First report of soybean mosaic virus in <i>Glycine max</i> in the United Kingdom

In August 2023 a sample of Glycine max (soyabean) was submitted to Fera Science Ltd. from a grower in eastern England, via the Processors and Growers Research Organisation. The sample was sent in following the appearance of mosaic, necrotic spots and necrosis of the leaf margin (Figs. 1-3). Diseased plants occurred in patches across the field. Nucleic acid was extracted from the sample using a Qiagen RNeasy Plant mini kit, with optional DNase step, and tested by high throughput sequencing (HTS) to identify viruses present in the sample (Fowkes et al., 2021). Analysis of the obtained sequence data revealed soybean mosaic virus (SMV) in the sample, with 2.8% (69,717) of the total read pairs sequenced (2,492,752) attributed to SMV with an average coverage of 2,885. The obtained sequence (GenBank Accession No. PQ465173) covered the full coding sequence and had 99% identity to SMV isolate “Green Shell” (MW822168.1). Metagenomic data were submitted to the Sequence Read Archive, available under SRR30598214. The same extract was used to confirm the finding of SMV using RT-PCR for potyvirus (van der Vlugt et al., 1999); the obtained product (PQ465174) had 100% identity to MW822168.1. SMV has been reported to be both seed-borne and non-persistently transmitted by aphids (Hajimorad et al., 2018). A sub-sample of 1,000 seeds from the remaining seed that had been planted tested negative for potyvirus by plate trap ELISA (DSMZ, Germany) and RT-PCR (van der Vlugt et al., 1999). Analysis of the sequence obtained by HTS shows that the aphid transmission motifs KLSC, PTK and DAG (amino acid positions 361–364, 617–619 and 2811–2813, respectively), are all present suggesting that this isolate has the potential to be spread by aphids (Hajimorad et al., 2018; Gadhave et al., 2020). With this information, it is not possible to determine whether the SMV detection originated from a low incidence in the planted seed, or if it the virus was transmitted into the crop from the wider environment. Additionally, the plant sample was examined for fungal and bacterial pathogens. No primary plant pathogenic bacteria were detected. Based on incubation and isolation Alternaria sp., Botrytis cinerea, Fusarium spp., Phoma sp. and Stemphylium sp. were identified. However, no further work was performed to identify whether any were casual agents of the symptoms seen. As this was a mixed infection of both virus and fungal agents it is impossible to determine a causal association between the agents present with the symptoms observed or the potential impact on yield. Soyabean is grown for use as an alternative protein source for human consumption and animal feed, as a legume it can also be used within crop rotations for nitrogen fixing. Currently, Europe imports the majority of its soyabean from the United States of America, but the potential economic and agronomic benefits are leading to increases in European production (Coleman et al., 2021). To the best of our knowledge, this is the first report of SMV in the UK. The predicted increase in UK soyabean production and lack of knowledge about which diseases are present on this commodity crop (Coleman et al., 2021) suggests the need for surveillance to understand the pathogen presence baseline. This work was partially funded under the Defra-Fera Long Term Service Agreement.