First report of Tomato brown rugose fruit virus in tomato in the United Kingdom

In July 2019 a sample of tomato leaves (Solanum lycopersicon cv. Piccolo) was submitted to Fera Science Ltd, from a grower in the South of England. The sample was sent in following the appearance of mosaic symptoms, which had spread throughout the crop in the affected glasshouse. Symptoms were consistent with a viral infection and had emerged following inoculation with a mild strain of Pepino mosaic virus (PepMV) as a cross-protection treatment, however symptoms had persisted post-inoculation.

The sample was tested using ELISA kits for the presence of PepMV (Bioreba, Switzerland) plus Tobacco mosaic virus, Tomato brown rugose fruit virus (ToBRFV) and Tomato mosaic virus (DSMZ, Germany), according to the manufacturers' instructions. The sample tested positive for the presence of ToBRFV (Tobamovirus) and PepMV but negative for the other viruses. The ToBRFV result was confirmed by conventional RT-PCR using ToBRFV-specific primers ToBRFV-F/ToBRFV-R (Alkowni et al., 2019) and with generic tobamovirus primers 514 Tombamo-s1/515 Tobamo-as1 (Menzel et al., 2019). PCR products of the expected sizes (560 bp for both primer sets) were obtained, sequenced and confirmed to be ToBRFV by nucleotide sequence comparison (GenBank Accession No. MN210325 and MN210326 respectively). Genome sequences for ToBRFV and PepMV in the sample were also obtained by sequencing a TruSeq ribosome depleted plant leaf library (Illumina, UK) on a MiSeq sequencer (Illumina, UK). Sequencing and analysis were done as described previously (Adams et al., 2014). The genome of ToBRFV (MN182533) had between 99.7-99.9% identity to genomes of ToBRFV isolates from Israel (KX619418.1), Jordan (KT383474.1), Germany (MK133095.1, MK133093.1), Mexico (MK319944.1) and Palestine (MK165457.1). The genome of PepMV (MN182534) had high identity (99.6%) to that of an isolate of PepMV commonly used for cross protection (Menzel et al., 2019).

ToBRFV was first reported from symptomatic crops in Israel in 2014, with the presence of the virus being confirmed following a similar outbreak in Jordan in 2015, with recent reports from Germany (2018) and Turkey (2019) (EPPO, 2019) and China (Yan et al., 2019). The virus overcomes the tomato tobamovirus-resistance gene TM-2². Fruit from ToBRFV-infected plants are known to mature irregularly and can be mottled with yellow or brown spots making fruit unmarketable. The virus may also pose a risk to pepper crops (EPPO, 2019).

Following reporting of the presence of ToBRFV the grower voluntarily removed all plants from the affected glasshouse and destroyed these in accordance with guidance from the UK National Plant Protection Organization. Work is being conducted to investigate the possible source of the outbreak.