Differentiation and distribution of cordyline viruses 1-4 in Hawaiian ti plants (Cordyline fruticosa L.)

Molecular characterization of Cordyline virus 1 isolates infecting yam (Dioscorea spp)

Cordyline virus 1 (CoV1) is a velarivirus that has so far only been reported in ornamental Ti plants (Cordyline fruticosa). Using high-throughput sequencing, we identified CoV1 infection in yam accessions from Vanuatu. Using a specific RT-PCR assay, we found that CoV1 is also present and highly prevalent in Dioscorea alata, D. cayenensis, and D. trifida in Guadeloupe. Phylogenetic analysis showed that CoV1 isolates infecting yam in Guadeloupe display a low level of molecular diversity. These data provide insights into the transmission of CoV1 in yam in Guadeloupe.

Novel viruses associated with plants of the family Amaryllidaceae in South Africa

Nineteen samples from members of the plant genera Agapanthus, Clivia, Hippeastrum, and Scadoxus were collected from gardens in the Gauteng and Western Cape provinces of South Africa. The plants displayed highly variable symptoms of viral disease, including chlorosis, necrosis, streaking, and ringspot. RNAtag-seq was used to characterize the associated viral populations. Plants of the genus Agapanthus were found to be associated with three novel viruses from the families Caulimoviridae, Closteroviridae, and Betaflexiviridae; plants of the genus Clivia were associated with novel members of the families Potyviridae and Betaflexiviridae; and plants of the genus Scadoxus were associated with a novel member of the family Tospoviridae. Nerine latent virus was associated with plants of the genera Agapanthus, Clivia, and Hippeastrum, while hippeastrum mosaic virus was associated exclusively with a Hippeastrum cultivar.

Characterization of Ti Ringspot-Associated Virus, a Novel Emaravirus Associated with an Emerging Ringspot Disease of Cordyline fruticosa

Ti ringspot is an emerging foliar disease of the ti plant (Cordyline fruticosa) in Hawaii that is quickly spreading throughout the islands. Symptoms include small chlorotic ringspots on leaves that often coalesce to form larger lesions. Although several virus species have been discovered in symptomatic plants, none have been associated with these symptoms. Here, we report and characterize a novel virus closely associated with ti ringspot symptoms in Hawaii. The presence of double membrane bodies approximately 85 nm in diameter in symptomatic cells and sequence analyses of five genomic RNA segments obtained by high-throughput sequencing indicate that this virus is most closely related to members of the plant virus genus Emaravirus. Phylogenetic and sequence homology analyses place this virus on a distinct clade within the Emaravirus genus along with High Plains wheat mosaic emaravirus, blue palo verde broom virus, and Raspberry leaf blotch emaravirus. Sequence identity values with taxonomically relevant proteins indicate that this represents a new virus species, which we are tentatively naming ti ringspot-associated virus (TiRSaV). TiRSaV-specific reverse transcription PCR assays detected the virus in several experimental herbaceous host species following mechanical inoculation. TiRSaV was also detected in eriophyid mites collected from symptomatic ti plants, which may represent a putative arthropod vector of the virus.

Nucleotide sequence and genome organization of a new proposed crinivirus, tetterwort vein chlorosis virus

The genome of tetterwort vein chlorosis virus (TVCV) from South Korea has been completely sequenced. Its genomic organization resembles those of other criniviruses, with several new features, indicating that TVCV is a member of a new species in the genus Crinivirus, family Closteroviridae. RNA1 contains 8467 nucleotides, with at least four opening reading frames (ORFs). ORF1a encodes a protein with predicted papain-like protease, methyltransferase, and helicase activities. ORF1b encodes a putative RNA-dependent RNA polymerase that is apparently expressed through a +1 ribosomal frameshift. RNA2 contains 8113 nucleotides encoding at least nine proteins, similar to most crinivirus RNA2s. The 3' untranslated regions of the bipartite RNA genome share 82.1% nucleotide sequence identity.