A New Strain of Cucumber Mosaic Virus Causing Mosaic Disease of Muskmelon

The virus causing mosaic of muskmelon in the Punjab is transmitted through seed, sap and aphids but not through beetle, whitefly, fungi or contact. It systemically infected Nicotiana tabacum (var. “White Burley” and CTRI-Special), N. glutinosa, N. rustica and Capsicum annuum besides various cucurbit hosts when inoculated mechanically. The virus gave positive reaction with the antiserum of cucumber mosaic virus and the particles are spherical in shape. The virus has been identified as a distinct strain of cucumber mosaic virus and is designated as muskmelon strain of cucumber mosaic virus (CMV-mst.).     

Nucleotide sequence of Chinese rape mosaic virus (oilseed rape mosaic virus), a crucifer tobamovirus infectious on Arabidopsis thaliana

The complete nucleotide sequence of Chinese rape mosaic virus has been determined. The virus is a member of the tobamovirus genus of plant virus and is able to infect Arabidopsis thaliana (L.) Heynh systemically. The analysis of the sequence shows a gene array that seems to be characteristic of crucifer tobamoviruses and which is slightly different from the one most frequently found in tobamoviruses. Based on gene organization and on comparisons of sequence homologies between members of the tobamoviruses, a clustering of crucifer tobamoviruses is proposed that groups the presently known crucifer tobamovirus into two viruses with two strains each. A name change of Chinese rape mosaic virus to oilseed rape mosaic virus is proposed.Abbreviations 2-ME 2-mercaptoethanol - EDTA ethylenediaminetetraacetic acid - SDS sodium dodecyl sulfate - UTR untranslated region - MP movement protein - CP capsid protein - CRMV Chinese rape mosaic virus - TVCV turnip vein clearing virus - PaMMV paprika mild mottle virus - PMMV-I pepper mild mottle virus (Italian isolate) - PMMV-S pepper mild mottle virus (Spanish isolate) - ToMV tomato mosaic virus - TMV tobacco mosaic virus - TMGMV tobacco mild green mosaic virus - ORSV odontoglossum ringspot virus - SHMV sunn hemp mosaic virus - CGMMV cucumber green mottle mosaic virus - ORMV oilseed rape mosaic virus     

Natural distribution, spread, and variation, in the tobacco mosaic virus infecting Nicotiana glauca in Australia

Nicotiana glauca is a naturalised introduced species widely distributed in Australia. A survey of stands in the central zone of its recorded distribution has shown that a type of tobacco mosaic virus which characteristically induces a bright yellow mosaic symptom (TMV-Y) is commonly associated with N. glauca throughout this zone. Surveys of a natural community of N. glauca less than 5 yr old, and in an experimental block, showed that TMV-Y could spread at a rate, and in a pattern, which could not be explained by contact transmission alone, and which indicated that an airborne vector was probably involved in transmission. These results together have led to the conclusion that the common association of TMV-Y with N. glauca is due to spread of the virus by an unknown vector(s). Seed transmission of TMV-Y in N. glauca has not been detected. Molecular hybridisation analysis has shown that all but one of the TMV-Y isolates studied were related to TMV-U², and that the isolate which was unrelated to U², was partially related to TMV-U¹, TMV-U⁵, and tomato mosaic virus. Selected isolates which showed a close relationship to TMV-U², also showed a close relationship to TMV-U⁵, a distant relationship to TMV-U¹, and tomato mosaic, and very little or no relationship with three other tobamoviruses (sunn-hemp mosaic virus, odontoglossum ringspot virus, and cucumber virus 4). These results show that the Australian TMV-Y isolates are similar to the TMV isolated from N. glauca in California.     

Occurrence of three distinct begomoviruses in cassava in Madagascar

The presence of East African cassava mosaic virus in association with cassava mosaic disease in Madagascar has previously been reported. We now describe virus isolates from mosaic‐affected Madagascan cassava with epitope profiles typical of African cassava mosaic virus, and an isolate with a nucleotide sequence similar to that of South African cassava mosaic virus. Thus, three distinct begomoviruses occur in cassava in Madagascar.     

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.     

An Isolate of Cucumber Mosaic Virus from Fluted Pumpkin in Nigeria

The properties of a virus isolated from fluted pumpkin (Telfairia occidentalis) was investigated. It produced symptoms in some members of the Solanaceae and Leguminosae, and was transmitted nonpersistently by the aphid, Aphis spiraecola. On the basis of these alone, it is distinct from another previously described virus, Telfairia mosaic virus, which neither caused symptoms in members of these families nor was it transmitted by insects. Furthermore, the virus in crude sap or purified preparations reacted with antiserum to cucumber mosaic virus (CMV), but not with antisera to several common viruses in Nigeria. Electron microscopic examination revealed isometric particles of 29 × 1 nm in diameter. These properties confirmed that the virus is an isolate of CMV, and closely resembles the Y-strain in causing systemic mosaic symptoms in Vigna unguiculata. From infectivity and pathogenicity tests, it is concluded that it is the main cause of mosaic disease in fluted pumpkin.     

The isolation and identification of rhubarb viruses occurring in Britain

Virus-like symptoms were common in British crops of rhubarb. All plants tested of the three main varieties, ‘Timperley Early’, ‘Prince Albert’ and ‘Victoria’, were virus-infected. Turnip mosaic virus and a severe isolate of arabis mosaic virus (AMV) were obtained from ‘Timperley Early’; and ‘Prince Albert’ contained turnip mosaic virus, cherry leaf roll virus (CLRV), a mild isolate of AMV and, infrequently, cucumber mosaic virus (CMV). The main commercial variety ‘Victoria’ contained turnip mosaic virus, CLRV, a mild isolate of AMV and, infrequently, strawberry latent ringspot virus (SLRV). All the viruses were identified serologically. The rhubarb isolates did not differ markedly from other isolates of these viruses in herbaceous host reactions, properties in vitro or particle size and shape. A rhubarb isolate of CLRV was distinguished serologically from a cherry isolate of the virus. Turnip mosaic virus, CLRV and SLRV, were transmitted with difficulty, but AMV isolates were readily transmitted by mechanical inoculation. Turnip mosaic virus was also transmitted to rhubarb by Myzus persicae and Aphis fabae. CLRV was transmitted in 6–8% of the seed of infected ‘Prince Albert’ and ‘Victoria’ rhubarb and in 72% of the seed of infected Chenopodium amaranticolor. Mild isolates of AMV were also transmitted in 10–24% of the seed of infected ‘Prince Albert’ and ‘Victoria’ plants.     

One‐step Multiplex RT‐PCR for Simultaneous Detection of Four Viruses in Tobacco

A one‐step multiplex RT‐PCR method has been developed for the simultaneous detection of four viruses frequently occurring in tobacco (Cucumber mosaic virus, Tobacco mosaic virus, Tobacco etch virus and Potato virus Y). Four sets of specific primers were designed to work with the same reaction reagents and cycling conditions, resulting in four distinguishable amplicons representative of the four viruses independently. This one‐step multiplex RT‐PCR is consistently specific using different combinations of virus RNA as templates, and no non‐specific band was observed. It has high sensitivity compared to single RT‐PCR. Moreover, field samples in China can be tested by this method for virus detection. Our results show that one‐step multiplex RT‐PCR is a high‐throughput, specific, sensitive method for tobacco virus detection.     

Purification and Identification of a South African Isolate of Watermelon Mosaic Virus – Morocco

Cucurbit crops in South Africa are seriously affected by a flexuous rod-shaped virus 706 to 770 nm long which causes the plant to be stunted, the leaves to display symptoms of chlorotic mosaic, dark green blisters and malformation, and fruit to be malformed. The virus was purified from infected Cucurbita pepo by extraction in 0.5 M borate buffer, pH 8, containing ethylenediaminotetra-acetic acid and mercapto-ethanol, clarification with chloroform, addition of Triton X-100, sedimentation by ultracentrifugation for which a sucrose cushion was used and centrifugation in 10 to 40 % sucrose gradients. The virus was mechanically transmitted to a limited host range with Chenopodium album, C. amaranticolor, C. quinoa and Gomphrena globosa being the only hosts infected outside the Cucurbitaceae. Luffa cylindrica, Cucumis metuliferus, Coccinia sessilifolia and Citrullus ecirrhosus all members of the Cucurbitaceae, were not infected by the virus. The virus was non-persistently transmitted by Myzus persicae, produced pinwheel and bundle inclusions in the plant cell cytoplasm and has a single coat protein with a molecular weight of 36,000 daltons and a degraded lighter component of 26,000 daltons. Serological comparisons with antiserum to watermelon mosaic virus 2, Papaya ringspot virus strain W and watermelon mosaic virus Morocco (WMV-Mor.) identified the virus as an isolate of WMV-Mor. It was found that WMV-Mor. is the dominant virus in all the main cucurbit producing areas of South Africa which were surveyed.     

Groundnut eyespot virus, a new member of the potyvirus group

A virus causing ‘eyespot’ leaf symptoms in groundnut plants was transmitted by sap-inoculation and by Aphis craccivora in the non-persistent manner. It infected 16 of 72 species from five of 12 families and was easily propagated in Arachis hypogaea and Physalis floridana. The virus has particles c. 13 × 755 nm and is serologically closely related to soybean mosaic and pepper veinal mottle viruses, and more distantly to four other potyviruses. The virus differs in host range, in vitro properties and serological properties from previously described strains of soybean mosaic and pepper veinal mottle viruses. It seems to be a distinct member of the potyvirus group and we propose the name groundnut eyespot virus.     

Further evidence for the recognition of Ullucus Mild Mottle Virus as a Distinct Tobamovirus

The affinities of Ullucus mild mottle virus (UMMV). purified by a modified procedure. were examined by immunoblotting and probing with antisera to five distinct tobamoviruses. RNA. isolated from purified virus, was used for in vitro protein translation in a wheat germ system and the products examined by denaturing polyacrylamide gel electrophoresis. The results of these investigations, together with a study of the double-stranded RNAs associated with infection. confirm that UMMV is a distinct, tobamovirus which has close affinities with tobacco mosaic, tomato mosaic and cucumber green mottle tobamoviruses and more distant relationships with ribgrass mosaic and odontoglossum ringspot tobamoviruses.     

Translationally controlled tumour protein: A protein necessary for potyvirus intracellular multiplication that supports plant infection by unrelated viruses

The multifunctional protein translationally controlled tumour protein (TCTP) was previously identified as necessary for infection by the potyvirus pepper yellow mosaic virus. Using turnip mosaic virus (TuMV) as a model to study potyvirus biology, we confirmed that TCTP has a positive effect on virus infection. Living cell confocal microscopy demonstrated that TCTP colocalises with 6K2-tagged replication vesicles and with a perinuclear globular structure typically observed during potyvirus infection. Also, TCTP silenced protoplasts showed reduced virus accumulation, quantified by qRT-PCR, which suggests an effect on virus replication, translation or other intracellular process. Finally, TCTP silencing in plants reduced the accumulation of two species belonging to Orthotospovirus and a Begomovirus genus, which are not closely related to potyviruses. The results suggest that TCTP is a general susceptibility factor to several unrelated viruses.     

Inheritance of resistance to potato y viruses in Phaseolus vulgaris L

Summary Resistance to watermelon mosaic virus-2 in Phaseolus vulgaris L. is conferred by two distinct dominant alleles at independent loci. Based on segregation data one locus is designated Wmv, the other, Hsw. The dominant allele Wmv from cv. Great Northern 1140 prevents systemic spread of the virus but viral replication occurs in inoculated tissue. In contrast, Hsw confers both local and systemic resistance to WMV-2 below 30C. At higher temperatures, plants that carry this allele in the absence of modifying or epistatic factors develop systemic veinal necrosis upon inoculation with the virus that results in rapid death. Patho-type specificity has not been demonstrated for either allele; both factors confer resistance to every isolate tested. A temperature-sensitive shift in epistasis is apparent between dominant alleles at these loci. Because Hsw is very tightly linked if not identical to the following genes for hypersensitivity to potyviruses I, (bean common mosaic virus), Bcm, (blackeye cowpea mosaic virus), Cam, (cowpea aphid-borne mosaic virus) and Hss (soybean mosaic virus), parental, reciprocal dihybrid F₁ populations, and selected F₃ families were inoculated with each of these viruses and held at 35 C. F₁ populations developed vascular necrosis completely or primarily limited to inoculated tissue, while F₃ families from WMV-2-susceptible segregates were uniformly susceptible to these viruses. The relationship between Hsw, Wmv and other genes for potyvirus resistance suggest patterns in the evolution of resistance and viral pathogenicity. Characterization of the resistance spectrum associated with each factor provides an additional criterion to distinguish genes for plant virus resistance.     

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.     

Transient protein expression in three Pisum sativum (green pea) varieties

The expression of proteins in plants both transiently and via permanently transformed lines has been demonstrated by a number of groups. Transient plant expression systems, due to high expression levels and speed of production, show greater promise for the manufacturing of biopharmaceuticals when compared to permanent transformants. Expression vectors based on a tobacco mosaic virus (TMV) are the most commonly utilized and the primary plant used, Nicotiana benthamiana, has demonstrated the ability to express a wide range of proteins at levels amenable to purification. N. benthamiana has two limitations for its use; one is its relatively slow growth, and the other is its low biomass. To address these limitations we screened a number of legumes for transient protein expression. Using the alfalfa mosaic virus (AMV) and the cucumber mosaic virus (CMV) vectors, delivered via Agrobacterium, we were able to identify three Pisum sativum varieties that demonstrated protein expression transiently. Expression levels of 420 ( 26.24 mg GFP/kgFW in the green pea variety speckled pea were achieved. We were also able to express three therapeutic proteins indicating promise for this system in the production of biopharmaceuticals.     

Evolutionary relationship of alfalfa mosaic virus with cucumber mosaic virus and brome mosaic virus

The amino acid sequences of the non-structural protein (molecular weight 35,000; 3a protein) from three plant viruses — cucumber mosaic, brome mosaic and alfalfa mosaic have been systematically compared using the partial genomic sequences for these three viruses already available. The 3a protein of cucumber mosaic virus has an amino acid sequence homology of 33.7% with the corresponding protein of brome mosaic virus. A similar protein from alfalfa mosaic virus has a homology of 18.2% and 14.2% with the protein from brome mosaic virus and cucumber mosaic virus, respectively. These results suggest that the three plant viruses are evolutionarily related, although, the evolutionary distance between alfalfa mosaic virus and cucumber mosaic virus or brome mosaic virus is much larger than the corresponding distance between the latter two viruses.     

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.     

Inheritance of resistance to potyviruses in Phaseolus vulgaris L. IV. Inheritance, linkage relations, and environmental effects on systemic resistance to four potyviruses

We have examined the genetics of systemic resistance in Phaseolus vulgaris to azuki bean mosaic virus (AzMV) and cowpea aphid-borne mosaic virus (CABMV) and the relationship of this resistance to a phenotypically similar resistance to watermelon mosaic virus (WMV) and soybean mosaic virus (SMV). In P. vulgaris cv Great Northern 1140 (GN1140), resistance to SMV and WMV has been attributed to the genes Smv and Wmv, respectively, which have been shown to segregate as a unit. Systemic resistance to AzMV is conferred by two incompletely dominant alleles, Azm1 and Azm2, at unlinked loci. At least three resistance alleles must be present at these two loci for systemic resistance to be expressed in the plant. Systemic resistance to CABMV in GN 1140 is conditioned by a dominant allele that has been designated Cam2. Under some environmental conditions, a recessive allele at an unlinked locus, cam3, also controls a resistant response to CABMV. Resistance to AzMV and CABMV does not assort independently from Wmv/Smv, but also does not consistently cosegregate, suggesting that perhaps in each case one of the factors involved in resistance is associated with Smv/Wmv.     

Plant proteases as interfering factors in the electron microscopic detection of alfalfa mosaic and bean yellow mosaic viruses inSolanum laciniatum Ait

Plant proteases rapidly destroy virus architecture in sap ofSolanum laciniatum Ait., with yellow mosaic symptoms but even under these conditions the partially digested amorphous nucleoproteins retain their immunospecificity and infectivity for a limited time. Homogenization with phenylmethylsulfonylfluoride inhibits efficiently host serine proteases and fully stabilizes the virus particles in plant sap and in partial purificates. During the electronmicroscopic examination of stabilized infectious saps in 12 out of 14 isolates of yellow mosaic ofS. laciniatum besides alfalfa mosaic virus a poty-virus was disclosed. This was identified serologically and by transmission tests as a weakly virulent type of bean yellow mosaic virus.