DETECTION AND CHARACTERIZATION OF TWO PREVIOUSLY UNDESCRIBED POTYVIRUSES IN THE TERRESTRIAL ORCHID SPIRANTHES CERNUA
Spiranthes cernua is a terrestrial orchid that grows in moist areas in the southeastern US. Cultivated varieties are now also being used as flowering perennials. We have previously reported Dasheen mosaic virus (DsMV-Sc) infection in commercially-grown plants exhibiting chlorotic blotching and/or mosaic symptoms. Other similarly symptomatic plants were, however, ELISA negative using DsMV polyclonal antisera, yet gave a positive reaction with the broad-spectrum potyvirus monoclonal antibody PTY 1, an antibody specific for a highly conserved site in the potyviral coat protein. Total RNA extracts from infected leaves were used in RT-PCR assays with generic potyvirus-specific primers which amplify various highly conserved 335, c.700, or c.1600bp fragments from the 3 terminus of most potyviruses which includes the 3' non-coding region (3'NCR) and the potyviral coat protein (CP). The PCR amplified fragments were subsequently cloned and sequenced and compared to the corresponding regions of other potyviruses. This analysis revealed the presence of two unique sets of potyviral sequences, neither of which had any significant identity with each other (56% CP identity and 39% 3'NCR identity), nor with DsMV (49-53% CP, 33-43% 3'NCR), nor with any other potyvirus sequence (<64% CP identity and <57% 3'NCR identity) currently in the GenBank database, including other orchid-infecting potyviruses. Pairwise alignments and Clustal W analysis of the coat protein amino acid sequences and 3 NCR regions confirm the classification of these two viruses as new potyvirus members. We have tentatively named these two new potyviruses Spiranthes mosaic virus (SpiMV) 2 and SpiMV 3. This is only the second report of any virus infection in the genus Spiranthes and the first report of two new potyviruses infecting a member of the Orchidaceae.
Guaragna, M.A., Ndum, O. and Jordan, R. (2006). DETECTION AND CHARACTERIZATION OF TWO PREVIOUSLY UNDESCRIBED POTYVIRUSES IN THE TERRESTRIAL ORCHID SPIRANTHES CERNUA. Acta Hortic. 722, 209-218
Spiranthes mosaic virus, Dasheen mosaic virus, PCR, monoclonal antibody