First Report of Cucumber mosaic virus Infection in Pachysandra in the United States

Pachysandra terminalis Siebold & Zucc. (Japanese pachysandra, spurge) is widely used as a groundcover. In early 2012, Japanese pachysandra plants from Missouri, which originated in Pennsylvania, showed symptoms of light and dark green mosaic, leaf deformation, concentric ringspots, and stunting. Initial screening of symptomatic leaf tissue by transmission electron microscopy (TEM) using partially purified extracts confirmed the presence of spherical (~28 nm) and bacilliform (18-nm diameter, 35- to 58-nm length) virus particles. Immunosorbent electron microscopy (ISEM) using antisera to a clover isolate of Alfalfa mosaic virus (AMV) (PVAS 92) and to Cucumber mosaic virus (CMV) (ATCC PVAS-30) obtained from the American Type Culture Collection, Manassas, VA, confirmed the presence of AMV and CMV. No other type of virus-like particles were observed by TEM. After 6 months, nearly 20% of the 4,000 pachysandra cuttings exhibited the described symptoms. However, it is possible that more than 20% of the cuttings were infected with both viruses and not yet exhibiting symptoms. Reverse-transcription PCR (RT-PCR) was done using total RNA extracted with a Qiagen RNeasy kit and Ready-To-Go RT-PCR beads (GE Healthcare, UK Limited, UK). The primer pair CMV-1 (5'-GCCGTAAGCTGGATGGACCA) and CMV-2 (5'-TATGATAAGAAGCTTGTTTTCGCG) were used (3) to obtain a 502-bp amplicon from the coat protein (CP) region of CMV RNA 3. The product was ligated and cloned (pGEM-T Easy Vector System; Promega, USA). Three clones were sequenced (UMGC, USA), and the consensus sequence (Sequencher 5.1, Gene Codes Corp., USA) was deposited in GenBank (Accession No. JX227938). The sequence obtained had 100% identity with a homologous CP CMV sequence (AFQ94058) and 99% identity with several other homologous CP CMV sequences (CAX62443, CCK24369, and 15 others). It also contained an EcoRI site at nucleotides 332 to 337, characteristic of CMV Type II isolates (3). The primer pair AMV1F (5'-ATCCACCGATGCCAGCCTTA) and AMV1R (5'-TTCCGCCTCACTGCTGCTG) generated a 1,047-bp product from AMV RNA1 that was deposited in GenBank (JX227937). This product had 100% identity with a homologous AMV sequence (AFQ94057), and 99% identity with several other homologous AMV sequences (AGV15824, ADO85715, CBX36144). From the data presented here, it was concluded that the pachysandra had a mixed infection of AMV and a Type II isolate of CMV. Occurrence of AMV in pachysandra was first reported in New Jersey in 1982 (2) and reported for the first time in France and Germany in 2000 (1). The presence of CMV infection in pachysandra has not been reported in the present literature. Some of the symptoms associated with AMV infection in pachysandra in New Jersey (2) and Europe (1) were similar to the symptoms produced by pachysandra plants infected with both viruses (ring spots, mosaic, and line patterns). However, some symptoms were unique to the mixed infection in pachysandra by AMV and CMV (leaf deformation, stunting). A potential source of this co-infection could occur when plants are grown near alfalfa fields (AMV infection by aphids) and undergo vegetative propagation (CMV infection by contaminated tools). This is the first report of pachysandra co-infected by AMV and CMV in the United States. References: (1) L. Cardin and B. Moury. Plant Dis. 84:594, 2000. (2) D. E. Hershman and E. H. Varney. Plant Dis. 66:1195, 1982. (3) S. Wylie et al. Aust. J. Agric. Res. 44:41, 1993.