© 2004 Plant Management Network.
Canna yellow mottle virus Detected in Canna in Florida
M. Timur Momol, University of Florida, IFAS, Department of Plant Pathology, North Florida Research and Education Center, Quincy 32351; Benham E. L. Lockhart, University of Minnesota, Department of Plant Pathology, St. Paul 55108; Hank Dankers, University of Florida, IFAS, North Florida Research and Education Center, Quincy, FL 32351; and Scott Adkins, USDA-ARS-USHRL, Fort Pierce 34945
Corresponding author: Timur (Tim) Momol. firstname.lastname@example.org
Momol, M. T., Lockhart, B. E. L., Dankers, H., Adkins, S. 2004. Canna yellow mottle virus detected in canna in Florida. Online. Plant Health Progress doi:10.1094/PHP-2004-0809-01-HN.
Cannas are herbaceous flowering plants native to the tropics and subtropics. They are widely cultivated as ornamentals in Florida although their precise economic value to the nursery industry is not documented. The occurrence of a yellow mottle disease of canna (Canna indica) characterized by veinal necrosis and mottling, and caused by a small non-enveloped bacilliform virus, Canna yellow mottle virus (CaYMV), was first reported in North America in 1988 in Minnesota (3). This virus represents a species of the genus Badnavirus in the Caulimoviridae.
Symptoms similar to this disease were observed in outdoor and greenhouse-grown canna plants in Florida in the spring of 2003 and winter of 2004, respectively. Symptoms included foliar chlorotic and necrotic mottle and veinal streaking (Fig. 1). The incidence of symptomatic canna was more than 60% (~18,000 symptomatic potted plants) in the same nursery in both years.
Partially purified extracts from symptomatic leaves were examined by electron microscopy (EM) and by immunosorbent electron microscopy (ISEM) as described previously (1) using a broad-spectrum antiserum raised against a mixture of Sugarcane bacilliform virus and Banana streak virus isolates (5). Typical badnavirus-like particles were observed in extracts from symptomatic (Fig. 2) but not from asymptomatic canna plants.
The presence of CaYMV in symptomatic plants was confirmed by PCR amplification using CaYMV-specific primers CaYMV-3 and CaMYV-4. These primers were derived from the sequence of an ~1.4 kb PCR product previously amplified from CaYMV virion DNA using degenerate primers BADNA T and BADNA 2 (4, Lockhart unpublished data). The priming sites are located in two conserved regions of the badnavirus genome, the tRNAmet binding site in the intergenic region and the reverse transcriptase (RT) domain in ORF III, respectively. The sequence of the forward primer (CaYMV-3) was 5’- GAC TTC CTG GGT GCA ACA AT -3’ and the sequence of the reverse primer (CaMYV-4) was 5’- TCT GTG CAA TCT TGG CGT AG -3’. These CaYMV-specific primers amplified a PCR product (Fig. 3) of the predicted size (565 bp) from total DNA extracted from infected plants using a Plant DNeasy Mini Kit (Qiagen, Inc., Valencia, CA). No PCR product was obtained from equivalent DNA extracts from asymptomatic plants.
To determine if the PCR products were amplified from the CaYMV genome, they were purified using a QIAquick PCR purification kit (Qiagen, Inc.) and cloned using a Qiagen PCR CloningPlus kit (Qiagen, Inc.). Clones were screened by PCR for the presence of an ~565 bp insert. Five PCR-positive clones were sequenced bidirectionally and the edited sequences were compared to that of the original CaYMV genomic sequence. The nucleotide sequences of the five clones obtained from symptomatic cannas were > 99.5% identical to each other and to the original CaYMV genomic sequence. These results confirm the identity of CaYMV in these canna samples.
Based on symptoms, EM, ISEM, PCR, and sequence analysis it is concluded that CaYMV, previously reported in Japan (6) and in Minnesota, USA (3), is also present in Florida. There is no known vector for this virus (3). This disease is distinct from canna mosaic, which is caused by an aphid-transmitted virus (2). Current recommendations for management of this virus in cannas are to destroy plants with typical symptoms and to use only virus-free rhizomes (which can be indexed by PCR) for propagation. Canna yellow mottle can be an economically important disease constraint on the production of cannas in Florida.
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