A viroid from Brunfelsia undulata closely related to the Columnea latent viroid.

A viroid was isolated from symptomless Brunfelsia undulata plants using the bidirectional PAGE method for analysis of small circular RNA molecules. The viroid was transmitted to tomato by mechanical inoculation. Infected tomato plants developed symptoms similar to those caused by intermediate strains of potato spindle tuber viroid (PSTVd). Cloning and sequencing revealed that the viroid from Brunfelsia undulata is closely related to the Columnea latent viroid (CLVd). Therefore, the new viroid sequence variant has been named CLVd-B. The Brunfelsia viroid CLVd-B consists of 373 nucleotides, 215 G + C, 158 A + U with a GC content of 57.6%. The most stable rod-like secondary structure of this viroid has 80 G:C, 39 A:U and 11 G:U base pairs with a minimum free energy of -157.2 kcal/mol (-657.1 kJ/mol). The sequence similarity of the right terminal domain of CLVd-B and of tomato apical stunt viroid (TASVd) is higher than the sequence similarity of these domains comparing CLVd and TASVd.