First report of Tulip virus X in New Zealand

In November 2007, severe leaf mottling (Fig. 1) and flower breaking (Fig. 2) were observed in field-grown tulip plants 'Pink Diamond' near Invercargill on the South Island of New Zealand. Electron microscopy on crude sap preparations from symptomatic leaves showed flexuous, filamentous particles (approximately 530 nm in length). Symptomatic tulip plants tested positive using Tulip virus X (TVX) polyclonal antiserum in a DAS-ELISA assay (Neogen Europe Ltd, Auchincruive, UK). Total RNA was extracted from symptomatic plants and tested using broad-spectrum potexvirus primers according to the published RT-PCR cycling conditions (van der Vlugt & Berendsen, 2002). An amplicon of the expected size (735 bp) was obtained and sequenced (GenBank Acc. No. EU555190). A BLAST search in GenBank confirmed the sequence to be TVX (99% nt identity with AB066288). RNA from the plants was also tested using broad-spectrum carlavirus primers (Agdia Inc., Indiana, USA). A PCR product of 250 bp was sequenced and a BLAST search confirmed this to be Lily symptomless virus (LSV), (98% nt identity to Genbank Acc No. X15343; sequence not submitted to GenBank).

The results showed that the tulip plants were co-infected with both viruses. LSV has been recorded previously in New Zealand (Pennycook, 1989), but this is the first report of TVX in the country. Cut flowers are an increasingly important commodity in New Zealand and tulips are a significant crop. In 2006 exports of bulbs alone were worth NZ$6.6 million.