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ISHS Acta Horticulturae 901: XII International Symposium on Virus Diseases of Ornamental Plants

MIXED INFECTIONS AND NOVEL VIRUSES IN VARIOUS SPECIES OF PHLOX

Authors:   J. Hammond, M. Reinsel
Keywords:   phlox, potexvirus, potyvirus, carlavirus, virus detection, broad spectrum PCR
DOI:   10.17660/ActaHortic.2011.901.15
Abstract:
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 creeping phlox (P. stolonifera), sweet William phlox (P. divaricate), 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. divaricate; 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. divaricate, 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. stolonifera, P. divaricate 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, SpiMV3, 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.

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