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Tomato brown rugose fruit virus in South Australia

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: Tue 20 Aug 2024
Source: Fresh Plaza [summ. Mod.DHA, edited]
https://www.freshplaza.com/oceania/article/9650978/tomato-brown-rugose-fruit-virus-detected-in-australia-s-adelaide-plains/

The tomato brown rugose fruit virus has been identified in South Australia (SA) within 2 sites on the northern Adelaide Plains. The introduction of the virus is suspected to have occurred through infected seeds, prompting an immediate response from the South Australian Department for Primary Industries (PIRSA) to form an incident management team aimed at assessing the extent of the spread and implementing containment strategies.

Containment efforts are underway, focusing on the immediate vicinity of the detected outbreaks without impacting other vegetable production in the region.

--
Communicated by:
ProMED

[_Tomato brown rugose fruit virus_ (ToBRFV) was identified as a new member of the genus _Tobamovirus_ (type member _Tobacco mosaic virus_, TMV) in Jordan and soon after in Israel (see links below). Since then, it has also been reported from various other regions worldwide (e.g., recently from India, see link below) and continues to spread. The virus was shown to affect also capsicum and has been detected in both plants and seeds of both crops. ToBRFV symptoms on tomato vary depending on host cultivar but may include chlorosis, mottling, mosaic, crinkling (rugosis) on leaves; necrotic spots on petioles and calyces; and yellowish mottling, brown spots and rugosis on fruit to make them unmarketable. On capsicum, leaf symptoms are similar; fruits may be deformed with yellow mottling or green stripes. Almost 100% incidence was reported for some outbreaks in tomato, but not every fruit on an infected plant may show symptoms.

ToBRFV (like many tobamoviruses) is seed transmitted and can also be spread by mechanical means, contaminated equipment, as well as with plant or other materials. It is very stable and can remain infectious for months outside a host. Bumblebees, which are used widely as commercial pollinators in glasshouse tomato production, have been shown to be effective vectors of ToBRFV (see link below). Volunteer crop plants and solanaceous weed species are likely pathogen reservoirs. The Tm-22 resistance gene used in some tomato cultivars to protect from other tobamoviruses (such as _Tomato mosaic virus_) does not appear to be effective against ToBRFV. Disease management relies mainly on exclusion but may include phytosanitation (disinfecting tools, removing crop debris) and control of virus reservoirs. Use of certified clean seeds or crop transplants is crucial. Research on possible seed treatments to eliminate the virus is being carried out (see link below). Tomato seeds are traded widely and are known to pose a risk of spreading viruses and other pathogens internationally (e.g., ProMED post 20140122.2222560).

Coinfection of ToBRFV with _Pepino mosaic virus_ (genus _Potexvirus_) and _Tomato spotted wilt virus_ (TSWV; genus _Orthotospovirus_) has been found in tomato (ProMED posts 20191029.6751082, 20200507.7307615), as well as with TSWV in capsicum (see link below). Other coinfecting partners may be expected, with _Peru tomato mosaic virus_ suspected (_Potyvirus_; ProMED post 20240124.8714440). It is thought that respective symptoms in coinfections may be due to either virus or synergism. Further research is needed to clarify a potential role of ToBRFV in coinfections and to determine whether its presence in coinfections may have led to earlier cases of misdiagnosis and delayed identification of this new virus.

In the reports above and the additional links below, no information can be found on how ToBRFV has been identified in SA. Because symptoms can be variable, especially if other viruses may also be present, they are unreliable for diagnosis. The virus had previously been suspected to be present in Australian tomato seed, but this was considered an unreliable record (see link below). Confirmation of the outbreak by molecular means is crucial. In the meantime, movement of host material (including seed, fruits, plants) between Australian states and to New Zealand has been stopped (see additional stories below) and biosecurity measures have been implemented in the region.

Pictures
ToBRFV on tomato:
https://gd.eppo.int/media/data/taxon/T/TOBRFV/pics/1024x0/4137.jpg and
https://gd.eppo.int/media/data/taxon/T/TOBRFV/pics/1024x0/4138.jpg
ToBRFV symptoms on capsicum:
https://agriculture.vic.gov.au/__data/assets/image/0009/555759/TOBRFV_figure-5.jpg

Links
Additional news stories:
https://www.rnz.co.nz/news/country/525846/biosecurity-ramped-up-amid-aussie-tomatoe-virus-outbreak,
https://www.hortidaily.com/article/9651792/biosecurity-new-zealand-imposes-restrictions-in-response-to-south- australian-tomato-virus-find/ (Corr.SB),
https://www.abc.net.au/news/rural/2024-08-20/tomato-brown-rugose-fruit-virus-detected-adelaide-plains/104243436 (Corr.MO),
https://www.pir.sa.gov.au/alerts_news_events/news/biosecurity/tomato_brown_rugose_fruit_virus_detected_in_south_australia (Corr.MO),
https://www.agriculture.gov.au/biosecurity-trade/export/controlled-goods/plants-plant-products/ian/2024/2024-54 (Corr.MO) and
https://www.rnz.co.nz/news/national/525904/extremely-infectious-tomato-virus-raises-fears-for-nz-growers (Corr.MO)
Information and characterisation of ToBRFV:
https://gd.eppo.int/taxon/TOBRFV (with distribution and host list),
https://doi.org/10.1007/s00705-015-2677-7,
https://doi.org/10.1007/s42161-023-01436-8 (TSWV co-infection, capsicum) and via
https://www.semanticscholar.org/topic/Tomato-brown-rugose-fruit-virus/3579397
ToBRFV suspected in Australian seed:
https://gd.eppo.int/reporting/article-7016 (unreliable record)
ToBRFV spread:
https://doi.org/10.1094/PDIS-11-23-2413-PDN (new reservoir hosts),
https://doi.org/10.1371/journal.pone.0282441 (new reservoir hosts) and
https://doi.org/10.1371/journal.pone.0210871 (by pollinators)
Tomato resistance breeding:
https://www.hortidaily.com/article/9544570/intermediate-resistance-ir-to-tobrfv-in-tomato-varieties-confirmed/
ToBRFV seed treatment:
https://doi.org/10.1007/s10658-020-02151-1
International spread of tobamoviruses by seeds (review):
https://doi.org/10.5772/intechopen.70244
Virus taxonomy via:
https://ictv.global/taxonomy
- Mod.DHA

ProMED map:
South Australia, Australia: https://promedmail.org/promed-post?place=8718377,286]