First report of dasheen mosaic virus infecting calla lilies in South Korea

In April 2022, leaves showing virus-like symptoms including mosaic, feathery chlorotic mottle and distortions were observed on calla lilies (Zantedeschia sp.) growing in a greenhouse in Jeolla province, South Korea. Leaf samples from nine symptomatic plants from the same greenhouse were collected and tested for Zantedeschia mosaic virus (ZaMV), Zantedeschia mild mosaic virus (ZaMMV) and Dasheen mosaic virus (DaMV) by reverse transcription-polymerase chain reaction (RT-PCR) with specific primers, ZaMV-F/R (Wei et al. 2008), ZaMMV-F/R (5'-GACGATCAGCAACAGCAGCAACAGCAGAAG-3'/5'-CTGCAAGGCTGAGATCCCGAGTAGCGAGTG-3') and DsMV-CPF/CPR, respectively. In previous surveys, ZaMV and ZaMMV were detected in calla lily fields in South Korea. Of 9 symptomatic samples, 8 were positive for ZaMV and ZaMMV but no PCR product was obtained from the ninth sample, which showed a yellow feather-like pattern. To identify the causal virus, total RNA from a leaf sample of the symptomatic calla lily was extracted using an RNeasy Plant Mini Kit (Qiagen, Germany) and analyzed by high-throughput sequencing. Ribosomal RNA was removed and a cDNA library was prepared using an Illumina TruSeq Stranded Total RNA LT Sample Prep Kit (Plants) and sequenced on an Illumina NovaSeq 6000 system (Macrogen, Korea), yielding 150 nt paired end reads. De novo assembly of the 88,171,036 reads was performed using Trinity software (r20140717) while the 113,140 initially assembled contigs were screened against the NCBI viral genome database using BLASTN. One contig of 10,007 bp (GenBank LC723667) shared 79.89-87.08% nucleotide (nt) identities to the available genomes of other DsMV isolates including Colocasia esculenta isolates Et5 (MG602227, 87.08%; Ethiopia) and CTCRI-II-14 (KT026108, 85.32%; India), and a calla lily isolate (AJ298033, 84.95%; China). No contigs representing other plant viruses were identified. To confirm the presence of DsMV, and because the virus was not detected using DsMV-CPF/CPR, RT-PCR was performed using new virus-specific primers DsMV-F/R (5'-GATGTCAACGCTGGCACCAGT-3'/5'-CAACCTAGTAGTAACGTTGGAGA-3'), designed based on the contig sequence. PCR products of the expected 600 bp were obtained from the symptomatic plant, cloned into the pGEM-T Easy Vector (Promega, USA), and two independent clones were bidirectionally sequenced (BIONEER, Korea), and shown to be identical. The sequence was deposited in GenBank as acc. no. LC723766, and shared 100% nt identity to the full-length contig LC723667, and 91.83% identity to the Chinese calla lily DsMV isolate (AJ298033). DsMV, a member of the genus Potyvitus in the family Potyviridae, is one of the major viruses infecting taro in South Korea, showing mosaic and chlorotic feathering symptoms (Kim et al. 2004); however, there is no record in the literature of the identification of this virus in South Korea in ornamental species including calla lily. To survey the sanitary status of other calla lilies, 95 samples with or without symptoms were collected from other regions and subjected to RT-PCR detection for DsMV. Ten of these samples were positive with primers DsMV-F/R, including seven mixed infections (DsMV+ZaMV or DsMV+ZaMV+ZaMMV). To our knowledge, this is the first report of DsMV infecting calla lilies in South Korea. The virus is easily spread by vegetative propagation (Babu et al. 2011) and by aphids (Reyes et al. 2006). This study will help the management of viral diseases on calla lilies in South Korea.