
Both viruses react in the Western
immunoblotting technique with antisera against other whitefly-transmitted
geminiviruses, including African cassava mosaic
, tobacco leaf curl
and tomato yellow leaf curl viruses (Y. Honda, unpublished data). In Ouchterlony double
diffusion tests, mung bean yellow mosaic virus forms a single band of precipitate
with antiserum against African cassava mosaic virus (Y. Honda & M. Ikegami,
unpublished data), and a relationship between the two viruses can also be shown
by immunosorbent electron microscopy (I. M. Roberts & B. D. Harrison,
Stability in Sap
In infected Vigna radiata
sap, the thermal inactivation point
(10 min) is 40-50°C, the dilution end-point is between
, and the longevity in vitro
is 1-2 days at 20°C
(Honda et al., 1983
). Infectivity is retained for at least 4 years
in frozen dehydrated leaves or frozen leaves (Y. Honda & M. Ikegami,
Homogenize systemically infected leaves in 0.1 M potassium phosphate,
pH 7.8, containing 0.1% thioglycollic acid, 10 mM sodium
diethyldithiocarbamate and 1 mM sodium ethylenediamine-tetraacetate (2 ml/g
tissue). Clarify by adding 0.5 vol. chloroform and centrifuging at low speed.
Add NaCl to 0.2 M and polyethylene glycol (PEG), M. Wt 6000, to 6% (w/v) and
centrifuge at 15,000 g
for 30 min. Dissolve the precipitate in
0.1 M potassium phosphate, pH 7.8. Clarify by low-speed centrifugation, then
centrifuge at 125,000 g
for 90 min and resuspend the pellets
in potassium phosphate buffer containing 6% PEG and 0.2 M NaCl. Layer the
preparations onto PEG discontinuous reverse solubility gradients (Honda
et al., 1983
), then centrifuge in a Hitachi RPS 25 swinging bucket
rotor at 15,000 g
for 30 min. Recover the opaque band and
concentrate the virus by high-speed centrifugation. Final purification is
by sucrose density gradient centrifugation. Yield is less than 1 mg virus
particles/kg leaf (Honda et al., 1983
Properties of Particles
The geminate particles form a single band in sucrose density gradients
(Honda et al., 1983
A260/A280 : 1.3-1.4.
Particle weight (daltons): 4.0 x 106.
The virus particles are geminate, c.
30 x 18 nm; the protein
shells can perhaps be regarded as formed by the fusion of two quasi-icosahedra
). The particles are stable in 2% sodium phosphotungstate (pH 3.5) or
2% uranyl acetate without any previous fixation (Honda et al., 1983
Particle CompositionNucleic acid:
Circular single-stranded (ss) DNA, about 20% of particle
weight. M. Wt c.
0.8 x 106
, estimated by electron microscopy
Ikegami et al., 1985
) at pH 7.0, i
= 0.1: 16 S
(Ikegami et al., 1985
endonuclease mapping shows that there are two major DNA species of similar size
; Morinaga et al., 1985
DNA-1 has 2715 nucleotides (22.5% G, 27.1% A, 20.7% C, 29.7% T; M. Wt 0.84 x 106
and DNA-2 has 2637 nucleotides (20.6% G, 28.7% A, 19.0% C, 31.7% T; M. Wt 0.81 x 106
(Morinaga et al., 1985
Protein: One species of polypeptide in the particles, of M. Wt c.
27,500, estimated by SDS/polyacrylamide gel electrophoresis (Honda, 1986).
A double-stranded (ds) DNA, probably a replicative intermediate, isolated
from infected leaves of Top Crop bean is a circular molecule and has sequences
complementary to those of viral DNA. Both the dsDNA from leaves and the ssDNA
from virus particles are infective in Top Crop bean when assayed by mechanical
inoculation (Ikegami et al., 1984
). The two genomic DNA species have
different sequences except for a common region of about 200 nucleotides which
is almost identical in the two molecules (Morinaga et al., 1985
common region contains a possible stem-loop structure of 34 nucleotides with
a G + C-rich 11 base-pair stem and an A + T-rich 12-nucleotide loop
(Morinaga et al., 1985
). The loop sequence includes the sequence TAATATTAC.
Relations with Cells and Tissues
In Vigna radiata
leaf cells, the virus particles often form loose
) that sometimes fill almost completely the nuclei of infected
phloem cells. In V. radiata,
hypertrophied nucleoli, aggregates of virus
particles and fibrillar bodies appear in the nuclei of phloem cells as early as
two days before symptom appearance. Virus particles are sometimes scattered in
distribution but they occasionally form aggregates having a paracrystalline or
double cylindrical arrangement in the vacuoles of infected sieve elements
(Thongmeearkom et al., 1981a
Among four viruses presumed to be mung bean yellow mosaic virus,
from India, West Pakistan, Sri Lanka and Thailand, virus purification (Honda
et al., 1983
) and nucleotide sequencing (Morinaga et al., 1985
) have been reported only for the Thai isolate. Comparisons of the sequence
homology among the four viruses could be useful in determining which are
isolates of mung bean yellow mosaic virus and which are separate viruses. The
DNA-1 of mung bean yellow mosaic virus has substantial sequence homology with the
corresponding DNA species of bean golden mosaic virus
but there is relatively
little homology between DNA-2 and the smaller of the two genome species of bean
golden mosaic virus. Also the common regions, except for the stem-loop sequence,
of the two DNA species of mung bean yellow mosaic virus are different in
sequence from those of bean golden mosaic virus (Morinaga et al., 1987
- Ahmad & Harwood, Pl. Dis. Reptr 57: 800, 1973.
- Honda, Ann. phytopath. Soc. Japan 52: 553, 1986.
- Honda, Iwaki, Saito, Thongmeearkom, Kittisak & Deema, Pl. Dis. 67: 801, 1983.
- Ikegami, Morinaga & Miura, Virus Res. 1: 507, 1984.
- Ikegami, Yazaki, Honda, Iwaki, Fujii, Morinaga & Miura, Microbiol. Immunol. 29: 783, 1985.
- Morinaga, Arai, Miura & Ikegami, Abstr. 33rd Meeting Soc. Japanese Virologists, p. 347, 1985.
- Morinaga, Ikegami, Shimotohno & Miura, Microbiol. Immunol. 31: 147, 1987.
- Nair, Ph.D. Thesis, Uttar Pradesh Agricultural University, Pantnagar, India, 1971. In Nene, 1972.
- Nair, Nene & Naresh, Indian Phytopath. 27: 256, 1974.
- Nariani, Indian Phytopath. 13: 24, 1960.
- Nene, A Survey of Viral Diseases of Pulse Crops in Uttar Pradesh, Res. Bull. No. 4, 191 pp., G.B. Pant University of Agriculture & Technology, Pantnagar, India, 1972.
- Nene, Pl. Dis. Reptr 57: 463, 1973.
- Nene, Naresh & Nair, Indian Phytopath. 24: 415, 1971.
- Rathi, Ph.D. Thesis, G.B. Pant University of Agriculture & Technology, Pantnagar, India 1972. In Nene, 1972.
- Rathi & Nene, Indian Phytopath. 27: 429, 1974.
- Shivanathan, Trop. Agric. Res. Ser. (Trop. Agric. Res. Center, Japan), No. 10, p. 65, 1977.
- Thongmeearkom, Honda, Saito & Syamananda, Phytopathology 71: 41, 1981a.
- Thongmeearkom, Kittipakorn & Surin, Thai J. agric. Sci. 14: 201, 1981b.
- Williams, Grewal & Amin, Pl. Dis. Reptr 52: 300, 1968.
Upward curling symptoms of naturally infected Vigna radiata
Irregular chlorotic spots along the veinlets in V. radiata
leaf at an early stage of infection.
Yellow mosaic symptoms in V. radiata leaf at late stage of
Severe downward curling symptoms in Phaseolus vulgaris cv.
Purified virus preparation stained with 2% uranyl acetate.
Bar represents 500 nm.
Ultrathin section of infected V. radiata phloem cell, showing
an aggregate of virus particles (V) in the nucleus. Bar represents 1 µm.
Electron micrograph of mung bean yellow mosaic virus DNA (smaller
molecule) and fX 174 DNA (larger molecule). Bar
represents 500 nm.
Physical map of two genome DNA species of mung bean yellow mosaic
virus (courtesy T. Morinaga).