D.-E. Lesemann

The trapping of tymovirus particles on electron microscope grids by adsorption and serological binding.

Summary Many purified tymovirus particles are trapped on buffer-treated grids due to non-specific adsorption. Pre-treatment of grids with serum or addition of crude plant sap to virus preparations greatly inhibited non-specific adsorption. Specific serological binding on grids coated with homologous antiserum produced particle counts comparable to those achieved by non-specific adsorption on buffer-treated grids in the absence of plant sap. Specific serological binding was not influenced by crude sap of Nicotiana clevelandii. For both adsorption and serological binding there was a linear relationship between the log virus concentration and log particle counts at virus concentrations below approx. 10 µg/ml; at higher concentrations the grids were saturated. In the presence of excess virus, antisera at dilutions of less than 10-3 yielded lower particle counts than more dilute antisera. Heterologous reactions were detected only with viruses for which very close serological relationships had been found in the agar gel double-diffusion test. Heterologously bound virus was apparently not replaced by subsequently applied homologous virus. However, adsorbed bottom component virus particles could be replaced by top component particles of the same virus and vice versa.

New isolates of carnation Italian ringspot virus differ from the original one by having replication-associated proteins with a typical tombusvirus-like N-terminus and by inducing peroxisome- rather than mitochondrion-derived multivesicular bodies

Five new isolates of carnation Italian ringspot virus (CIRV) from cherry trees, Gypsophila and surface water differ from the original carnation isolate (CIRV-car) and also from Pelargonium necrotic spot virus (PelNSV) by having an ORF 1/ORF1-RT with a typical tombusvirus-like 5′end and by inducing the formation of peroxisome- rather than mitochondrion-derived multivesicular bodies (MVBs). This supports with natural isolates earlier conclusions reached by others with artificially produced hybrid viruses that the 5′end of ORF 1 determines from which organelle the MBVs will be derived. CIRV-car might have resulted from a natural recombination event with genome elements of a PelNSV-like virus.

Mechanical transmission of a strain of tulip breaking virus fromlilium longiflorum to chenopodium spp

A virus, mechanically transmitted fromLilium longiflorum toChenopodium spp., was identified in morphological, serological and ultrastructural studies as tulip breaking virus (TBV). Data presented indicate that the isolate differs from other TBV strains in host range and ultrastructural pathology.

Tobacco rattle virus genome alterations in the Hosta hybrid ‘Green Fountain’ and other plants: reassortments, recombinations and deletions

Tobacco rattle virus from a Hosta hybrid contained one RNA1 (Ho-1) and two RNA2 species (Ho-2a, Ho-2b). Whereas Ho-1 resembles TRV Al RNA1 from Alstroemerias, Ho-2a and Ho-2b resemble TRV TpO1 RNA2 from a potato field. Ho-2a has a complete RNA2-specific sequence, whereas that of Ho2-b carries a large deletion. The short RNA1-related 3’ end of Ho-2a is distinct from that of Ho-1, whereas the longer one of Ho-2b is identical to that of Ho-1. TRV RNA2 molecules may apparently become associated with different TRV RNA1 molecules, from which they can acquire 3’ends of various lengths while often losing large portions of their RNA2-specific sequences.