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M B von Wechmar

Publications and source records attributed to M B von Wechmar.

15 recordsLinked to original sources
PubMed2001

The relative infectivities and genomic characterisation of three distinct mastreviruses from South Africa.

The genomic nucleotide sequences of the cloned agroinfectious genomes of three South African mastreviruses obtained from Zea mays, a Setaria sp., and Panicum maximum (designated MSV-Kom, MSV-Set, and PanSV-Kar respectively), were determined. Additionally, their relative infectivities and virulence were analysed in a range of differentially susceptible wheat, maize, and barley genotypes. MSV-Kom produced moderate to severe streak symptoms in all maize genotypes tested, but only moderate to very mild symptoms in the wheat and barley genotypes. MSV-Set infected only the susceptible to tolerant maize genotypes, but was generally more severe in the barley and wheat genotypes than MSV-Kom. PanSV-Kar was incapable of infecting any of the wheat and barley genotypes and only produced very mild symptoms on the three most sensitive maize genotypes. Genomic characteristics in common with related mastreviruses were identified. Phylogenetic analysis indicated that while MSV-Kom was closely related to previously sequenced MSV isolates, MSV-Set and PanSV-Kar represented distinctly novel strains of MSV and PanSV respectively. In the case of MSV-Set, this is the most distantly related MSV strain yet characterised.

Animals↗
PubMed1992

Fungal transmission of a potyvirus: uredospores of Puccinia sorghi transmit maize dwarf mosaic virus.

Maize dwarf mosaic virus (MDMV) and maize rust, Puccinia sorghi Schw., occur as natural infections on cultivated maize in South Africa. P. sorghi often occurs as a secondary late infection on maize plants which have already been infected with MDMV earlier in the season, either seed or aphid transmitted. When MDMV isolates from maize plants naturally infected by both virus and fungus were propagated by sap inoculation in plant growth rooms, residual uredospores in the sap gave rise to the development of uredia under conditions of high humidity. When uredospores developing on MDMV-B-infected plants were germinated on virus free maize seedlings, these plants became infected with MDMV-B. Similarly, when uredospores, originating from maize plants infected with MDMV-A, were scattered onto virus free maize seedlings, these plants became infected with MDMV-A. The presence of virus on uredospores in infected plant tissue was visualized by indirect immunofluorescence. Identification of virus infection was by DAS-ELISA and immunoelectro-blotting utilizing strain-specific antisera. Virus transmission occurred between closely situated plants which had no actual contact (unaided transmission). MDMV-B transmission by uredospores, to new maize seedlings, has been maintained for three successive years (1988-1991) in a plant growth room. The MDMV-B isolate remained sap and non-persistently aphid transmissible.

Animals↗
PubMed1992

Genome typing of southern African subgroup 1 geminiviruses.

The relatedness of subgroup 1 geminiviruses from a variety of naturally infected southern African graminaceous hosts was compared by DNA cross-hybridization, restriction endonuclease mapping and partial sequencing. Cross-hybridization divided the viruses into three groups: those closely related to maize streak virus (MSVs), and separate groups comprising a Panicum sp. virus (PanSV) and two sugarcane viruses (SSVs). Restriction mapping and comparisons, and phylogeny reconstructions from map data, showed that mapped and sequenced maize viruses were all highly similar; that two viruses of grasses and wheat bore limited resemblance to each other and to MSV, and that a mapped local and a sequenced Kenyan PanSV were similar, but that these and the two SSVs were dissimilar to each other and to all other subgroup 1 geminiviruses. The conclusions were: that maize viruses and the two viruses of wheat and grasses are probably strains of MSV; that two SSVs are only distantly related and distinct from MSVs; that the PanSVs are closely related to one another, but also distinct from other viruses; that all of the viruses in this study are part of a 'MSV-related sub-subgroup' of geminiviruses. Partial sequencing of cloned genomes reinforced conclusions drawn from other data, and indicated a definite relationship between the mapped and sequenced Panicum viruses. The implications of the results for taxonomic and epidemiological purposes are discussed.

Africa↗
PubMed1992

Two novel viruses associated with severe disease symptoms of the green stinkbug Nezara viridula.

Two viruses were isolated from green stinkbugs (Nezara viridula) with severe disease symptoms. These viruses have been named N. viridula virus type 1 (NVV-1) and NVV-2 according to their relative sedimentation coefficients. NVV-1 is a small picorna-like virus with a diameter of 29 nm, a buoyant density in CsCl of 1.34 g/ml and a sedimentation coefficient of 153S. NVV-1 particles contain a 9.4 kb ssRNA segment and have three coat proteins of M(r)s 32,100, 31,500 and 30,700. NVV-2 sediments as two components on sucrose gradients; the top 104S component consists almost entirely of 41 nm empty capsids and the faster sedimenting 177S component consists of intact 39 nm spherical particles. NVV-2 particles have a buoyant density in CsCl of 1.39 g/ml and consist of one major protein of M(r) 73,800 and at least two minor proteins of M(r)s 13,500 and 16,500. Only one dsRNA segment of 6.2 kb was identified. The properties of NVV-2 are similar to those of the Totiviridae. Individual stinkbugs were infected with either NVV-1 or NVV-2, or with a mixture of the two viruses. Re-infection of virus-free stinkbugs with the mixture resulted in typical disease symptoms. Both viruses were vertically transmitted through the eggs and insects were infected by surface contamination of their food source.

Animals↗
PubMed1991

Characterization of the sugarcane streak agent as a distinct geminivirus.

The relationship between maize streak virus and the geminivirus causing streak in sugarcane was investigated. The DNA of sugarcane streak virus does not cross-hybridize detectably with that of maize streak virus and vice versa. Restriction mapping of native replicative form viral DNA (genome size 2.7 kb) and of cloned viral DNA, combined with limited sequencing and estimated DNA sequence divergence, showed that sugarcane streak virus is as unrelated to maize streak virus and digitaria streak virus as these are different from each other. The virus is only distantly related to wheat dwarf virus and chloris striate mosaic virus. Based on these results, we propose that the agent causing sugarcane streak is a distinct geminivirus.

Blotting, Western↗
PubMed1989

Characterization of southern African isolates of maize streak virus: typing of three isolates by restriction mapping.

The genomic replicative form DNAs (RF-DNA) of three maize streak virus isolates (MSV-CT, MSV-PE, and MSV-SW) from widely separated locations in southern Africa were characterized by restriction endonuclease mapping in order to assess the feasibility of using the technique to determine genetic variability between isolates. The viruses were transmitted to and propagated in laboratory-grown maize by the leafhopper vector Cicadulina mbila (Naudé). MSV-PE produced more severe symptoms than MSV-CT and MSV-SW; the isolates were serologically identical in 'western' immunoblot tests, but distinct in 'sandwich' enzyme-linked immunosorbent assays. RF-DNA of all three isolates was prepared from infected maize; the RF-DNA of MSV-CT and MSV-PE was cloned in a plasmid vector in Escherichia coli. Restriction maps were generated from this cloned DNA and from the RF-DNA of MSV-SWA. The maps were similar in regions expected to be conserved, but there were also important differences between all isolates. The implications of these results, and of relationships amongst these and other sequenced isolates of MSV, are discussed.

Africa, Southern↗
PubMed1982

Enzyme-assisted immune detection of plant virus proteins electroblotted onto nitrocellulose paper.

A technique for the detection of plant virus coat proteins in plant sap is described. The method entails the electroblotting of sodium dodecyl sulphate-polyacrylamide gel electrophoresis-fractionated plant extracts onto nitrocellulose paper, probing the paper with virus-specific rabbit antisera, and indirect detection of virus proteins with horseradish peroxidase-conjugated goat anti-rabbit globulins. The sensitivity and specificity of the technique were tested using brome mosaic and barley stripe mosaic viruses. As little as 1 ng per track of virus protein was detectable, either as pure virus or when mixed with plant sap. Distant serological relationships were detected amongst tobamoviruses, and amongst the bromoviruses, with single antisera. The uses of the technique in probing capsid configuration in a presumed aphid picornavirus, and in routine diagnostic practice, are described.

Antigens, Viral↗
PubMed1980

Isolation of viral IgY antibodies from yolks of immunized hens.

Antibodies were isolated from the yolks of hens that were immunized with a variety of plant viruses by the use of polyethylene glycol (PEG). A concentration of 3.5% of the polymer caused the lipids and vitellin to separate, and the IgY was then precipitated with 12% PEG. The titre of the isolated antibody appears to remain at a high level after cessation of the course of immunization. Antibodies derived from the yolks of hens appear to have titres similar to those found in serum of rabbits immunized simultaneously. The observation made by several authors that a high salt concentration enhances fowl serum antibody precipitin titres could not be corroborated with 'yolk' antibodies directed against several plant viruses.

Animals↗
PubMed1980

Antibodies to proteins from yolk of immunized hens.

Immunoglobulins IgY, extracted from yolks of hens immunized against several proteins and natural mixtures of proteins were examined by the Ouchterloney gel diffusion and Laurell immuno-electrophoresis techniques. The molecular weights of the proteins ranged from 8 x 10(6) to less than 2 x 10(4). The hens produced IgY antibodies readily when injected with the high molecular antigens > 150 000 but did not react as well to antigens of relatively low molecular weight < 30 000. Optimal precipitin reactions were obtained with low molecular antigens when the agarose gel contained 1.5 M NaCl. Salt concentration (0.15-1.5 M NaCl) has no effect on the precipitin reaction in gels on the systems of high molecular antigens and their IgY antibodies apart from a displacement of the precipitin line. From the relative positions of the precipitin lines to the wells containing the reactants it would appear that the IgY formed dimers when the concentration of NaCl is 1.6 M and remain as monomers in gels containing 0.15 M NaCl. An explanation of the salt effect is offered.

Amoeba↗
PubMed1978

Electrophoresis in gels suspended in hydrophobic solvents.

Protein components in mixtures may be separated by zone electrophoresis in columns of gel suspended in hydrophobic solvents. The method is useful for the location of specific antibodies in IgG electrophoretic spectra.

Electrophoresis, Agar Gel↗
PubMed1978

Preparative immunoabsorption electrophoresis.

A method for separating a component from a mixture of antigens is described. The component which may be a virus or subfraction of a virus, is isolated by driving the mixture by electrophoresis through a gel containing precipitating antibodies directed against the unwanted components. The method is illustrated by the isolation of hepatitis B antigen from whole serum and by the separation of wild cucumber mosaic virus from a strain of tobacco mosaic virus.

Absorption↗