Prayer plants (Maranta spp.), which are indigenous to Brazil, are commercially produced in nurseries mainly to be sold as potted houseplants. However, in frost-free areas, they are also used as a ground cover. In March 2009, the Division of Plant Industry in Gainesville, FL received cuttings of red-veined prayer plant or red maranta (Maranta leuconeura erythroneura) from several nurseries in central Florida. The cuttings originated in Costa Rica. The presence of a viral infection was indicated by the mosaic pattern seen on the upper surface of the leaves and chlorotic lesions on the underside of leaves. Epidermal strips were taken and stained in Orange-Green (O-G) and Azure A (1). Microscopic examination revealed viral inclusions that stained only in O-G, indicating the presence of a potyvirus. Leaf dips were prepared for the electron microscope and flexuous rods consistent with a potyvirus were found. Indirect-ELISA using universal potyvirus antiserum (Agdia Inc., Elkhart, IN) confirmed the presence of a potyvirus infection. Total RNA was extracted from symptomatic tissue of five infected samples with Qiagen's RNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). Reverse transcription was conducted with the oligo d(T) primer M4T with AMV-RT at 37°C for 1 h. PCR was performed with primer M4 and a degenerate primer designed to amplify the 3′ end of all potyviruses (2). A target amplicon of 1.7 kb was produced from all five samples. Three of these samples were cloned and sequenced. Approximately 1,250 bp were sequenced from each sample. The sequenced regions include the 3′ end of the Nib gene, the complete coat protein, and the beginning of the 3′ untranslated region (UTR). The nucleotide (nt) sequences were deposited into GenBank (Accession Nos. GQ853403--GQ853405). The nt sequences of the three samples were 97 to 98% identical to each other. When compared with other potyviruses in the GenBank, the samples showed closest nt identity, 92 to 93%, with several isolates of Sugarcane mosaic virus (AJ278405, AY836523, U57357, and U57356). Of the plant species mechanically inoculated (Chenopodium amaranticolor, C. quinoa, Datura stramonium, Gomphrena globosa, Nicotiana benthamiana, and Zea mays), only Z. mays (corn) showed symptoms (a mild mosaic). The same type of viral inclusions were seen in leaf strips of infected corn as in the Maranta. The corn plant reacted positively in direct-ELISA against antiserum to Sugarcane mosaic virus (Agdia Inc.). Cuttings of infected Maranta were observed in the greenhouse and indoor situations for several months. The plants infected with Sugarcane mosaic virus lacked vigor and most eventually died. ELISA tests done on a few surviving plants were positive for Sugarcane mosaic virus, but the results were inconsistent, indicating a possible low titer of virus in the plants as they were dying. To our knowledge, this is a new host for Sugarcane mosaic virus, but it does not appear that Maranta will become a significant new reservoir of this virus for sugarcane or corn growers. However, infected cuttings can greatly decrease the production of this plant as an ornamental.
References: (1) J. R. Edwardson and R. G. Christie. Univ. Fla. Inst. Food Agric. Sci. Bull. 894, 1966. (2) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997.
