Tobacco ringspot virus Found in the Cardboard Cycad (Zamia furfuracea) in Florida.

Zamia furfuracea (Zamiaceae) is native of coastal Mexico. It is a popular houseplant and easy to grow outdoors in warm climates. In November 2005, a plant of Z. furfuracea, originally from Texas, was received at the Division of Plant Industry in Gainesville, FL. The plant had numerous chlorotic spots on the leaves that eventually became necrotic. Leaves were ground in phosphate buffer (pH 7.2) with Carborundum and used to inoculate a host range that included Chenopodium amaranticolor, C. quinoa, Gomphrena globosa, Datura stramonium, and Nicotiana benthamiana. Systemic symptoms were seen in C. quinoa (necrotic lesions), G. globosa (stunting), D. stramonium (chlorotic ringspots), and N. benthamiana (wavy line patterns) 1 to 2 weeks after inoculation. C. amaranticolor showed only small necrotic local lesions. In further host range studies, systemic infections of Beta vulgaris, D. metaloides, Lactuca sativa, N. clevelandii, Pisum sativus, Petunia hybrida, Zinnia elegans (symptomless), and Cucumis sativa were observed. However, no infection of Zea mays, Verbena hybrida, Glycine max, Phaseolus vulgaris, Catharanthus roseus, Arachis hypogaea, Trifolium spp., Vigna unguiculata, Vicia faba or Digitalis spp. was detected. Inclusions observed in leaf strips of N. benthamiana and D. stramonium indicated a possible infection of this plant with a nepovirus (1). A 337-bp fragment was amplified from total RNA isolated from an inoculated D. stramonium using reverse transcription-PCR with nepovirus group primers provided by Agdia Inc. (Elkhart, IN). Sequence analysis indicated that the nucleotide (nt) and deduced amino acid (aa) sequences of the fragment were 89 to 91% and 91 to 95% identical, respectively, to sequences of the RNA-dependent RNA polymerase gene for Tobacco ringspot virus (TRSV) contained in GenBank (Accession Nos. U50869 and AJ698718). This region was only 50% (nt) and 38% (aa) identical to Cycas necrotic stunt virus (GenBank Accession No. NC_003791), a nepovirus previously reported to infect cycads (2). The original plant, symptomatic inoculated hosts, and the symptomless zinnia tested positive by double-antibody sandwich-ELISA using commercially available antiserum for TRSV (Agdia, Inc.), further confirming the presence of TRSV. Although the virus infecting Z. furfuracea has a more restricted host range than that reported for TRSV, the serology and gene sequence indicates that this virus is a unique isolate of TRSV. References: (1) J. R. Edwardson and R. G. Christie. University of Florida, Institute of Food and Agricultural Sciences, Bull. 894. 1996. (2) S. S. Han et al. Arch. Virol. 147:2207, 2002.