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The structure and organization of the large (L) RNA of iris yellow spot virus (IYSV) was determined, and with this report, the complete genomic sequence of IYSV of the genus Tospovirus, family Bunyaviridae has been elucidated. The L RNA of IYSV was 8,880 nucleotides in length and contained a single open reading frame in the viral complementary (vc) strand. The primary translation product of 331.17 kDa shared many of the features of the viral RNA-dependent RNA polymerase (RdRp) coded by L RNAs of known tospoviruses. The 5′ and 3′ termini of IYSV L RNA (vc) contain two untranslated regions of 33 and 226 nucleotides, respectively, and both termini have conserved terminal nucleotides, another common feature of tospovirus genomic RNAs. Conserved motifs characteristic of RdRps of members of the family Bunyaviridae were present in the IYSV RdRp. [ABSTRACT FROM AUTHOR]

Two tymoviruses were identified in plants of Diascia × hybrida ‘Sun Chimes™ Coral’ that exhibited chlorotic mottling and reduced growth. A strain of Nemesia ring necrosis virus (NeRNV) designated NeRNV-WA was detected in symptomatic plants; the deduced amino acid sequence is virtually identical to that of the previously reported NeRNV-Nf from Nemesia fruticosa. Sequence analysis also revealed the presence of a new tymovirus, and the entire genomic sequence of this virus was determined. The genome of 6,290 nucleotides was organized into three potential open reading frames (ORFs) typical of viruses in the genus Tymovirus. Based on sequence identity to tymovirus sequences, ORFs I to III encoded the replicase, movement protein and coat protein, respectively. Amino acid sequence identities to those of NeRNV-Nf were 84.8, 50.3 and 94.8%, respectively. The 5′-untranslated region could potentially form four hairpin structures. Secondary structure analysis of the 3′-terminus showed that the RNA can form a transfer-RNA-like structure that has an anticodon specific for histidine. Only 77.9% nucleotide identity was found when complete genomic sequences of this tymovirus from diascia and NeRNV-Nf were compared. The name Diascia yellow mottle virus (DiaYMV) is proposed for this new tymovirus. [ABSTRACT FROM AUTHOR]

A new potexvirus affecting ornamental allium spp in the Netherlands was identified and characterized at the molecular level. The virus had a single-stranded RNA genome of 7100 bp (excluding the 18 bp poly A tail). The genome organization was found to be typical of members of the genus Potexvirus and consisted of five open reading frames (ORF). Nucleotide and amino acid sequence comparisons with those of known potexvirus members showed that this virus is related to Hosta virus X and Hydrangea ringspot virus. Sequence similarities and phylogenetic relationships suggested that the allium virus is a new and distinct species in the genus Potexvirus and the name, Allium virus X (AlVX) is proposed. [ABSTRACT FROM AUTHOR]

Plants of Triteleia hyacinthina, Triteleia ixioides Starlight, and Triteleia laxa Corina with severe mosaic and yellow vein-banding were found to be infected with a potyvirus. The 3′-terminal region of the virus was amplified by RT-PCR from total RNA using a potyvirus-specific degenerate primer (poty5P: 5′ GGN AAY AAY AGY GGN CAR CC 3′) and an oligo-dTprimer. The sequence generated included the 3′-NIb protein coding region (680 nucleotides), the entire coat protein coding region (840 nucleotides), and 3’-untranslated region (UTR) (253 nucleotides). Amino acid identity of the whole CP between the triteleia virus and potyvirus member ranged from 54% Apium virus Y (ApVY) to 67% Auraujia mosaic virus (ArjMV) and Twisted-stalk chlorotic streak virus (TSCSV) and the core ranged from 59% (ApVY) to 75% (ArjMV). The 3-UTR showed no significant homology with other known potyviruses. Phylogenetic relationships suggest this triteleia virus is a new member of the Potyvirus genus and the name of “Triteleia mosaic virus” (TriMV) is proposed. This is the first report of a potyvirus infecting triteleia. [ABSTRACT FROM AUTHOR]

Symptoms of 'black death' were observed on HelIeborus spp. in each of three independent nurscries from across the United States. A new virus of the genus Carlavirus was identified in association with this disease. Symptomatic plants contained curved, rod-shaped particles averaging 800 by 17 nm, and yielded predominant bands of double-stranded (ds)RNA corresponding to approximately 9.0, 2.6, and 1.7 kbp. Amplification with degenerate primers for carlaviruses yielded a product of approximately 3,000 bp from diseased plants. Complete genomic sequences of two virus isolates were determined. Particle size, dsRNA patterns, genome organization, and sequence were consistent with members of the family Flexiviridae, genus Carlavirus. The name Helleborus net necrosis virus (HeNNV) is proposed for the virus associated with black death of Helleborus spp. in the United States. The sequence of the 3′ terminus of Helleborus mosaic virus (HeMV) (genus Carlavirus) was also determined. Nucleotide sequences of HeNNV and HeMV were only 49% identical, revealing the distinct nature of these viruses. Assays for other viruses failed to reveal a consistent association of any other virus with black death symptoms. Cucumber mosaic virus was detected in hellebore specimens both with and without distinct black death symptoms. [ABSTRACT FROM AUTHOR]