Tomato Brown Rugose Fruit Virus (ToBRFV)
Tomato Brown Rugose Fruit Virus (ToBRFV) is an emerging disease issue in greenhouse tomato crops worldwide. First identified in Israel in 2014, a number of outbreaks have since occurred in North America, Europe, and Asia. Natural infection of pepper and eggplant has also been reported.
ToBRFV is a member of the tobamovirus family along with tobacco mosaic (TMV), tomato mosaic (ToMV), and tomato mottle mosaic (ToMMV). ToBRFV is especially worrisome for tomato growers because it has overcome the Tm-22 gene that confers resistance to tobamoviruses in many tomato cultivars. Like TMV, ToBRFV is very stable and easily transmitted by mechanical means; in a highly managed crop such as greenhouse tomatoes, this means that human activity is the primary vector. It may also be transmitted mechanically by bumblebees employed to pollinate greenhouse crops. The virus is also seedborne. Research indicates that while the virus is most often associated with the seed coat but may occasionally be present in the endosperm. It has not been detected in the embryo. Transmission rates from seed to seedling are considered to be very low; however, a very low rate of seedling infection can still result in a large number of infected plants because the virus is easily transmitted among seedlings by mechanical means.
The virus may be transmitted from peppers to tomatoes or vice versa. There are no truly resistant tomato or pepper cultivars currently available.
Foliar symptoms of ToBRFV on tomato and pepper include deformed, crinkled leaves, mosaic, mottling, flecking, chlorosis, and/or necrosis. Fruit symptoms include discoloration and rough brown patches or ringspots. Irregular fruit shape and maturation patterns may also occur. Browning of the veins in the fruit calyx in the early stages of fruit ripening may also be observed. Symptom expression can vary widely among tomato cultivars: some may be infected but remain asymptomatic.
Management practices for ToBRFV include planting of disease free seed and seedlings, scouting plants regularly for symptoms, and discarding symptomatic plants. Strict hygiene is essential- tools and work spaces must be disinfected frequently. Recent research has demonstrated that 10% bleach is one of the most effective disinfectants. Workers should wash their hands thoroughly and frequently. If you have reason to believe that ToBRFV is active in your tomato or pepper crop, please contact the UMass Extension Plant Diagnostic Lab at 413-545-3209. Asymptomatic screening is not recommended.
On November 15th, 2019, USDA/APHIS issued an emergency federal order that calls for pre-export testing of tomato and pepper propagative material (plants, seeds, grafts, and cuttings) and fruit produced in any country where ToBRFV has been detected; to date, this list includes Israel, Jordan, Turkey, Greece, Italy, the United Kingdom, the Netherlands, China, and Mexico. Countries where ToBRFV has not been reported may state this fact by providing a letter from the nation’s plant protection organization: propagative material and fruit exported to the USA are then exempt from the testing requirement. Tomato and pepper fruit from Canada are also subject to inspection prior to export, because Canada often imports these crops from Mexico and re-exports them to the US. US Customs and Border Protection also increased inspections at U.S. ports of entry to ensure imported tomato and pepper fruit are free from symptoms of ToBRFV. This federal order is similar to the one passed in August 2019 concerning several viroids known to infect tomato.
The tobamoviruses infecting tomato are closely related and many, including ToBRFV, will elicit a positive reaction from a TMV immunostrip test.
While an outbreak of ToBRFV in the Northeast is not expected, it is important to be aware of the signs and symptoms this virus causes. See the references below for photos and further information.
University of Florida: http://blogs.ifas.ufl.edu/pestalert/2019/07/23/tomato-brown-rugose-fruit-virus/
American Seed Trade Association: https://www.betterseed.org/wp-content/uploads/ToBRFV-QA.pdf