Identification and Molecular Characterization of a Potyvirus Isolated from Native Larkspur (Delpinium glaucum) in Alaska

Authors: ROBERTSON, NANCY; BROWN, KATHRYN

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2009
Publication Date: 4/1/2009
Citation: Robertson, N.L., Brown, K.L. 2009. Identification and Molecular Characterization of a Potyvirus Isolated from Native Larkspur (Delpinium glaucum) in Alaska. Plant Disease. 93(4):428.

Interpretive Summary: Wild larkspur, Delphinium glaucum, grows throughout most of Alaska along roadsides and in forests, and is often used as an ornamental plant. Severe leaf vein-clearing and chlorotic mosaic were first noticed on D. glaucum plants at the Georgeson Botanical Garden in Fairbanks, Alaska in 2000. Although the plants continued to produce showy flowers through 2008, they developed severe stunting. A new potyvirus was isolated from leaf tissue and confirmed by biological studies and molecular assays that included electron microscopy, protein analysis, serology, RT-PCR (reverse transcriptase –polymerase chain reaction) analysis, cloning, and sequencing. We conclude that the plants were infected with a new virus species in the genus Potyvirus, and propose to tentatively name it Delphinium vein-clearing virus (DeVCV). This is the first report of a virus isolated from D. glaucum, and represents an additional virus to those found in native plants. New viruses that are discovered from native plants are important in identifying potentially new pathogens that pose a threat to other ornamental and crop plants.

Technical Abstract: Delphinium glaucum (larckspur) plants at the Georgeson Botanical Garden in Fairbanks, Alaska displayed leaf vein-clearing and chlorotic mosaic in 2000, and by 2008, were severely stunted. Purified preparations and leaf dips examined by electron microscopy contained many flexuous filamentous particles. Virion protein extractions analyzed on SDS-PAGE produced prominent bands about 35kDa, presumed to be the coat protein. Potyvirus identity was confirmed using universal potyvirus antiserum in western blots and ELISA assays (Agdia, Inc.). A general protocol for RT-PCR potyvirus detection was used to generate genomic segments for sequence analysis. The expected fragments for the helper component protease, HP (~700 bp), cylindrical inclusion CI (~700 bp), and 3'-end (~1.7 kbp) were produced, cloned, sequenced. The sequenced 3'-end (1674 nt minus poly(A)tail) revealed a partial nuclear inclusion protein, NIb (1-630 nt), coat protein, CP (631-1443 nt), and 3'-untranslated region (1447-1674 nt) attached to a poly(A) tail. Searches in GenBank for percent identities of the nucleotide (BlastN) and amino acid (BlastP) comparisons resulted in highest similarities in conserved regions among members in the genus Potyvirus. However, none of the identities were sufficient for inclusion with an existing potyvirus species. We conclude that the isolated virus is a new virus species in the genus Potyvirus, and propose to tentatively name it Delphinium vein-clearing virus (DeVCV). This is the first report of a virus isolated from D. glaucum. Identification of new viruses from native plants is important, in that, they may pose a risk of transmission to other ornamental and crop plants.