Recognition and differentiation of seven whitefly-transmitted geminiviruses from India, and their relationships to African cassava mosaic and Thailand mung bean yellow mosaic viruses

Particles resembling those of geminiviruses were found by immunosorbent electron microscopy in extracts of plants infected in India with bhendi yellow vein mosaic, croton yellow vein mosaic, dolichos yellow mosaic, horsegram yellow mosaic, Indian cassava mosaic and tomato leaf curl viruses. All these viruses were transmitted by Bemisia tabaci whiteflies, all reacted with at least one out of ten monoclonal antibodies to African cassava mosaic virus (ACMV), and all reacted with a probe for ACMV DNA-1, but scarcely or not at all with a full-length probe for ACMV DNA-2. Most of the viruses were distinguished by their host ranges when transmitted by whiteflies, and the rest could be distinguished by their pattern of reactions with the panel of monoclonal antibodies. Horsegram yellow mosaic virus was distinguished from Thailand mung bean yellow mosaic virus by its lack of sap transmissibility, ability to infect Arachis hypogaea, failure to react strongly with the probe for ACMV DNA-2 and its pattern of reactions with the monoclonal antibodies. Structures resembling a ‘string of pearls’, but not geminate particles, were found in leaf extracts containing malvastrum yellow vein mosaic virus. Such extracts reacted with two of the monoclonal antibodies, suggesting that this whitefly-transmitted virus too is a geminivirus. All seven viruses from India can therefore be considered whitefly-transmitted geminiviruses.     

Nicotiana velutina mosaic virus: purification, properties and affinities with other rod-shaped viruses

Nicotiana velutina mosaic virus (NVMV), found in Australia, was transmitted by inoculation of sap to twenty species in the Solanaceae and Chenopodiaceae, and to Gomphrena globosa; its host range closely resembles that of potato mop-top virus (PMTV). Infectivity was abolished when sap was kept at room temperature between 1 and 4 days, or when heated for 10 min between 60 and 70 °C. NVMV was frequently transmitted through the seed of four Nicotiana spp. NVMV and PMTV were purified by a method that involved redissolving virus particles sedimented by low speed centrifugation of leaf extracts, followed by sedimentation through sucrose cushions. NVMV preparations contain rod-shaped particles about 18 nm wide and with a large range of lengths, the commonest being 125–150 nm. The particles have a helical structure with a pitch of 2–9 nm, break easily, and contain a single protein of apparent mol. wt. 21|400, slightly larger than that of PMTV (19 800). In serological tests assessed by electron microscopy, no relationship was detected between NVMV and PMTV, or barley stripe mosaic, beet necrotic yellow vein, soil-borne wheat mosaic, tobacco mosaic or tobacco rattle viruses. However, antiserum to soil-borne wheat mosaic virus reacted quite strongly with PMTV and weakly with tobacco mosaic virus. NVMV is considered to be a distinct member of the tobamovirus group; its frequent transmission through seed may be an adaptation to the arid environment where it was found. Its cryptogram is */*:*/*:E/E:S/*.     

Pepino mosaic virus, a new potexvirus from pepino (Solanum muricatum)

Pepino mosaic virus (PepMV), a previously undescribed virus, was found in fields of pepino (Solanum muricatum) in the Canete valley in coastal Peru. PepMV was transmitted by inoculation of sap to 32 species from three families out of 47 species from nine families tested. It caused a yellow mosaic in young leaves of pepino and either a mild mosaic or symptomless infection in 12 wild potato species, five potato cultivars and potato clone USDA 41956 but S. stoloniferum and potato cultivars Merpata and Revolucion reacted with severe systemic necrotic symptoms. The virus was transmitted by plant contact but not by Myzus persicae. It was best propagated and assayed in Nicotiana glutinosa. Sap from infected N. glutinosa was infective after dilution to 10^-1 but not 10^-6, after 10 min at 65°C but not 70°C and after 3 months at 20°C. PepMV had filamentous particles with a normal length of 508 nm; the ends of some seemed damaged. Ultra-thin sections of infected leaves of N. glutinosa revealed many inclusions containing arrays of virus-like particles some of which were banded or whorled; small aggregates of virus-like particles were also common. The virus was purified by extracting sap from infected leaves in a solution containing 0·065 M disodium tetraborate, 0·435 M boric acid, 0·2% ascorbic acid and 0·2% sodium sulphite at pH 7·8, adding silver nitrate solution to the extract, and precipitating the virus with polyethylene glycol followed by two cycles of differential centrifugation. Particles of PepMV normally yielded two proteins with molecular weights of 26 600 and 23 200, but virus obtained from infective sap aged overnight yielded only the smaller protein suggesting that it was a product of degradation of the larger one. The virus is serologically related to two potexviruses, narcissus mosaic and cactus X and its properties are typical of the potexvirus group.     

Narcissus mosaic virus

Narcissus mosaic virus (NMV) is widespread in British crops of trumpet, large-cupped and double daffodils, but was not found in Narcissus jonquilla or N. tazzeta. Many commercial daffodil cultivars seem totally infected, and roguing or selection is therefore impracticable. Strict precautions by breeders and raisers to prevent infection of new cultivars is recommended. Healthy daffodil seedlings were readily infected with NMV by mechanical inoculation, but the virus was not detected in them until 17 months after inoculation, when a mild mosaic appeared. NMV infected twenty-eight of fifty-three inoculated plant species; only five (Nicotiana clevelandii, Gomphrena globosa, Medicago sativa, Trifolium campestre and T. incarnatum) were infected systemically, and NMV was cultured in these and assayed in Chenopodium amaranticolor and Tetragonia expansa. The virus was not transmitted to and from G. globosa or N. clevelandii by three aphid species, or through the seeds of Narcissus, G. globosa and N. clevelandii but was transmitted by handling. G. globosa sap was infective at a dilution of 10 ^-5 but not at 10^-6, when heated for 10 min. at 70° C. but not at 75° C, and after 12 weeks at 18° C, or 36 weeks at 0–4° C. NMV withstood freezing in infected leaves and sap, and purified preparations and freeze-dried sap remained infective for over 2 years. NMV was precipitated without inactivation by ammonium sulphate (313 g./l.) but was better purified by differential centrifugation of phosphate-buffer extracts treated with n-butanol. Such virus preparations from G. globosa, N. clevelandii, C. amaranticolor and T. expansa were highly infective, serologically active, produced a specific light-scattering zone when centrifuged in density-gradients and contained numerous unaggregated particles with a commonest length of 548–568 mμ. Antisera prepared in rabbits had precipitin tube titres of 1/4096. NMV was detected in three experimental hosts but not in narcissus sap. Unlike some viruses with elongated particles, NMV precipitates with antiserum in agar-gel. Purified preparations reacted with antiserum to a Dutch isolate of NMV but not with antisera to seven other viruses having similar particles and in vitro properties, or to narcissus yellow stripe virus.     

East African strains of cowpea aphid-borne mosaic virus

Cowpea aphid-borne mosaic virus (CAMV) was isolated for the first time in East Africa where three distinct strains, type, veinbanding and mild, were differentiated by host range and serology. The three strains infected 17/38, 18/37 and 10/35 legume species, and 11/21, 7/21 and 3/19 non-legume species, respectively. The viruses were propagated in cowpea and assayed in Chenopodium amaranticolor. Isolates of all three strains had similar in vitro properties: dilution end point between 10^-3 and 10^-4; thermal inactivation point between 56 and 58 °C; longevity in vitro between 2 and 3 days. Infectivity of sap from frozen leaves was high after 4 wk but much less after 7 wk; infectivity was largely precipitated by 50% acetone but inactivated by 50% ethanol. High yields of virus were consistently obtained from cowpea by extracting systemically infected leaves in 0.5 m sodium citrate containing 1% mercaptoethanol (pH 8.1), and clarifying with 8.5 ml n-butanol/100 ml sap. Virus preparations contained numerous unaggregated and aggregated virus particles c. 750 nm long and contained components with sedimentation coefficients (s°_{20, w}) of 150S and 175S (presumably unaggregated and aggregated particles, respectively). CAMV is serologically distantly related to bean common mosaic virus, but not to bean yellow mosaic or eight other morphologically similar viruses. It is a typical but distinct member of the potato virus Y group.     

Involvement of Volatile Substances in Systemic Resistance of Barley Against Erysiphe graminis f. sp. hordei Induced by Pruning of Leaves

Horsegram yellow mosaic disease was shown to be caused by a geminivirus; horsegram yellow mosaic virus (HYMV). The virus could not be transmitted by mechanical sap inoculation. Leaf dip and purified virus preparations showed geminate virus particles, measuring 15-18 * 30 nm. An antiserum for HYMV was produced and in enzyme-linked immunosorbent assay (ELISA) and immunosorbent electron microscopy (ISEM) tests HYMV was detected in leaf extracts of fieldinfected bambara groundnut, french bean, groundnut, limabean, mungbean, pigeonpea and soybean showing yellow mosaic symptoms. Bemisia tabaci fed on purified HYMV through a parafilm membrane transmitted the virus to all the hosts listed above but not to Ageratum conyzoides, okra, cassava, cowpea, Croton bonplandianus, Lab-lab purpureus, Malvastrum coromandalianum and tomato. No reaction was obtained in ELISA and ISEM tests between HYMV antibodies and extracts of plants diseased by whitefly-transmitted agents in India such as A. conyzoides yellow mosaic, okra yellow vein mosaic, C. bonplandianus, yellow vein mosaic, M. coromandalianum yellow vein mosaic, tomato leaf curl and cassava mosaic. HYMV was also not found to be related serologically to bean golden mosaic, virus.     

Purification and Characterization of Indian Cassava Mosaic Virus

The Indian cassava mosaic virus (ICMV) was transmitted by the whitefly Bemisia tabaci and sap inoculation. ICMV was purified from cassava and from systemically infected Nicotiana benthamiana leaves. Geminate particles of 16–18 × 30 nm in size were observed by electron microscopy. The particles contained a single major protein of an estimated molecular weight of 34,000. Specific antiserum trapped geminate particles from the extracts of infected cassava and N. benthamiana plants in ISEM test. The virus was detected in crude extracts of infected cassava, ceara rubber, TV. benthamiana and N. tabacum cv. Jayasri plants by ELISA. ICMV appeared serologically related to the gemini viruses of Acalypha yellow mosaic, bhendi yellow vein mosaic, Croton yellow vein mosaic, Dolichos yellow mosaic, horsegram yellow mosaic, Malvastrum yellow vein mosaic and tobacco leaf curl.     

Czech and scandinavian isolates resembling dandelion yellow mosaic virus

Virus isolates resembling the dandelion yellow mosaic virus (synonym: lettuce necrosis virus) were obtained from dandelion plants in twenty five localities of Bohemia and also of Norway, Sweden and Finland. All isolates were sap transmissible merely to lettuce, but some of them also toChenopodium quinoa; other test plants could not be infected. Attempted serological and biological identification of the isolates with some viruses presumed to be able to infect spontaneously dandelion plants have failed.     

Occurrence of grapevine chrome mosaic nepovirus in Austria

A virus recovered by inoculation of sap from Austrian vines with yellow mosaic symptoms was compared with, and found virtually indistinguishable from, an authentic Hungarian isolate of grapevine chrome mosaic nepovirus. This seems to be the first record of the virus in Austria.     

Occurence of grapevine chrome mosaic nepovirus in Austria

A virus recovered by inoculation of sap from Austrian vines with yellow mosaic symptoms was compared with, and found virtually indistinguishable from, an authentic Hungarian isolate of grapevine chrome mosaic nepovirus. This seems to be the first record of the virus in Austria.     

Eggplant mosaic virus, and its relationship to Andean potato latent virus

Eggplant mosaic virus (EMV), obtained from Solanum melongena L. from Trinidad, is readily transmitted by inoculation of sap to several solanaceous and a few non-solanaceous plant species. Purified preparations of EMV contain isometric particles 30 nm in diameter, and with sedimentation co efficients of either 111 or 53 S. The particles have thirty-two major morphological subunits. EMV is closely serologically related to Andean potato latent virus and has a similar host range, but is more virulent. Also, whereas EMV accumulates fastest in Nicotiana clevelandii leaves at 20–24 °C, Andean potato latent virus accumulates fastest at 15 °C, and fails to attain a serologically detectable concentration at 24 °C. A few symptomatologically or serologically distinguishable strains of EMV were obtained. EMV has properties typical of viruses of the Andean potato latent subgroup of the turnip yellow mosaic group of viruses, and its present cryptogram is */*:*/*:S/S:S/Cl.     

A yellow mosaic disease of horse chestnut (Aesculus spp.) caused by apple mosaic virus

A severe foliar yellow mosaic disease was observed in horse chestnut trees (Aesculus carnea and A. hippocastanum). Reactions in woody indicator plants grafted with diseased horse chestnut suggested the presence of an ilarvirus. Virus isolates obtained by mechanical inoculation of herbaceous test plants reacted with antisera to apple mosaic virus but not with antisera to its serotype prunus necrotic ringspot virus, or to prune dwarf virus. Yellow mosaic was induced in horse chestnut seedlings grafted with tissues from herbaceous hosts infected with horse chestnut isolates or with the European plum line pattern isolate of apple mosaic virus. Virus was detected by enzyme-linked immunosorbent assay (ELISA) in embryo and endosperm of immature seed from infected trees but not in mature seed, or progeny seedlings. Strawberry latent ringspot virus was detected in one of six A. hippocastanum trees with a leaf vein yellows disease.     

Cytopathology of Plgeonpea sterility mosaic virus in pigeonpea and Nicotiana benthamiana: similarities with those of eriophyid mite-borne agents of undefined aetiology

Pigeonpea sterility mosaic virus (PPSMV) is transmitted by the eriophyid mite, Aceria cajani, and is very closely associated with sterility mosaic disease (SMD) of pigeonpea (Cajanus cajah) in the Indian subcontinent. Antiserum produced to purified PPSMV preparations detected a virus‐specific 32 kDa protein in sap of SMD‐affected pigeonpea plants by ELISA and Western blotting. PPSMV was transmitted mechanically in sap of SMD‐affected pigeonpea leaves to Nicotiana benthamiana. Ultrastructural studies of symptom‐bearing leaves of two pigeonpea cultivars, (ICP8863 and ICP2376) and N. benthamiana infected with PPSMV, detected quasi‐spherical, membrane bound bodies (MBBs) of c. 100–150 nm and amorphous electron‐dense material (EDM). These structures were distributed singly or in groups, in the cytoplasm of all cells, except those in conductive tissues. Fibrous inclusions (FIs), composed of randomly dispersed fibrils with electron lucent areas, were present in the cytoplasm of palisade cells and rarely in mesophyll cells of the two pigeonpea cultivars but were not detected in infected TV. benthamiana plants. In the PPSMV‐infected pigeonpea cultivars and TV. benthamiana, immuno‐gold labelling, using antiserum to PPSMV, specifically labelled the MBBs and associated EDM, but not the FIs. The MBBs and associated inclusions are similar in appearance to those reported for plants infected with the eriophyid mite‐transmitted High Plains virus and the agents of unidentified aetiology associated with rose rosette, fig mosaic, thistle mosaic, wheat spot chlorosis and yellow ringspot of budwood. The nature of these different inclusions is discussed.     

Arabis mosaic and Prunus necrotic ringspot viruses in hop (Humulus lupulus L.)

Purified virus preparations made from nettlehead-diseased hop plants, or from Chenopodium quinoa, to which the virus was transmitted by inoculation of sap, contained polyhedral virus particles of 30 mμ diameter which were identified serologically as arabis mosaic virus (AMV). There were serological differences between AMV isolates from hop and from strawberry, and also differences in host range and in symptoms caused in C. quinoa and C. amaranticolor. AMV was always associated with nettlehead disease. The nematode Xiphinema diversicaudatum occurred in small numbers in most hop gardens, but was numerous where nettlehead disease was spreading rapidly. Preparations from nettlehead-affected hops also contained a second virus, serologically related to Prunus necrotic ringspot virus (NRSV), in mild and virulent forms which infected the same range of test plants but showed some serological differences. Mild isolates did not protect C. quinoa plants against infection by virulent isolates. Hop seedlings inoculated with virulent isolates of NRSV developed symptoms indistinguishable from those of split leaf blotch disease. Latent infection with NRSV was prevalent in symptomless hop plants. Nettlehead disease is apparently associated with dual infection of AMV and virulent isolates of NRSV. An unnamed virus with rod-shaped particles 650 mμ long was common in hop and was transmitted by inoculation of sap to herbaceous plants. Cucumber mosaic virus was obtained from a single plant of Humulus scandens Merr.     

Purification and properties of arabis mosaic and tomato bushy stunt viruses isolated from lilac (Syringa vulgaris L.)

The paper gives more detailed characteristics of Arabis mosaic virus (AMV) and tomato bushy stunt virus (TBSV) isolated from lilac, the latter being identified in lilac (from plants suffering from yellow ring disease) for the first time. The isolate of TBSV from lilac, from which an antiserum with a titre of 1024 was prepared, is closely related to the artichoke strain. Information is given about two types of ringspot disease and about chlorotic ringspot of lilac. Whereas in the leaves of lilac suffering from ringspot disease (of ring mosaic type) the presence of AMV was demonstrated, the sap transmission from the leaves diseased with ringspot of linepattern (and wave-like mosaic) type failed; from the leaves affected by chlorotic ringspot a mixture of AMV and cherry leaf roll virus was identified. In addition, the polyetiological nature of “spring” mosaic and necrotic mosaic of lilac, in which bacteriumPseudomonas syringae van Hall, was found is dealt with. The TBSV was also identified in the isolate of necrotic mosaic.Additional index words: Lilac ringspot, chlorotic ringspot, yellow ring, “spring” mosaic, necrotic mosaic, cherry leaf roll virus,Pseudomonas syringae van Hall.     

An inhibitor in faba bean sap suppressing infection of Chenopodium quinoa by bean yellow mosaic virus

An inhibitor in faba bean sap decreased the infectivity of bean yellow mosaic virus in undiluted sap to 0.2% of its potential infectivity calculated from diluted preparations.     

Occurrence of fungally transmitted wheat mosaic viruses in China

A soil-borne mosaic disease of winter wheat in Sichuan, Shaanxi, Hubei and Henan provinces was associated with infection by a virus with filamentous particles and that in Shandong, Anhui, Jiangsu and Zhejiang provinces by co-infection with this virus and soil-borne wheat mosaic virus. The virus with filamentous particles was identified serologically, by particle sizes, cytopathology and the molecular weights of the coat protein and the two RNA species to be either wheat spindle streak mosaic virus (WSSMV) or wheat yellow mosaic virus. These viruses are probably isolates of the same virus and the name WSSMV is preferred. In baiting tests using infested soil, the dilution endpoints for detecting WSSMV were 1/625-1/15625, and for the fungus vector, Polymyxa graminis, 1/3125-1/15625.     

Glycine mosaic virus: a comovirus from Australian native Glycine species

Two strains of a virus designated Glycine mosaic virus (GMV) were found in Glycine clandestina and G. tabacina, legumes indigenous to Australia and the western Pacific region. When transmitted by sap inoculation, GMV infected mostly leguminous species, and caused mosaic and mottling symptoms. The virus was not found naturally in soybean G. max, but it infected all of the 21 cultivars tested. GMV has isometric particles of c. 28 nm diameter, and produces three components with sedimentation coefficients of 60 S (top), 103 S (middle), and 130 S (bottom). Both middle and bottom components are required for infectivity. The virions contain two major proteins with molecular weights of c. 21 500 and 42 000. GMV produces large aggregates of particles in the cytoplasm of the mesophyll cells of pea Pisum sativum, and also induces amorphous membrane-bound bodies and cytoplasmic vesicles. The type strain (from New South Wales) reacts with antisera to Echtes Ackerbohnenmosaik, broad bean stain, and a Californian isolate of squash mosaic virus. The GW strain (from Queensland) reacts with all of the latter antisera, as well as with antisera to cowpea mosaic virus (Sb and Ark strains), bean pod mottle, and red clover mottle viruses, and is serologically related to, but not identical with, the type strain. These properties clearly establish GMV as a new member of the comovirus group.     

Identification, purification and some properties of a mosaic virus of okra (Hibiscus esculentus)

In the Ivory Coast, an apparently undescribed virus was isolated from okra (Hibiscus esculentus) in which it caused mosaic and leaf vein banding. The virus was sap transmissible to a wide range of plants and had a thermal inactivation point of 80 °C. It was named okra mosaic virus (OMV). A purification procedure was developed. Electron microscopy and analytical and density gradient centrifugation showed that OMV was an isometric virus accompanied by empty shells (top component). Serological tests showed OMV to be a member of the tymovirus group.