First report of Alfalfa mosaic virus in eggplant in Turkey.

Abstract

Coleus (Coleus blumei) is an ornamental plant hosting several species of the genus Coleviroid [type member Coleus blumei viroid 1 (CbVd-1)], family Pospiviroidae. CbVd-3, a recognized member of the family, has only been reported from Germany in 1996 (Spieker et al., 1996). According to their proposed rod-like secondary structure, the left portion of CbVd-3 is also preserved in CbVd-2 and CbVd-6, which are viroid chimeras (Spieker, 1996; Hou et al., 2009). Fifty leaf samples of coleus, including 30 from Beijing and five each from Tianjin, Nanjing, Fujian and Hainan (China), were collected from 2009 to 2010. Low molecular weight RNAs were extracted as previously reported (Li et al., 1995). RNA extraction from viroid-free coleus was used as negative control. Results of dot-blot hybridization using DIG-labeled CbVd-3 cRNA probe and RT-PCR using CbVd-3 specific primers (PF: 5’-CGGGTACCCAGCAACCTGCT-3’; PR: 5’-TGGGTACCCGCGAAGAGC-3’) showed that one sample from Beijing and one from Hainan were positive for CbVd-3. Products of the expected size were amplified only from the hybridization-positive samples. After cloning, sequence analysis of five selected clones revealed that the similarities between the sequences we obtained and the CbVd-3 sequence reported previously (GenBank accession No. X57294) varied from 99.72% to 100%. The dominant sequence has been submitted to GenBank (accession No. HQ727548). These results provide experimental evidence that the two tested plants were infected by CbVd-3. To our knowledge, this is the first report of CbVd-3 from China and the only report of this viroid outside Germany.