|Guaragna, Mary Ann|
|Van Buren, Tyler - RIVERHILL H.S.,COLUMBIA,M|
|Putnam, Melodie - OREGON STATE UNIV,CORVALL|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2007
Publication Date: April 16, 2008
Repository URL: http://hdl.handle.net/10113/18387
Citation: Jordan, R.L., Guaragna, M.A., Van Buren, T., and Putnam, M.L. 2008. First report of a new potyvirus, Tricyrtis virus Y, and Lily virus X Potexvirus, in Tricyrtis formosana in the United States. Plant Disease. 92:648. Interpretive Summary: Tricyrtis formosana is an herbaceous perennial in the Liliaceae family. It grows approximately 2 to 3 feet high in moist shady areas. Also known as Toad Lily, this plant has unique small spotted lily'like flowers that grow in clusters. Originally native to Asia, T. formosana is now used in the United States as an ornamental border plant in woodland and shade gardens. A T. formosana var. stolonifera plant from a commercial grower in Oregon showing chlorosis and mild mosaic symptoms tested positive for potyvirus in a serological assay using our genus Potyvirus broad spectrum reacting PTY-1 monoclonal as the detecting antibody. Electron microscopic examination of negatively stained leaf-dip preparations from symptomatic leaves however showed a mixture of two sizes of flexuous rod-shaped particles, some resembling potyviruses, and some resembling potexviruses. Total RNA preparations from infected leaves were used in RNA cloning assays using "generic" potyvirus-specific or potexvirus-specific primers, which amplify various highly conserved fragments from these two different virus genera. The cloned nucleotide and putative coat protein amino acid sequences from the infected Toad lily plant were compared to the corresponding regions of other potyvirus and potexvirus sequences available in the International databases. Pairwise comparisons of the Tricyrtis potyvirus sequence indicated high similarity with members of the Bean common mosaic virus (BCMV) group of potyviruses. Phylogenetic analysis results suggest that this virus is a new species in the genus Potyvirus, which we have tentatively named Tricyrtis virus Y (TrVY). Pairwise comparisons of the Tricyrtis potexvirus sequence showed 89-99% identity with Lily virus X (LVX) gene sequences. Dividing plants for propagation may transmit both of these viruses by vegetative propagation and mechanical contact. The potyvirus TrVY could also be aphid-transmitted, but there are no known invertebrate vectors for most all potexviruses. To our knowledge this is the first description of this potyvirus, the first report of any potyvirus in T. formosana and the first report of LVX in Tricyrtis formosana. This information will be useful to nurseries in their screening assays to detect and control these viruses in the parent propagation stock lines and subsequently in the large scale plant production phases.
Technical Abstract: Tricyrtis formosana (Toad lily) is an herbaceous perennial in the family Liliaceae. Originally native to Asia, T. formosana is now used in the United States as an ornamental border plant in woodland and shade gardens. A T. formosana var. stolonifera plant showing chlorosis and mild mosaic symptoms obtained from a commercial grower in Columbia County, Oregon tested positive for potyvirus in an antigen-coated plate ELISA using our genus Potyvirus broad spectrum reacting PTY-1 monoclonal as the detecting antibody. Electron microscopic examination of negatively stained leaf-dip preparations from symptomatic leaves showed a mixture of two sizes of flexuous rod-shaped particles, some approximately 700 nm long (resembling potyviruses), and some approximately 470 nm long (resembling potexviruses). Total RNA extracts from the symptomatic toad lily were used in reverse transcription-polymerase chain reaction (RT-PCR) assays with 'generic' potyvirus-specific or potexvirus-specific primers. The degenerate primers for the genus Potyvirus direct the amplification of highly conserved 700bp or 1600bp fragments from the 3' terminus of most potyviruses. Overlapping potexvirus cDNA clones were generated using degenerate genus Potexvirus replicase primers and, later, virus-specific primers in 3' RACE. The RT-PCR amplified fragments were cloned using standard 'TA cloning' procedures and sequenced using dye-terminator chemistry. BLAST analysis of the 1688nt potyvirus sequence (GenBank Accession No. AY864850) showed highest identity with members of the Bean common mosaic virus (BCMV) subgroup of potyviruses. Pairwise amino acid comparison of the CP region of the Tricyrtis potyvirus showed 78% identity to strains of Bean common mosaic necrosis virus, 77% identity with Soybean mosaic virus and Ceratobium mosaic virus, 72-76% identity to strains of BCMV, and only 50-64% identity with 54 other potyviruses. Additionally, similar pairwise analysis of the CP nucleotide sequence and 3'NCR of the Tricyrtis potyvirus generally revealed the same identity trend as described for the CP amino acid sequences, albeit with the highest nt identities at less than 73% for CP and less than 66% for the 3'NCR. These results suggest that this virus is a new species in the genus Potyvirus, which we have tentatively named Tricyrtis virus Y (TrVY). BLAST analysis of the 3' terminal 3010nt potexvirus sequence (GenBank Accession No. AY864849) showed 89% nucleotide identity with Lily virus X (LVX; GenBank Accession No. AJ633822). Pairwise amino acid comparisons of the putative gene products revealed 98, 95 and 99% identity with LVX TGBp1, TGBp2, and CP, respectively, and 97% identity with the 108nt 3'NCR. Additionally, a 94% amino acid identity with a TGBp3'like region lacking a normal AUG start codon, as has been reported for LVX, was also observed in this "LVX-TF" isolate. Homology with other members of the genus potexvirus was less than 50% for these corresponding genes and gene products. Dividing plants for propagation may transmit both of these viruses by vegetative propagation and mechanical contact. The potyvirus TrVY could also be aphid-transmitted, but there are no known invertebrate vectors for potexviruses, except for Potato aucuba mosaic virus. This is the first description of this potyvirus and the first report of any potyvirus in T. formosana. LVX has been reported in Lilium formosanum but to our knowledge this is also the first report of LVX in Tricyrtis formosana.