The complete sequence of a UK strain of black raspberry necrosis virus.

The complete nucleotide sequence of a UK strain of the sadwavirus Black raspberry necrosis virus (BRNV) was obtained by amplification and sequencing of virus RNA from infected plants grown in a raspberry plantation in Aylth, Scotland. The RNA1 was 7,572 nucleotides (nt) in size and RNA2 was 6,350 nt in size, each excluding the 3' poly-A tail. The RNA1- and RNA2-encoded polyproteins are predicted to be processed into (RNA1) a protease cofactor, an RNA helicase, the VpG, a 3C-like protease, an RNA-dependent RNA polymerase and an AlkB protein, and (RNA2) a movement protein and two capsid proteins.

Rubus chlorotic mottle virus, a new sobemovirus infecting raspberry and bramble.

The complete nucleotide sequence of a new member of the unassigned genus Sobemovirus, isolated from raspberry and bramble plants in north east Scotland and given the name Rubus chlorotic mottle virus (RuCMV), was obtained. The virus has a single, positive-strand RNA genome of 3,983 nucleotides and, in common with other sobemoviruses, contains four open reading frames (ORFs) encoding, from 5' to 3', the P1 protein that is likely to be a suppressor of RNA silencing, ORF2a that has homology to serine-proteases, ORF2b that is the probable RNA dependent RNA polymerase, and ORF3 that is the coat protein. ORF2b protein is potentially expressed as a fusion with ORF2a protein by a -1 frameshift at the heptanucleotide sequence UUUAAAC. Phylogenetic analyses showed that RuCMV is a distinct virus not closely related to any of the other sequenced sobemoviruses. Based on the obtained sequence a full-length cDNA copy of RuCMV was cloned and in vitro transcripts derived from this clone were shown to be fully infectious.

A New Badnavirus in Ribes Species, its Detection by PCR, and its Close Association with Gooseberry Vein Banding Disease.

Gooseberry vein banding disease (GVBD) affects Ribes species and cultivars worldwide. It is the second most important virus-like disease in these crops after black currant reversion disease. In this paper, we describe a bacilliform virus, Gooseberry vein banding associated virus (GVBAV), which is associated closely with GVBD, and provide evidence that GVBAV is a distinct species within the genus Badnavirus. Purified GVBAV particles were ca. 120 × 30 nm in size and contained dsDNA. The sequence of a 1.5-kb DNA fragment amplified from viral genomic DNA was similar to those of a wide range of badnaviruses and contained motifs characteristic of the RNase H domain of the badnavirus open reading frame (ORF) III polyprotein. Phylogenetic analyses suggest that GVBAV is most closely related to Spiraea yellow leaf spot virus. Using sequence derived from the polymerase chain reaction (PCR)-amplified DNA fragment, virus-specific primers were designed. These primers were used in PCR to assay for GVBAV in a range of Ribes germplasm affected with GVBD, with other unrelated virus-like diseases and viruses found in Ribes, and in healthy plants. GVBAV was detected in all of 58 GVBD-affected plants from diverse sources, but not from healthy Ribes plants nor from plants infected with other viruses.

Purification and properties of a new virus from black currant, its affinities with nepoviruses, and its close association with black currant reversion disease.

ABSTRACT Black currant reversion is a virus-like disease whose causal agent has not been identified. In rooted cuttings of a black currant plant affected with the severe form of the disease, pronounced chlorotic line patterns and ringspots developed in newly emerging leaves. From such symptom-bearing leaves, a virus was mechanically transmitted with difficulty to Chenopodium quinoa and, from this host, to other herbaceous test plants. The virus was purified and partially characterized, and the purified viri-ons were used for antiserum production. Virus particles were isometric, approximately 27 nm in diameter, and sedimented as two nucleoprotein components. They contained a protein species with a molecular mass of 55 kDa, which was readily degraded into a 54-kDa protein and two major RNA components of about 6,700 and 7,700 nucleotides (nt), each with a poly(A) tail. Most of these properties are shared by nepoviruses, but the virus was serologically unrelated to 14 nepoviruses or putative nepovi-ruses tested. However, the deduced sequence of 1,260 nt at the 3' end of one of the viral RNA species was distinct from any known viral sequence, except that it contained short regions of homology to the 3' terminal sequences of RNAs of seven other nepoviruses and two comovi-ruses. To detect this virus in Ribes plants, primers were designed from the known sequence to amplify a 210-nt region of the cDNA of the virus RNA using an immunocapture reverse transcriptase polymerase chain reaction (IC-RT-PCR) protocol. Using this assay for the virus, we associated its presence with two recognized forms of black currant reversion disease occurring in Finland, Scotland, or New Zealand. We also detected the virus in vector gall mites from reverted plants and in black currant plants on which such vector mites had fed. However, the virus was not detected by IC-RT-PCR in known healthy Ribes plants; in Ribes plants free from reversion, but affected by three other distinct virus-like diseases of Ribes; or in plants infected with arabis mosaic, strawberry latent ringspot, or raspberry ringspot nepoviruses. These data suggest that this virus may be the causal agent of reversion disease, and it is tentatively called black currant reversion associated virus.

Species identification of Cecidophyopsis mites (Acari: Eriophyidae) from different Ribes species and countries using molecular genetics.

Cecidophyopsis mites were studied by PCR amplification of parts of their ribosomal DNA, followed by restriction enzyme analysis. Mite specimens on Ribes nigrum (black currant) from six countries gave the same digestion pattern, which was distinct from the pattern for mites found on R. rubrum from Poland and Finland and for R. grossularia from the USA. This suggests that each Ribes species is host to a different mite species: C. ribis, C. selachodon and C. grossulariae, respectively. Two other mite samples from R. alpinum and R. aureum were identical but were distinct from each of the other species.