Akademik Veri Yönetim Sistemi
CANADIAN JOURNAL OF PLANT PATHOLOGY, cilt.27, sa.4, ss.592-602, 2005 (SCI-Expanded)
Nucleotide sequence analysis of polymerase chain reaction (PCR)-amplified pospiviroid-related fragments in several symptomless ornamental plants indicated the presence of three distinct viroid species: Iresine viroid (IrVd), Citrus exocortis viroid (CEVd), and Chrysanthemum stunt viroid (CSVd). Primers specific to viroid species, based on partial nucleotide sequences of the viroids, were used to clone full-length genomes of the three viroids from their original host species. Viroid isolates were cloned and sequenced from the following plants: Vinca major (IrVd and CSVd), a trailing Verbena sp. (IrVd and CEVd), and a double Impatiens sp. (two CEVd). The genome sizes of these viroids ranged from 355 to 375 nucleotides. For all three viroids, rod-like secondary structures with slight variations in the CSVd and IrVd isolates from Vinca can be predicted. Nucleotide substitution at positions 163 and 211 of IrVd indicated that U-163 and A(211) were critical in maintaining the perfect rod-like conformation. Pospiviroid-specific motifs, including the loop E at the central conserved region, the terminal RY motif at the right terminal region, and the left terminal conserved region, were present in all three viroids. Inter- and intra-species phylogenetic analyses of the viroids were conducted. The implications of the phylogenetic relationship, as well as the relationship of the viroid isolates with their newly discovered hosts, confirm the observation that viroids are widely distributed in ornamental plants.