Vallota mosaic virus infecting nerine in the UK

Leaves from a nerine plant (Nerine sarniensis 'Stephanie'; family Amaryllidaceae) were received at CSL for testing in 2005. The plant had been grown without obvious symptoms in Denby, England for 6 years but in the final year had developed chlorotic leaf lesions, suggestive of a virus infection.

The sample was examined for virus infection and the presence of a potyvirus was identified by both transmission electron microscopy (flexuous particles ca. 700-800 nm in length) and plate-trapped ELISA, using a broad-spectrum potyvirus monoclonal antiserum (AS-0573; DSMZ, Germany). To identify the virus species, a 1539 bp product was amplified by RT-PCR using generic primers (Gibbs & Mackenzie, 1996) and sequenced (GenBank Acc. No. EF507688). The nt sequence obtained included part of the NIb gene, the entire coat protein gene and the complete 3' untranslated region (UTR). The sequence, shared the highest identity (98%) with a partial nt sequence published for the potyvirus species Vallota mosaic virus (ValMV; EF441726). The deduced coat protein amino acid sequence of the UK isolate was also aligned and shown to be more than 98% identical to the corresponding ValMV cp sequence.

Following this identification, a further 14 nerine samples, all showing symptoms of virus infection, were screened for the presence of ValMV by RT-PCR using specific primers: nerineF 5'-GTC TCA CCA AGC GCT CGA ATG TGA TG-3' and nerineR 5'-CGC TTT CAT TTG GAT GTG TGC TTC-3'. Ten samples gave a PCR product approximating to the expected size (994 bp). Positive samples were found in a range of cultivars derived from nerine species (N. sarniensis and N. bowdenii) and hybrids (N. sarniensis/bowdenii). To confirm the identity of the virus detected by RT-PCR, amplicons from two samples (N. sarniensis 'Corusca Major' and 'Joan') were sequenced and shown to be isolates of ValMV (data not shown).

ValMV was first described in Vallota speciosa from The Netherlands (Inouye & Hakkaart, 1980). An isolate of ValMV was identified in Cyrtanthus elatus in the USA and sequenced (unpublished; Acc. No. EF441726). This is the first report of ValMV infecting nerine.