Fauquet, Claude

Lamy, D.

Thouvenel, Jean-Claude

Horizon / Pleins textes

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CMI/AAB Descriptions of Plant Viruses August 1978 No. 190 
GUINEA GRASS MOSAIC VIRUS 
Guinea grass mosaic virus */* : *I6 :E/E : S/*, potyvirus group 
Described by Thouvenel, Givord & Pfeiffer (1976). 
A virus with flexuous, filamentous particles c. 815 nm long. It is readily transmitted by inoculation of 
sap to plants in a few tribes of Gramineae. It is probably restricted to tropical areas in Africa. No 
vector is known. 
MAIN DISEASES: Causes dwarfing and light-green mosaic in Panicuin maximum (Guinea grass) (Fig. 1) 
GEOGRAPHICAL DISTRIBUTION : Widespread wherever Guinea grass is grown in Ivory Coast. 
HOST RANGE AND SYMPTOMATOLOGY: Host range restricted to the Paniceae, Maydeae and 
cultivated as a forage crop. 
Bromeae tribes of the family Gramineae. Mechanically transmissible to the following : 
Diagnostic species 
Panicum maximuni (Guinea grass). General dwarfing and light green mosaic. On some cultivars 
e.g. K189, light green eyespots are the first systemic symptom; later, they anastomose to form 
a striped mosaic (Fig. 2). Other cultivars e.g. K187 seem to be tolerant. 
Setaria italica (Italian ryegrass). Systemic chlorotic elongated spots one week after inoculation, 
Zea mays (maize). Dwarfing; light green mosaic appearing on the new leaves. 
S. italica is a useful host for maintaining cultures. P. maximum cv. K 189 is a good source of virus 
~ followed by mottle. 
Propagation species 
for purification. 
Assay species 
S. italica is a good systemic assay host. No local lesion host is known. 
STRAINS : A strain from maize differs somewhat from Guinea grass strains in host range and is serologi- 
cally distinguishable (D. Lamy, unpublished data). 
TRANSMISSION BY VECTORS : Aphid transmission suspected but not established. No transmission 
to Panicum maximum, Setaria italica or Zea mays was obtained using Rhopalos$hum maidis, Hysteroneura 
setariae, Aphis spiricola or A. gossypii. 
TRANSMISSION THROUGH SEED: Not seed-borne in P. 7naximzim or S. italica. 
TRANSMISSION BY DODDER : Dodder (Cuscuta subinclusa) did not parasitize Guinea grass. 
SEROLOGY: The virus is moderately immunogenic. Rabbit antisera with titres of 1/2 048 were obtained 
after six intramuscular injections of purified virus emulsified with Freund‘s incomplete adjuvant. Micro- 
precipitin tests were used, because intact virus particles do not diffuse in agar gel. 
RELATIONSHIPS : Serologically moderately closely related to pepper veinal mottle virus (Ivory Coast 
and Ghana strains), to dioscorea mosaic virus (Thouvenel & Fauquet, 1977 and unpublished results) and 
a tobacco virus from Kenya (E.1 J. Guthrie, personal comm.). Not related to sugarcane mosaic virus. 
____- 

STABILITY IN SAP: Infectivity in Guinea grass sap is lost after 10 min at 50°C; dilution end-point is 
10 -3. Sap stored at 24°C lost infectivity within a few h; it remained infective at 4°C for 24 h. Frozen 
diseased leaves of Guinea grass remained infective for 2 weeks. 
PURIFICATION: A combination of the methods described by Damirdagh & Shepherd (1970) and Van 
Oosten (1972) is useful. Grind Guinea grass leaves in phosphate buffer (pH 7.5) containing 1~ urea and 
1% sodium bisulphite and clarify by treating with 5% Triton X-100 for 30 min. 
Purified virus is obtained after one cycle of high and low speed centrifugation, followed by ultracentri- 
fugation through 8 ml of 20% sucrose. Finally resuspend the pellet in 0 . 0 5 ~  borate buffer (pH 8.2). 
Preparations can be further purified by centrifuging in 10-40% sucrose density gradients in which the 
virus forms a single light-scattering zone. Infected P. maximum leaves yield c. 25 mg virus per kg. 
Isoelectric point: about pH 4.7; the virus is precipitated at this point (unpublished data). 
A260/A280 : 1.22 & 0.02 (not corrected for light-scattering). 
A max(260)/A min(247): 1.10 f 0.02. 
PARTICLE STRUCTURE: Particles are flexuous filaments about 815 nm long and 15 nm in diameter 
(Fig. 3). After exposure to 0 . 0 5 ~  MgCl, the particles become straighter (Fig. 4), a feature characteristic 
of several viruses in the potyvirus group (Govier ¿? Woods, 1971). 
PROPERTIES OF PARTICLES : 
PARTICLE COMPOSITION: 
Nucleic acid: comprises c. 6% of particle weight (estimated spectrophotometrically). 
Protein: A major protein of M.Wt 35,000, estimated by SDS-polyacrylamide gel electrophoresis, with a 
minor component of M.Wt 32,000 (unpublished results). Probably the second component is a degrada- 
tion product as observed for other potyviruses (Huttinga, 1975). 
RELATIONS WITH CELLS AND TISSUES : No information. 
NOTES : Although no aphid vector has been found, Guinea grass mosaic virus has been classified in the 
potyvirus group on the basis of the size and morphology of its particles and its serological relationship to 
pepper veinal mottle virus and other members of the potyvirus group. 
REFERENCES : Damirdagh & Shepherd, Phytopathology 60: 132, 1970; Govier & Woods, J. gen. Virol. 
13: 127, 1971; Huttinga, Neth.J. Pl. Path. 81: 58,1975; Thouvenel &Fauquet, C.r. hebd. Séanc. Acad. 
Sci., Paris 284: 1947, 1977; Thouvenel, Givord & Pfeiffer, Phytopathology 66: 954, 1976; Van Oosten, 
Neth.J. PI. Path. 78: 33, 1972. 
J.-C. Thouvenel 
C. Fauquet 
D. Lamy 
Laboratoire de Virologie 
B.P. V 51-Abidjan 
Côte d'Ivoire 
ORSTOM-AdiopodoUé 
Fig. 1 
Fig. 3 
Fig. 3 
Fig. 4 
Naturally infected Guinea grass (Paizicum maxiimwz) cv. K 189. 
(Left) Infected leaf of Guinea grass cv. K 189 showing the characteristic mosaic. (Right) Healthy leaf. 
Particles from a purified preparation, negatively stained with 1 % uranyl acetate. Bar represents 200 nm. 
Particles in 0.05 M MgCl,, stained with 1 % uranyl acetate. Bar represents 200 nm. 
Issued jointly by the Commonwealth Mycological Institute, Ferry Lane, Kew, Surrey, England 
and the Association of Applied Biologists. 
0 Commonwealth Agricultural Bureaux and the Association of Applied Biologists, 1978 
Printed by the Cambrian News (Aberystwyth) Ltd., Wales 


Guinea grass mosaic virus

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