MOLECULAR CHARACTERIZATION AND DETECTION OF A TRIPARTITE CRYPTIC VIRUS FROM ROSE
S. Sabanadzovic, N. Abou Ghanem-Sabanadzovic
Three dsRNA molecules with estimated molecular weights of c. 1.7, 1.5 and 1.4 kbp were extracted from a symptomless hybrid tea rose cv. Sheer Bliss, and further characterized. Analysis of complete sequences showed that they represent genome segments of a tripartite cryptic virus with the proposed name Rose cryptic virus 1 (RCV-1). All three segments were monocistronic, with the dsRNA-1 encoding a protein containing conserved motifs of RNA-dependent RNA polymerases. The two proteins encoded by dsRNA 2 and 3 shared c. 20% common amino acids and are probably involved in the make up of the viral capsid. Phylogenetic analysis based on the viral RdRp gene showed closest relationships of RCV-1 with Fragaria chiloensis cryptic virus (FCCV) and Raphanus sativus cryptic virus 2 (RsCV-2), both recently described tripartite cryptoviruses. Interestingly, this group of viruses appears to be phylogenetically closer to mycoviruses belonging in the genus Partitivirus than to plant-infecting cryptoviruses. The virus was detected by RT-PCR in ca. 30% of the tested samples belonging to different cultivars/hybrids, indicating that it may be quite common in rose germplasm.