First Report of Lilac ring mottle virus Infecting Lilac in the United States

In May 2015, the Oregon Department of Agriculture investigated a report of potential virus symptoms being observed on lilac plants (Syringa vulgaris L.) produced by a nursery in Marion County. Simultaneously, symptomatic lilac plant samples were received by the Oregon State University Plant Clinic from a customer of the same nursery. Lilac ‘President Grevy’ plants inspected at the nursery showed symptoms of leaf deformation, reduction in leaf size, ring spots, and line patterns (Fig. 1). Two months later, similar foliar symptoms were observed on lilac ‘Krasavitsa Moskvy’ plants at the same nursery (Fig. 2). Symptoms on both cultivars resembled those reported for Lilac ring mottle virus (LiRMoV) (Van Der Meer et al. 1976). LiRMoV is an isometric RNA virus within the family Bromoviridae and genus Ilarvirus (Scott and Ge 1995; Scott and Zimmerman 2008) and has only been reported from the Netherlands. The virus was sap transmissible to herbaceous hosts under experimental conditions and was seed transmissible in the experimental hosts Chenopodium quinoa, C. amaranticolor, and Celosia argentea (Van der Meer et al. 1976). Symptom expression in infected lilac is influenced by environmental conditions and may be erratic; thus, infections may remain cryptic for years (Van der Meer et al. 1976). To determine if LiRMoV was present in the symptomatic lilacs, total nucleic acids (TNA) were extracted from symptomatic leaf tissues using a procedure modified from Hughes and Galau (1988). The TNA was used in ONE-STEP PCR reactions (Qiagen, Germantown, MD) at a melting temperature of 55°C and with primers (downstream: 5′-GAGACCGAAGTCTTCTTCC-3′ and upstream: 5′-CCACGTGCTTCTCACCC-3′) specific for the movement protein of the RNA3 of LiRMoV (GenBank Accession No. U17391) (Scott and Zimmerman 2008). In addition to the TNA from the samples, a positive control (plasmid pLRMV-7) (Scott and Zimmerman 2008) and negative controls (healthy plant tissue and water) were analyzed in concurrent PCR reactions. The anticipated 649-bp amplicon was produced in the lilac samples and in the positive control, but not in the negative controls. The amplicons from seven lilac samples were cloned using the pGemT Easy Vector (Promega, Madison, WI), selected by blue-white screening, and then sequenced using the primer M13F. The contiguous sequence generated was deposited into GenBank (Accession No. KX090269). Six of the seven clones contained an FIGURE 1 Foliar symptoms caused by Lilac ring mottle virus on lilac ‘President Grevy.’