FIRST REPORT OF COLEUS BLUMEI VIROID IN MALAYSIA

Abstract

Plectranthus scutellarioides (synonym: Coleus blumei) is a popular home garden plant in Malaysia. It is susceptible to infection of six variants of Coleus blumei viroid (CbVd) (genus Coleviroid; family Pospiviroidae). A total of 49 samples from cultivars Saturn and Dipt in Wine showing symptoms such as dwarfing, faded color and reduction in leaf size were collected from commercial nurseries and residential areas from different states in Malaysia from February to June 2016. Total nucleic acid was extracted from the leaves and tested by RT-PCR using three sets of primers: CbVdR/CbVdF, CbVd5F/CbVd5R (Hou et al., 2009) and CbVd-1F/CbVd-1R (Chung and Choi, 2008). Altogether 39 out of 49 samples were positive to CbVd (primers CbVdR/CbVdF) (250-300 bp), CbVd-1 (primers CbVd-1F/CbVd-1R) (249 bp) and CbVd-5 (primers CbVd5F/CbVd5R) (274 bp). The amplicons of 249 bp and 274 bp from CbVd-1 and CbVd-5 specific primers, respectively, were cloned into pCR 2.1 TOPO® vector. Sequence analysis of both the 249 nt and 274 nt clones revealed 99-100% identity to CbVd-1 clone 1 (GenBank accession No. DQ178399.1) and CbVd-5 clone 1 (FJ151370.1) from China, respectively, thus confirming the presence of CbVd-1 (MF176948-51) and CbVd-5 (MF176952-55) in all of the tested samples. CbVd-1 and CbVd-5 were found together in both cultivars without particular symptom correlation. The cultivation of P. scutellarioides in Malaysia is mainly through imported seeds, which could explain the transmission of CbVd in Malaysia. To the best of our knowledge, this is the first report of CbVd-1 and -5 in Malaysia.