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Distribution of tomato mottle mosaic virus in Europe

A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

Date: April 2023
Source: European Plant Protection Organisation (EPPO) Reporting Service 04/2023/095 [summ. Mod.DHA, edited]
https://gd.eppo.int/reporting/

_Tomato mottle mosaic virus_ (_Tobamovirus_, ToMMV- EPPO Alert List) was first described in 2013 from a tomato crop sampled in 2009 in Mexico. It was subsequently found in the Americas, Asia, and Europe causing infections on tomato and capsicum crops.

However, there are questions about the real distribution of ToMMV worldwide. Historical seed accessions of _Solanum lycopersicum_ and _Capsicum_ spp. (including wild relatives) from the collection of the Centre of Genetic Resources, the Netherlands (CGN), were tested for ToMMV by real-time RT-PCR and Illumina sequencing. Seeds had been produced in France, Spain, and the Netherlands.

Tomato seed produced in the Netherlands in 2007, in France in 2010 and 2011, as well as capsicum seed produced in Spain in 2015 and 2016 were positive for ToMMV. The results show that ToMMV has occurred in Europe before its 1st description and is possibly more widespread than currently known.

[Source publication: https://doi.org/10.1007/s10658-023-02677-0]

--
Communicated by:
ProMED

[_Tomato mottle mosaic virus_ (ToMMV; genus _Tobamovirus_) can affect tomato and capsicum, resulting in unmarketable fruits in both crops. Symptoms may include necrotic lesions, chlorosis, distortion and mottle on leaves, as well as necrosis on fruits. A disease incidence of up to 87% has been reported in tomato. The virus has also been reported in aubergine in mixed infection with _Tobacco mild green mosaic virus_, but its role in symptom development in this crop is as yet unclear. Pea (_Pisum sativum_; see ProMED post 20211021.8699190) was reported as a 1st record of a symptomatic infection in a non-solanaceous species; chickpea (_Cicer_ spp.) has been reported as an asymptomatic host. ToMMV is considered an emerging virus in Europe on tomato and capsicum, it is spreading in the region. A potential additional risk to leguminous crops also appears likely.

ToMMV is very stable and can be spread by mechanical means (human activities, insect damage, plant-to-plant contact), with contaminated agricultural tools, infected plant material (cuttings, tomato transplants, crop debris), contaminated soil, water, as well as by insect pollinators used in some commercial crops. Volunteer crop plants and solanaceous weed species are potential pathogen reservoirs. Similar to _Tomato brown rugose fruit virus_ (ToBRFV; see ProMED post 20200206.6959141), resistance genes used in some tomato cultivars to protect from other tobamoviruses, such as _Tomato mosaic virus_, do not appear to be effective against ToMMV.

Many tobamoviruses are seed transmitted; its fast international spread suggested that this is also the case for ToMMV, at least in tomato and capsicum. Capsicum and tomato seeds imported from Europe and North America for sowing have been found to be positive for ToMMV in Australia (ProMED post 20200210.6976116). While virus transmission to seedlings germinated from infected seeds remains to be confirmed, the evidence for its presence on or in commercial seed confirms the potential of introducing the virus to new areas in this manner.

For some tobamovirus species, seed coat surface sterilisation is effective in preventing transmission to new seedlings, suggesting that these viruses are carried on the outside of seeds. However, for some species such as _Cucumber green mottle mosaic virus_ (see previous ProMED posts in the archives), surface sterilisation of seeds does not seem to prevent transmission, suggesting these viruses may be carried within the endosperm, since seed-transmitted tobamoviruses are thought to be absent from embryos.

Disease management of tobamoviruses relies mainly on exclusion, but may include phytosanitation (disinfecting of tools, removal of crop debris) and control of weed reservoirs. Use of certified clean seeds or seedling transplants is crucial. Among the seed-borne viruses, tobamoviruses are currently considered a risk for crop production worldwide due to increasing global seed trade.

Maps
Europe, overview:
https://mapofeurope.com/wp-content/uploads/2018/03/europe-political-map.jpg and
https://promedmail.org/promed-post?place=8710104,6010

Pictures
ToMMV symptoms on tomato:
https://pliki.sadyogrody.pl/i/02/74/31/027431_620.jpg,
https://www.warzywapolowe.pl/wp-content/uploads/2020/07/tomato_mottle_mosaic_virus_2klOWfqWibGpC785HlXs.jpg, and
https://www.warzywapolowe.pl/wp-content/uploads/2020/07/tomato_mottle_mosaic_virus_1klOWfqWibGpC785HlXs-696x406.jpg

Links
Information on ToMMV:
https://gd.eppo.int/taxon/TOMMV0,
https://www.eppo.int/ACTIVITIES/plant_quarantine/alert_list_viruses/tomato_mottle_mosaic_virus,
https://www.agriculture.gov.au/import/goods/plant-products/seeds-for-sowing/emergency-measures-tommv-qa,
https://doi.org/10.1094/PDIS-10-16-1504-RE, and
https://doi.org/10.1186/s12985-016-0676-2
Research on host resistances:
https://gd.eppo.int/reporting/article-7578 and
https://doi.org/10.1016/j.jia.2022.07.020
International spread of tobamoviruses by seeds (review):
https://www.researchgate.net/publication/321639141_Seed_Transmission_of_Tobamoviruses_Aspects_of_Global_Disease_Distribution
Virus taxonomy via:
https://talk.ictvonline.org/taxonomy/
EPPO alert list:
https://www.eppo.int/ACTIVITIES/plant_quarantine/alert_list
- Mod.DHA]