Location: National Germplasm Resources LaboratoryTitle: Characterization of three new viruses of the family Betaflexiviridae associated with camellia ringspot disease
|LIU, HUAWEI - China Agricultural University|
|WU, LIPING - Nanchang University|
|ZHENG, LUPING - Fujian Agricultural & Forestry University|
|CAO, MENGJI - Southwest University|
Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2019
Publication Date: 8/22/2019
Citation: Liu, H., Wu, L., Zheng, L., Cao, M., Li, R. 2019. Characterization of three new viruses of the family Betaflexiviridae associated with camellia ringspot disease. Virus Research. https://doi.org/10.1016/j.virusres.2019.197668.
Interpretive Summary: Ornamental camellias (Camellia spp.) are a group of woody landscape plants grown around the world for their colorful flowers. In this study, three new viruses were identified in a camellia tree with foliar ringspot symptoms using a sensitive sequencing technology. Analyses of the genetic information shows that they represent three novel viruses in the betaflexivirus group. The viruses were detected in camellia trees growing in a community garden and in plants purchased from a retail nursery. This is the first study associating viruses with camellia ringspot disease. The study provides the information necessary to classify the viruses, and to help develop detection methods for further studies of the disease.
Technical Abstract: Foliar chlorotic and necrotic ringspots of different sizes were observed in many ornamental camellia (Camellia spp.) species and cultivars with or without variegation symptoms. In negatively stained preparations from three symptomatic cultivars of C. japonica, virus particles appeared as filaments with approximately 680-780 nm in length. Total RNAs of a camellia tree (C. japonica) with foliar ringspots were subjected to high-throughput sequencing (HTS). The Blast search revealed the presence of five large viral contigs, three with the highest sequence similarities to Caucasus prunus virus (CPrV, Prunevirus, Betaflexiviridae) and two with the highest sequence similarities to Cherry virus A (CVA, Capillovirus, Betaflexiviridae). Complete genome sequences of five virus isolates were determined. Sequence analyses show that these five isolates represent three novel viruses, two in the genus Prunevirus, one in the genus Capillovirus. The genome organization of the CPrV-like camellia viruses resembles that of pruneviruses but does not contain the nucleic acid-binding protein (NB) at the 3’-terminal region. They share 66.5-66.8% with each other and 51.9-58.6% with the known pruneviruses at the genomic sequence level. The genome of the CVA-like virus contains an additional NB at the 3’-terminus when compared to those of Capillovirus. The genomes of the two CVA-like virus isolates are 72.7% identical to each other and 42.1-48.4% to the known capilloviruses. Phylogenetic analyses also support these viruses are the members of either Prunevirus or Capillovirus. The two new pruneviruses are tentatively named as Camellia ringspot associated virus 1 (CRSaV-1) and CRSaV-2, and the new capillovirus is named as CRSaV-3. Infections of these viruses were common in camellia species, cultivars and hybrids. The viruses were detected in seedlings from two camellia trees, indicating that they are seed transmissible.