Cowpea aphid-borne mosaic virus
K. R. Bock
Overseas Development Administration, Crop Virology Project, EAAFRO, Nairobi, Kenya
Laboratorio di Fitovirologia Applicata, Consiglio Nazionale delle Ricerche, Turin, Italy
- Described by Lovisolo & Conti (1966) and Bock (1973).
- Synonyms (see also under Relationships)
- Cowpea common mosaic virus (Rev. appl. Mycol. 48: 2838)
- Cowpea mosaic virus (in part) (Rev. appl. Mycol. 20: 444;
26: 524). This name is now used for the isometric virus that is the
type member of the comovirus group - see Van Kammen (1971)
- A distinctive virus with flexuous filamentous particles c. 750 nm
long. It is seed-borne in cowpea, has a wide experimental host range, is
transmitted by several common species of aphid, and occurs in many countries
where cowpea is grown.
Causes a severe mosaic of cowpea (Vigna unguiculata
), the severity
depending on host cultivar and virus strain. Diseased cowpea plants show variable
amounts of dark green vein banding or interveinal chlorosis, leaf distortion,
blistering and stunting (Fig.1
). Viruses that may be related cause mosaic
diseases of adzuki bean (Phaseolus angularis
) and asparagus bean (V.
Occurs in Africa (Kenya, Uganda and Nigeria), Europe (Italy, and probably
Rumania), and Asia (India, Iran, Japan, and probably China). Viruses that are
probably related occur in the USA (Florida) and in the south-west Pacific area.
Host Range and Symptomatology
Infects many species in the Leguminosae and most strains also infect members of
the Amaranthaceae, Chenopodiaceae, Cucurbitaceae, Labiatae and Solanaceae (Lovisolo
& Conti, 1966
; Bos, 1970
; Bock, 1973
- Diagnostic species
- Chenopodium amaranticolor. Local chlorotic or necrotic lesions (Fig.5);
- Glycine max (soybean). Mild systemic mottle with more or less pronounced
- Ocimum basilicum (basil). Local necrotic lesions with whitish centres
(Fig.7); not systemic.
- Petunia hybrida. Systemic infection, either symptomless or with dark
green patches surrounding mid-ribs of leaves.
- Phaseolus vulgaris (French bean). Local chlorotic or necrotic lesions
which spread along the veins (Fig.6). Normally restricted to inoculated leaves
(in cvs. The Prince, Canadian Wonder, Saxa, Scotia) but systemic infection may
follow in cv. Bataaf (European (type) strain; Bos, 1970) or in cv. The Prince
(African mild strain; Bock, 1973).
- Pisum sativum (pea). Systemic mottle in many cvs. (Onward, Greenfeast,
Koroza), but symptomless systemic infection in others (Laxton).
- Propagation species
- Cultures are best maintained in cowpea, soybean or petunia. The virus should
be propagated in cowpea for virus purification; soybean is unsatisfactory for
- Assay species
- Chenopodium amaranticolor is a good local lesion host.
1. European (type) strain
(Lovisolo & Conti, 1966
). Causes a severe
distorting mosaic in cowpea (Fig.1
2. African (neo-type) strain (Bock, 1973). Closely resembles the European
strain in symptom expression. In cowpea cv. Mak 1, induces irregular angular
broken mosaic (Fig.2).
3. African mild strain (Bock, 1973). In cowpea cv. Mak 1, induces a very
mild mottle, with little or no effect on growth of the plants.
4. African veinbanding strain (Bock, 1973). In cowpea cv. Mak 1, induces a
broad dark-green veinbanding (Fig.3).
Transmission by Vectors
The virus is transmitted in the stylet-borne, non-persistent manner by Aphis
), A. fabae, A. gossypii, A. medicaginis, Macrosiphum
and Myzus persicae
(Vidano & Conti, 1965
aphids can retain infectivity up to 15 h after virus acquisition (M. Conti,
Transmission through Seed
Seed transmission is usually slight (0-3 %) but instances of 21.5% have been
recorded in cowpea cv. Kurodane 16 for a virus which resembles the type strain and
14.7% for a virus which may be related, adzuki bean mosaic
(Tsuchizaki, Yora &
). Seed transmission ranged from 3 to 19% in cv. Pusa Phalguni
for an Indian isolate serologically related to the African (neo-type) virus (H. C.
Phatak, personal communication). Plants infected through the seed show bright
mosaic symptoms in primary leaves (Fig.4
Transmission by Dodder
The virus is moderately to strongly immunogenic; an antiserum with a tube
precipitin titre of 1/8192 has been obtained (Bock, 1973
Among the African strains, the neo-type and mild strains are serologically
identical but the veinbanding strain is distinguishable although related. No
serological tests have been made between the African isolates and the European type
strain but they are considered to be strains of the same virus because both are
distantly serologically related to bean common mosaic virus
(Lovisolo & Conti,
: Bock, 1973
) and they resemble one another in particle size and morphology,
physical properties, host range and symptomatology, and in transmission by aphids.
Although cowpea aphid-borne mosaic virus belongs to the potyvirus group
, no direct
serological relationship was detected between the African neo-type strain and
potato virus Y
, bean yellow mosaic
, pea seed-borne mosaic
, clover yellow vein
, sugarcane mosaic
, tobacco severe etch
or iris mosaic
In symptomatology, properties in vitro, and transmission by aphids and
through seed, cowpea aphid-borne mosaic virus resembles the cowpea mosaic
viruses of McLean (1941), Yu (1946), Van Velsen (1962) and Quantz (see Brandes,
1964), the asparagus bean mosaic virus of Snyder (1942) and Hino (1960), and the
Blackeye cowpea mosaic virus of Anderson (1955). It may be related to or
synonymous with some or all of these.
Another virus that is possibly related is adzuki bean mosaic virus, which occurs
in Japan (Hino, 1962) and is apparently confined to species in the Leguminosae.
No serological comparisons have been made but it protects adzuki bean plants
against infection with cowpea aphid-borne mosaic virus (Tsuchizaki et al.,
Stability in Sap
Isolates differ somewhat in stability, but in cowpea sap the thermal inactivation
point lies between 57°C and 60°C, the dilution end-point is between 10-3
and infectivity is retained at 20°C for 1-3 days. Frozen
infected leaves retain infectivity for at least 7 weeks (Bock, 1973
; Lovisolo &
. Homogenize systemically infected cowpea leaves in 0.5 M sodium
citrate buffer containing 1% 2-mercapto-ethanol pH 8.1 (2 ml buffer/1g tissue),
clarify by treatment with 8.5 ml n
-butanol/100 ml sap for 45 min centrifuge
differentially; resuspend in 0.01 M phosphate buffer pH 7.7.
Properties of Particles
Sedimentation coefficient (s
): 150 S for
Particles are flexuous filaments c
. 750 nm long (Fig.8
& Conti, 1966
; Bock, 1973
Relations with Cells and Tissues
The virus induces numerous granular inclusions in epidermal cells of pea but
few in petunia (Bos, 1970
). The virus infects most parts of cowpea plants, including
pollen, anthers and ovaries (Tsuchizaki et al., 1970b
) and embryos
(H. C. Phatak, personal communication).
Several viruses induce mosaic symptoms in cowpea in the field; although vector
type and biophysical properties are useful in diagnosis, particle morphology and
serology are usually necessary for unequivocal identification.
Both cowpea mosaic (Van Kammen, 1971) and cowpea chlorotic mottle (Bancroft,
1971) viruses are readily distinguishable from cowpea aphid-borne mosaic virus
by their isometric particles and transmission by leaf beetles. Cowpea mild mottle
virus (Brunt & Kenten, 1973) has 650 nm filamentous particles and, unlike
cowpea aphid-borne mosaic virus, apparently is not transmitted by aphids.
The cowpea strains of tobacco mosaic (Lister & Thresh, 1955) and southern
bean mosaic (Shepherd & Fulton, 1962) viruses both survive temperatures in
plant sap greatly in excess (more than 20°C) of that which inactivates cowpea
aphid-borne mosaic virus. Although the cowpea strain of bean yellow mosaic virus
(Brierley & Smith, 1962) is best distinguished from cowpea aphid-borne mosaic
virus serologically, it induces severe systemic yellow spotting in Chenopodium
amaranticolor in contrast to the known strains of cowpea aphid-borne mosaic
virus, which do not invade this host systemically.
- Anderson, Pl. Dis. Reptr 39: 349, 1955.
- Bancroft, CMI/AAB Descriptions of Plant Viruses 49, 4 pp., 1971.
- Bock, Ann. appl. Biol. 74: 75, 1973.
- Bos, Neth. J. Pl. Path. 76: 8, 1970.
- Brandes, Mitt. biol. BundAnst. Ld.- u. Forstw. 110, 130 pp., 1964.
- Brierley & Smith, Pl. Dis. Reptr 46: 335, 1962.
- Brunt & Kenten, Ann. appl. Biol. 74: 67, 1973.
- Hino, Ann. phytopath. Soc. Japan 25: 178, 1960.
- Hino, Ann. phytopath. Soc. Japan 27: 138, 1962.
- Lister & Thresh, Nature, Lond. 175: 1047, 1955.
- Lovisolo & Conti, Neth. J. Pl. Path. 72: 265, 1966.
- McLean, Phytopathology 31: 420, 1941.
- Shepherd & Fulton, Phytopathology 52: 489, 1962.
- Snyder, Phytopathology 32: 518, 1942.
- Tsuchizaki, Yora & Asuyama, Ann. phytopath. Soc. Japan 36: 112, 1970a.
- Tsuchizaki, Yora & Asuyama, Ann. phytopath. Soc. Japan 36: 237, 1970b.
- Van Kammen, CMI/AAB Descriptions of Plant Viruses 47, 4 pp., 1971.
- Van Velsen, Papua New Guin. agric. J. 14: 153, 1962.
- Vidano & Conti, Atti. Accad. Sci. Torino 99: 1041, 1965.
- Yu, Ann. appl. Biol. 33: 450, 1946.
Symptoms induced in cowpea by European (type) strain (chronic infection).
Symptoms induced in cowpea by African (neo-type) strain.
Symptoms induced in cowpea by African veinbanding strain.
Mosaic symptoms in primary leaves of cowpea infected through the seed by
European (type) strain.
Local lesions induced in Chenopodium amaranticolor by European
Local lesions induced in Phaseolus vulgaris by European (type)
Local necrotic lesions induced in Ocimum basilicum by European
Virus particles from a purified preparation of African (neo-type) strain
in phosphotungstate. Bar represents 200 nm.