DETECTION, IDENTIFICATION, AND CHARACTERIZATION OF NEW AND EMERGING VIRAL AND BACTERIAL DISEASES OF ORNAMENTAL PLANTS
Location: Floral and Nursery Plants Research Unit
Title: Mixed infection and novel viruses in various species of Phlox
Submitted to: Acta Horticulture Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2009
Publication Date: August 11, 2011
Citation: Hammond, J., Reinsel, M.D. 2011. Mixed infection and novel viruses in various species of Phlox. Acta Horticulture Proceedings. 901:119-126.
Interpretive Summary: Virus infection reduces the productivity and quality of many ornamental plants, and multiple virus infections may accumulate in vegetatively propagated plants. Several viruses have been detected in samples of various species of phlox from commercial nurseries, including creeping phlox (Phlox stolonifera), sweet William phlox (P. divaricata), downy phlox (P. pilosa), pincushion phlox (P. subulata), and annual phlox (P. drummondii). As many as five distinct viruses were detected in a single plant. Three distinct, previously undescribed carlaviruses have been detected in creeping phlox (Phlox virus S), sweet William phlox (Phlox virus B), and annual phlox (Phlox virus M), and partially characterized. Two distinct potyviruses, Spiranthes mosaic virus 3 and a novel potyvirus, were detected in several phlox types. Alternanthera mosaic virus, a potexvirus, was also detected in several phlox species. Tobacco ringspot virus was detected in creeping phlox and pincushion phlox, and Angelonia flower break virus was detected in annual phlox. Methods were developed to detect and differentiate most of these viruses. Knowledge of the viruses infecting phlox, and methods for virus detection, will aid growers in the selection and production of plants free from infection.
Several species of Phlox are commonly cultivated as perennial bedding plants, and hybrid varieties of annual phlox (Phlox drummondii) have recently entered the market as vegetatively propagated pot plants. Virus-like symptoms are commonly observed in plants offered for sale. We have detected several viruses in different species of phlox, typically in mixed infections of up to five distinct viruses, using a combination of electron microscopy, host range, and broad-spectrum or virus-specific serological or polymerase chain reaction (PCR) assays. The potexvirus Alternanthera mosaic virus (AltMV) was detected in plants of creepimg phlox (P. stolonifera), sweet William phlox (P. divaricata), and downy phlox (P. pilosa). One novel carlavirus, which we have named Phlox virus S (PhlVS), was isolated from P. stolonifera; another previously undescribed carlavirus, Phlox virus B (PhlVB), was detected only in P. divaricata; a third carlavirus, Phlox virus M (PhlVM), was detected in hybrid annual phlox. Two distinct potyviruses were detected, Spiranthes mosaic virus 3 (SpiMV-3), and a previously undescribed potyvirus; both were found together in P. stolonifera ‘Blue Ridge’ and ‘Bruce’s White’, and in P. glaberrima ‘Anita Kistler’. SpiMV-3 was also detected in P. divaricata, and potyvirus isolates of as-yet-undetermined sequence were also detected in P. divaricata, P. pilosa, and P. subulata. Tobamovirus isolates were found in P. divaricata and P. subulata, Cucumber mosaic virus (CMV) in P. subulata, and Tobacco ringspot virus (TRSV) in P. stolonifera and P. subulata. Angelonia flower break virus (AnFBV, carmovirus) has been detected in hybrid annual phlox (P. drummondii) in combination with PhlVM. However, it is difficult to determine which viruses are most important, as there is little difference in symptom severity between P. stolonifera plants carrying a single virus (AltMV) and plants infected with up to five viruses (AltMV, PhlVS, TRSV, SpiV3, and a novel potyvirus).
We have determined the complete sequences of PhlVS and PhlVB, and the 3’-terminal region of PhlVM. These three viruses infect different species of phlox, are clearly distinct from each other and from previously characterized carlaviruses at both the nucleotide and amino acid level, and thus represent separate species in the genus Carlavirus.