Source: HortiDaily [abridged, edited]
In June 2019, leaf samples from hybrid tomato were collected from 4 regions in Fayoum and Ismailia governorates, Egypt. Twenty samples were collected from plants with viral symptoms and 9 from asymptomatic plants. The diseased samples had mosaics, deformation, and necrosis on the leaves, and discoloration and deformations on fruits.
Samples were tested by DAS-ELISA. Of the diseased samples, 4 tested positive for _Tomato spotted wilt virus_ (TSWV), 3 each for _Pepino mosaic virus_ and _Tomato mosaic virus_ (ToMV), 2 for _Tomato chlorosis virus_, and 6 for _Tomato brown rugose fruit virus_ (ToBRFV). Three samples had a mixed infection with TSWV and ToBRFV. Four ToBRFV isolates were sequenced and shared 92.2-94.4% identity with tomato isolates from Palestine, Germany, United Kingdom, Israel, Jordan, Italy, and Mexico, and a pepper [capsicum] isolate from Jordan.
This is the 1st report of ToBRFV in Egypt. The ease with which it is mechanically transmitted may explain its rapid emergence around the world.
[Source paper: https://www.ndrs.org.uk/article.php?id=041024]
[_Tomato brown rugose fruit virus_ (ToBRFV) was identified as a new member of genus _Tobamovirus_ (type member _Tobacco mosaic virus_, TMV) in Jordan after a new disease of glasshouse tomatoes occurred there in 2015. Since then, it is also being reported from other regions and was shown to affect also capsicum crops. It is spreading in Europe and has recently been added to the EPPO (European Plant Protection Organisation) alert list. ToBRFV symptoms on tomato vary depending on host cultivar, but they may include chlorosis, mottling, mosaic, and crinkling (rugosis) on leaves; necrotic spots on petioles and calyces; yellowish mottling, brown spots, and rugosis on fruit, making 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, by contaminated equipment, as well as with plant or other materials. It is very stable and can remain infectious for months outside a host. Recently, 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 tomato transplants is crucial. Tomato seeds are traded widely and are known to pose a risk for spreading viruses and other pathogens internationally (for example, ProMED-mail post 20140122.2222560).
Coinfection of ToBRFV with the potexvirus _Pepino mosaic virus_ has been shown earlier (ProMED-mail post 20191029.6751082), and it was thought that the observed symptoms on tomatoes may have been due to either virus or to synergism. The coinfection with TSWV reported above appears to be a new finding. Further research is needed to clarify a potential role of ToBRFV in coinfections and to whether its presence in coinfections may have led to earlier cases of misdiagnosis and delayed identification of this new virus. In the case of Egypt, a disease of uncertain cause associated with imported tomato seed (ProMED-mail post 20181012.6086559) was thought to be due to a leaf curl virus. However, in the light of the report above, a possible involvement of ToBRFV now seems to be an alternative possibility.
http://mapsof.net/egypt/egypt-map1 (with governorates)
ToBRFV symptoms on tomato:
https://www.ndrs.org.uk/article.php?id=041020 and via
Information and characterisation of ToBRFV:
https://gd.eppo.int/taxon/TOBRFV (with distribution map),
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0170429 and via
ToBRFV spread by pollinators:
International spread of tobamoviruses by seeds (review):
Virus taxonomy via: