First report of Coleus blumei viroid 5 infection in vegetatively propagated clonal coleus cv. 'Aurora black cherry' in Japan.
Coleus (Coleus blumei) cultivars with abnormal growth retardation available in domestic markets in Japan were surveyed for viroid infection. Total RNAs were extracted for analysis by 2D-PAGE. A circular RNA band corresponding to Coleus blumei viroid 1 (CbVd-1) was frequently detected in the samples examined. In addition, another circular RNA band with a size larger than that of CbVd-1 was also detected in three samples of 'Aurora black cherry', a vegetatively propagated clonal coleus cultivar. The band was excised from the gel and was subjected to cDNA amplification by RT-PCR. As a result, two specific bands were detected, a major band corresponding to CbVd-1 and a faint band with a size similar to that of CbVd-5. Therefore, new CbVd-5 specific primers were designed for amplifying the entire CbVd-5 genome. The major sequence variant (14 of 26 cDNA clones sequenced) completely matched to CbVd-5 reported in China. This is thought to be the first report of CbVd-5 infection in commercial coleus in Japan.