Detection of Citrus exocortis viroid on Solanum jasminoides plantlets from an Austrian nursery

In September 2009, thirty plantlets of Solanum jasminoides were received from a commercial nursery in Upper Austria. The material originated from a breeding company in Germany for growing-on and propagating before reselling. The plantlets did not show any symptoms of a disease and were routinely tested for Potato spindle tuber viroid (PSTVd). Leaf samples were randomly taken from several plantlets and total RNA was extracted with a commercial RNA extraction kit (RNeasy Plant Mini Kit, Qiagen, Hilden, Germany), according to the manufacturer’s instructions. A one-step reverse transcription (RT)-PCR (Qiagen, Hilden, Germany) was performed for the pospiviroid generic detection using Pospi1 primers (Verhoeven et al., 2004). In parallel a RT-PCR was carried out for the detection of PSTVd with the primers published by Shamoul et al., (1997). The generic pospiviroid RT-PCR yielded an amplicon of expected size. However, no PCR product was obtained for PSTVd.

Sequencing of the Pospi1 amplicon (partial sequence) showed a 97% identity with those of two Citrus exocortis viroid (CEVd) isolates from S. jasminoides (GenBank Accession Nos. AM920649 and AM774357). Total RNA was further tested with specific primers to CEVd (Önelge, 1997) and the full genome length (374 bp) was sequenced (GU300810), which exhibited 98% identity with those CEVd isolates previously mentioned. The mismatches were on four positions: an insertion at base 49 and substitutions at bases 72, 73 and 131 compared to AM920649 sequence; and substitutions at the positions 73, 131, 316 and 318 compared to the AM774357 sequence. This is the first report of CEVd on S. jasminoides in Austria, although this pathogen had been already described occurring in S. jasminoides in other European countries (Verhoeven et al., 2008). Results suggest the potential risk of symptomless infection of ornamental Solanaceae by CEVd as a source of infection for crop plants, and the urgency of measures to be taken to control disease spread.