Cucumber mosaic virus (CMV) has a reported host range of 750 to 1,200 species (2,3) that includes weeds, wild plants, crops, and ornamentals. Two new CMV hosts were recently identified in Florida. In July 2011, leaves of Odontonema cuspidatum (firespike), a member of the Acanthaceae, with virus-like symptoms were sent to FDACS-DPI. Firespike is an ornamental shrub native to Mexico with evergreen ovate leaves tapering to a pointed tip. Leaf symptoms included severe leaf distortion with some subtle yellowing or mosaic on younger leaves. Pink-red crystals were seen in leaf strips stained with the nucleic acid stain Azure A, indicating a viral infection. In January 2012, leaves of Psychotria punctata (dotted wild coffee), a member of the Rubiaceae, with virus-like symptoms were sent to FDACS-DPI. Dotted wild coffee is a small exotic tropical tree found in south Florida with many tiny leaf nodules inhabited by endosymbiotic bacteria. In addition to the nodules, these leaves had many large dark green ringspots surrounded with a yellow halo. Both samples were positive for CMV when tested with ImmunoStrips and/or by conventional ELISA using CMV antiserum (Agdia, Elkhart, IN). To confirm CMV infection, reverse transcriptase (RT)-PCR on total RNA from a leaf sample of each plant species was used with previously published cucumovirus primers (1). An expected ~940 bp product was amplified from each sample and cloned into pGEM-T (Promega, Madison, WI). Ten clones from each plant species were sequenced in both directions. After removal of primer sequences, the 906 bp products were 96.3% identical with each other and showed 96.8 to 98.9% nucleotide identity with CMV sequences from Hungary, the United States, and Austria (GenBank Accession Nos. AF517802, U20668, and HQ916354, respectively). Identification of CMV infection in these two species expands the known host range and therefore the reservoir of this plant virus. This has implications for the ornamental industry in general and Florida farmers in particular.
References: (1) S. K. Choi et al. J. Virol. Methods 83:67, 1999. (2) E. J. Sikora. Cucumber Mosaic Virus, Pant Disease Notes, Alabama Cooperative Extensions System, retrieved online at http://www.aces.edu/pubs/docs/A/ANR-0868/ANR-0868.pdf, 2004. (3) T. A. Zitter and J. F. Murphy. The Plant Health Instructor. DOI: 10.1094/PHI-I-2009-0518-01, 2009.