Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2014
Publication Date: 2/21/2015
Citation: Hammond, J., Reinsel, M.D. 2015. Variability in alternanthera mosaic virus isolates from different hosts. Acta Horticulturae. 1072:47-52.
Interpretive Summary: Alternanthera mosaic virus (AltMV) is an emerging plant virus that has been detected in multiple ornamental crop species representing widely divergent taxonomic families, and across multiple continents. The rapid distribution and wide host range of this virus raise questions about the potential means of spread. Examination of the variability between virus isolates can offer clues to the origin of infection, and aid application of control measures to prevent further spread. The nucleotide and deduced amino acid sequences of AltMV isolates from different ornamental plant sources were compared, and isolates were found to group into two types, respectively identified as ‘phlox-like’ and ‘portulaca-like’ based on similarity to isolates originally detected in perennial creeping phlox or portulaca. All isolates identified as ‘portulaca-like’ originated from ornamentals grown as annual bedding plants or pot plants, whereas ‘phlox-like’ isolates were obtained only from various species of perennial phlox, plus an isolate from Nandina domestica, a perennial plant. Perennial plants are typically grown in different production systems than annual bedding plants and pot plants, suggesting that AltMV transmission between crops occurs primarily within the production systems. Distinct portulaca isolates from different countries and time periods were highly similar, suggesting that portulaca may be one means of spread of AltMV between nursery production facilities. Screening stocks of portulaca to eliminate AltMV may minimize further spread of the virus to other annual and pot plant species.
Technical Abstract: We have determined the complete genome sequences of Alternanthera mosaic virus phlox isolate PA (AltMV-PA) and four infectious clone variants derived from AltMV-SP, as well as partial sequences of other isolates from various types of phlox, and from portulaca, nandina, and cineraria. Phylogenetic comparison of the amino acid sequences of the various gene products of these AltMV isolates and other AltMV sequences from GenBank reveals that there are two main groups of AltMV isolates. ‘Phlox-type’ isolates are differentiated from ‘portulaca-type’ isolates, and both are clearly distinguished from both the serologically-related Papaya mosaic virus (PapMV) and from Potato virus X (PVX). A US isolate from nandina is ‘phlox-type’, whereas isolates from hybrid annual phlox and from cineraria are ‘portulaca-type’. Partial RdRp sequences are available for several other isolates; within this partial RdRp region a New Zealand isolate from nandina is identical to AltMV-PA, whereas Brazilian isolates from torenia, and a ‘portulaca-type’ Florida isolate share several variant residues, one of which is also present in a Russian portulaca isolate. Many other residues differ between AltMV and both PapMV and PVX. These comparisons suggest that portulaca may have been the source of infection of AltMV for most ornamentals other than perennial phlox species and nandina.