S U M M A R YCowpea mild mottle virus (CMMV), a previously undescribed virus widespread in cowpeas (Vigna unguiculata) in the Eastern Region of Ghana, was seed-borne in K unguiculata, Phaseolus mlgaris and Glycim max, but was not transmitted by twelve aphid species including Aphis craccivora, A . fabae, Acyrthosiphon pisum and Myzus pusicae. CMMV was transmitted by inoculation of sap to eleven of seventeen members of the Papilionaceae causing very severe diseases in G. max and Arachis hypogaea, and to ten of fifty-one species within five of nineteen other families; it was best propagated in G. max and Nicotiana clevelandii, and assayed in Chenopodium quinoa. Sap from systemically infected G . m m was infective after dilution to 109 but not I O -~, after 10 min at 65 "C but not at 70 "C, or after 4 days at 18 "C or 16 days at 2 "C. Lyophilized sap was infective after 3 years in vacuo.CMMV has straight to slightly flexuous, fragile filamentous particles, c. 13 x 650 n m which, in sap, are occasionally surrounded by a loose external spiral. About 5 mg of purified virus was obtained from I kg of leaf tissue of G . max or N . clevelandii by clarifying leaf extracts in 0.02 M borate buffer (pH 9 -5 ) with chloroform, followed by two or three cycles of differential centrifugation, and density gradient centrifugation. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 5 yo nucleic acid, contained numerous particles without external spirals, which sedimented as a single component with a sedimentation coefficient SO^,,^) of 165 z 4S, and contained a single polypeptide species with a molecular weight of 32 00-33 000.
Cowpea mild mottle virus (CMMV), although thought to be of only local importance when first found in 1973 infecting cowpeas (Vigna unguiculata) in Ghana, has since been shown to have a very extensive geographical distribution and a wide natural host range. It occurs in Africa, Asia, South America and Oceania in tomato (Lycopersicon esculenturri) and a range of leguminous crops including cowpeas, groundnuts (Arachis hypogaea, soybean (Glycine max) and French beans (Phaseolns vulgaris). The virus has physico‐chemical properties resembling those of aphid‐borne carlaviruses; it has filamentous particles ca. 650 nm long which contain a single polypeptide of 31–33 KDa and single‐stranded RNA of 2. 5 × 106. Unlike carlaviruses, however, CMMV is transmitted in a non‐persistent manner by whiteflies (Bemisia tabaci) and the particles occur in vivo in characteristic brush‐like inclusions. It is also seed‐borne in some, but not all, cultivars of cowpea and soybean, but seed‐transmission is probably dependent upon the interaction of genotype, virus strain, time of infection and environmental factors. CMMV is serologically closely related to, and thus probably synonymous with, viruses previously designated groundnut crinkle, Psophocarpus necrotic mosaic, Voandzeia mosaic and tomato pale chlorosis. It is, however, serologically unrelated to 18 recognized carlaviruses; because it is also transmitted by whiteflies and induces the formation of unusual brush‐like inclusions, it is probably best left unclassified or tentatively placed in a sub‐group of the carlavirus group until the taxonomic significance of these features has been fully evaluated.
A bacilliform virus from Dioscorea alata, designated Dioscorea alata bacilliform virus (DaBV), from Barbados and West Africa and from other Dioscorea spp. from West African, Carribean, Asian and South American countries, has been characterized. The virus was transmitted by the mealybug, Planococcus citri and by mechanical transmission of partially purified preparations to several Dioscorea spp. DaBV was serologically related to a distinct bacilliform virus from Dioscorea bulbifera, to one isolate of sugarcane bacilliform badnavirus and two isolates of banana streak badnavirus (BSV) but was not related to another isolate of BSV or to Kalanchoe top spotting or cacao swollen shoot badnaviruses. The coat protein of DaBV was about 56 kDa and the nucleic acid was double‐stranded DNA of about 7.5 kbp, part of which showed distant homology with other badnaviruses. Thus, DaBV is a distinct hitherto uncharacterized badnavirus.
Pepper veinal mottle virus (PVMV), a previously undescribed virus widespread in Capsicumannuum and C. frutescens in the Eastern Region of Ghana, is acquired and inoculated in 2 min feeding periods by aphids (Myxuspersicae and Aphisgossypii); it is transmissible by inoculation of sap to eleven of fifteen Solanaceae and to five of forty-six other species within three of seventeen other families. The virus was propagated in Nicotiana clevelandii and Petunia hybrida, and assayed in Chenopodium quinoa, C. amaranticolor and C. murale. Sap from Capsicum annuum was infective after dilution to I O -~ but not I O -~, after 10 min at 55 but not 60 "C, and after 7 but not 8 days at 25 "C. Lyophilized sap from P. hybrida was infective after 6 years in vacuo.Yields of 10-25 mg of virus per kg of leaf tissue were consistently obtained from P . hybrida or N . clevelandii by extracting systemically infected leaves in 0.5 M borate (pH 7.8) containing 0.2 % mercaptoethanol and chloroform, followed by repeated precipitation with 50 g polyethylene glycol (M.w. 6000) per 1, several cycles of differential centrifugation and centrifugation in sucrose density-gradient columns. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 6 yo nuclei acid (A 2601280 = 1.25; A 260/246 = 1.27) and contained numerous unaggregated and unbroken filamentous particles c. 770 x 12 nm which sedimented as a single component with a sedimentation coefficient (s&~) of 155 S. PVMV contained RNA (moles yo: G = 24, A = 23, C = 27, U = 26), and a single protein species with a molecular weight of ~2 o o c -~~o o o daltons. PVMV was not serologically related to potato virus Y (three strains), or to twelve other morphologically similar viruses, and seems to be a distinct member of the potato virus Y group. A previously undescribed virus, which we call pepper veinal mottle virus (PVMV), is prevalent in Capsicum annuum L. and C. frutescens L. in the Eastern Region of Ghana. We here describe the main properties of PVMV, a new member of the potato 236 A. A. BRUNT AND R. H. KENTEN virus Y group (Brandes, I 964), and a purification procedure consistently yielding 10-25 mg of virus/kg of leaf.
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