New Weed Hosts for Tomato Brown Rugose Fruit Virus in Wild Mediterranean Vegetation

Tomato brown rugose fruit virus (ToBRFV; genus, Tobamovirus, family, Virgaviridae) wasfirst reported in 2015 infecting tomatoes grown under protected cropping in the Jordan Valley. Sincethen, ToBRFV has been detected in tomatoes grown in both protected and open fields across Jordan.The increased incidence of ToBRFV prompted this investigation of the potential role of naturalweed hosts in the dissemination of ToBRFV. A survey was conducted in the Jordan Valley andhighlands to determine possible reservoir hosts of ToBRFV in fields and greenhouse complexes inwhich tomatoes were grown. Detection of ToBRFV infection was made by double-antibody sandwichenzyme-linked immunosorbent assay (DAS-ELISA) and further confirmation by reverse-transcriptionpolymerase chain reaction (RT-PCR), followed by DNA cloning and sequencing, and bioassays.Thirty weed species belonging to twenty-six genera from sixteen families were tested. Twelve speciesbelonging to eight families were infected of which ten species are newly reported hosts for ToBRFV.Seed transmission of ToBRFV in Solanum nigrum was confirmed in a grow-out experiment. To ourknowledge, this is the first report of the natural occurrence of ToBRFV on weed hosts. Identificationof natural reservoirs of ToBRFV can help to develop management practices focused on weed plantspecies to prevent ToBRFV transmission. The extent to which ToBRFV survives in diverse alternateweed host species outside tomato growing seasons in different world regions requires further researchin order to establish the risk associated with the possible contribution of weeds as a reservoir forprimary infections in tomato crops.