Sap-direct RT-PCR for the rapid detection of coleus blumei viroids of the genus Coleviroid from natural host plants

A simple and fast sap-direct RT-PCR (reverse transcription-polymerase chain reaction) for the rapid detection of 3 viroids of the genus Coleviroid is presented. The templates for cDNA synthesis were obtained directly from the sap of coleus using a pipettor, a common tool in molecular biology laboratories, and 3 coleus blumei viroids (CbVds) were detected simultaneously using a pair of universal primers designed according to sequences in the central conserved region (CCR) of CbVds. RT-PCR results demonstrated that CbVd-1, CbVd-5, and CbVd-6 can be detected accurately in viroid-infected plants but not in viroid-free plants. The results of RT-PCR, dot-blot, sequencing, and batch-detection revealed that this method can be used to identify CbVds rapidly. The method also reduces cross-contamination among different samples to a minimum. It is considered that this rapid and simple technique is an effective method for the identification and cloning of CbVds.