UK: First report of Rose spring dwarf-associated virus in Rosa spp.

In July 2019, a sample of Rosa spp. was submitted to Fera Science Ltd. via the Royal Horticultural Society (RHS) gardening advice service. The sample (ID220) was sent in following the appearance of unknown symptoms including mottling, yellow/white patching, thin texture and a pink colour in the leaves.

RNA was extracted using a CTAB method adapted from Adams et al. (2009), with the 4M LiCl incubation performed overnight at 4°C. The sample was tested for common rose viruses using RT-qPCR (Table 1). A positive result was achieved for Rose cryptic virus 1. Subsequently, the sample was analysed by high throughput sequencing (HTS) using a TruSeq Stranded Total RNA Library Prep Plant kit (Illumina Inc., USA) for library preparation. A MiSeq instrument and a MiSeq Reagent Kit v3 (600-cycle) (Illumina Inc.) were used to run the library. The run generated 569,452 reads for the sample, and data was analysed as described by Fox et al. (2019). Three fragments of rose spring dwarf-associated virus (RSDaV) were identified (234, 251 and 229 bp; GenBank Accession Nos. MT993839-MT993841). A BLAST+ search found sequences with high sequence identity in both nucleotide (92.11-93.59% identity, EU024678.1) and amino acid comparisons (94.34-100%, YP_001949737.1; YP_001949736.1; YP_001949738.1). RT-PCR amplification using specific primers (Salem et al., 2008) was performed to confirm the result, and a product of the expected size (418 bp) was obtained.

To assess the spread of RSDaV in the UK, 171 roses were analysed using the RT-PCR assay. Samples were collected as part of a survey of rose viruses in the UK and both asymptomatic and symptomatic leaf samples, consistent with virus infections symptoms (mottling, yellow veining, distortion, and ringspots) were included. Only one sample (ID140) resulted positive for RSDaV, and no symptoms were identified. Previous analysis showed this sample was positive for Arabis mosaic virus by ELISA and RT-qPCR.

The RT-PCR product (418 bp) from both RSDaV-positive samples (ID220, 140) were sequenced, and nucleotide comparisons showed a 98.51-99.02% identity with sequences in GenBank (HM236366.1; HM2363641; HM236362.1; HM236364.1). Amino acid comparison showed a 98.51-100% identity with previously published sequences (ADK78852.1; ADK78851.1).

RSDaV has previously been found in the USA (Salem et al., 2008), Chile (Rivera & Engel, 2010), and New Zealand (Milleza et al., 2013). This is the first report of RSDaV in Europe. Further samples (4) were submitted to the RHS and Fera Science Ltd. Plant Clinic, showing the previously described unknown symptoms. They were tested by RT-PCR and also sequenced by HTS and tested negative for RSDaV. The cause of these symptoms is not believed to be of viral origin.

Source: BSPP New Disease Reports (I. Vazquez-Iglesias, J. Scrace, S. McGreig, H. Pufal, R. Robinson, G.R.G. Clover, I.P. Adams, N. Boonham and A. Fox)

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