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This study reports the molecular characterization of a flexuous rod-shaped mycovirus, Botrytis virus X (BVX), infecting the plant-pathogenic fungus, Botrytis cinerea. BVX contains a ssRNA genome of 6966 nucleotides, and a poly(A) tract at or very near the 3' terminus. Computer analysis of the genomic cDNA sequence of BVX revealed five potential open reading frames (ORFs). ORF1 showed significant amino acid sequence identity to the replicase proteins of plant 'potex-like' viruses, including 73% identity to the RNA-dependent RNA polymerase (RdRp) region of the allexivirus, garlic virus A (GarV-A). The C-terminal region of ORF3 shared amino acid homology with plant 'potex-like' coat proteins. The remaining ORFs did not reveal significant homology with known protein sequences. BVX differs substantially from Botrytis virus F (BVF), another flexuous rod-shaped mycovirus characterized from the same B. Cinerea isolate. It is proposed that the mycovirus BVX belongs to a new, as yet unassigned genus in the plant 'potex-like' virus group, distinct from BVF.

Ryegrass mosaic virus (RGMV) is considered the most serious and widespread virus infecting temperate pasture grasses. The use of visible symptoms to diagnose infection is unreliable and ELISA analysis requires antibodies with broad cross-reactivity. Here we describe the production of a polyclonal antiserum (PAb-cp3'Delta) using a bacterially expressed RGMV coat protein fragment. The PAb-cp3'Delta antiserum is specific for RGMV and recognises RGMV strains from each major phylogenetic cluster. PAb-cp3'Delta may be used in ELISAs for fast, accurate and inexpensive detection of RGMV.

Sequences from the coat protein cistron of five ryegrass mosaic virus (RgMV) isolates indicated the presence of two distinct strains in New Zealand. The nucleotide differences between the strains, and their distribution, suggested that both strains were introduced recently, either as a mixed infection or as two independent introductions. The relationship between these New Zealand strains and other strains and isolates of RgMV, and their potential severity is discussed.

The sequence of the 3'-terminal 1492 nucleotides of the genome of a New Zealand isolate of clover yellow vein potyvirus (CYVV) has been determined. This sequence encodes a large open reading frame of 1314 nucleotides, the start of which was not identified, but which encodes a putative 272 amino acid coat protein. Downstream of the coat protein coding region is a 177 nucleotide untranslated sequence terminated by a polyadenylate tract. Comparison of the deduced CYVV-NZ coat protein amino acid sequence with two other strains of CYVV showed 86-93% similarity, suggesting CYVV-NZ should be regarded as a separate CYVV strain. CYVV-NZ shares with other CYVV strains a direct repeat of 14-16 nucleotides that is capable of forming a stem-loop structure. Examination of 35 strains of 15 other potyviruses showed a similar stem-loop structure conserved in all cases. A possible role in replication is hypothesized for the structure.