Authors
J. Th. J. Verhoeven,
M. Botermans, and
J. W. Roenhorst, Plant Protection Service, P.O. Box 9102, 6700 HC Wageningen, the Netherlands; and
J. Westerhof and
E. T. M. Meekes, Naktuinbouw, P.O. Box 40, 2370 AA Roelofarendsveen, the Netherlands
Since the recent identification of Potato spindle tuber viroid (PSTVd) in vegetatively propagated ornamental plant species (4), many growers have asked to have their mother plants tested for this viroid. In December of 2007, a grower from Turkey submitted cuttings of cape gooseberry (Physalis peruviana) to be tested for PSTVd. Initial testing by real-time reverse transcription (RT)-PCR according to Boonham et al. (1) indicated the presence of either Mexican papita viroid, PSTVd, or Tomato chlorotic dwarf viroid in four samples. To identify the viroid(s) present, isolated RNA from these samples was used for RT-PCR (2), and products of the expected full genome size for the three viroids were amplified from each sample. One of the PCR products was sequenced (GenBank Accession No. EU862230) and analysis of the 357 nt sequence indicated it was most related to PSTVd sequences belonging to the so-called ‘Oceanian’ strain of the viroid (3), with 99.7% identity to GenBank Accession No. AY962324. Therefore, the viroid was identified as PSTVd. Pathogenicity of this PSTVd genotype was demonstrated when 4 weeks after mechanical inoculation with sap extracts seedlings of tomato cv. Money-maker showed the expected viroid symptoms of chlorosis and stunting, and the presence of the viroid in these plants was confirmed by RT-PCR (2). In March of 2008, by use of RT-PCR (2) and sequencing of the PCR product (GenBank Accession No. EU862231), PSTVd was identified in young seedlings of P. peruviana from a German grower. The German isolate differed at only three nucleotide positions from the Turkish isolate. The identification of PSTVd in young seedlings indicates that seeds had been source of infection, whereas in the case of the PSTVd infected cuttings from Turkey, the infection originated from infected mother plants. To our knowledge, these are the first reports of PSTVd in P. peruviana. Although infected P. peruviana plants did not show symptoms, they might act as sources of inoculum for crops like potato and tomato, which may suffer serious damage.
References: (1) N. Boonham et al. J. Virol. Methods 116:139, 2004. (2) A. M. Shamloul et al. Can. J. Plant Pathol. 19:89, 1997. (3) J. Th. J. Verhoeven et al. Eur. J. Plant Pathol. 110:823, 2004. (4) J. Th. J. Verhoeven et al. Plant Pathol. 57:399, 2008.
