In June 2019, leaf samples from hybrid tomato were collected from four regions in Fayoum and Ismailia Governorates, Egypt. Twenty samples were collected from plants with viral symptoms and nine from asymptomatic plants. The diseased samples had mosaics, deformation and necrosis on the leaves (Fig. 1), and discoloration and deformations on fruits
Samples were tested by DAS-ELISA (LOEWE®, Germany) for the presence of viruses that induce similar symptoms on tomato plants. Of the diseased samples, six tested positive forTomato brown rugose fruit virus (ToBRFV) antisera, and three samples had a mixed infection with TSWV and ToBRFV. The ToBRFV antisera gave a weak cross reaction with ToMV.
Figure 1: Leaves tomato naturally infected with Tomato brown rugose fruit virus
Figure 2: Fruit of tomato naturally infected with Tomato brown rugose fruit virus
Four ToBRFV isolates were purified and sequenced in both directions. The partial nucleotide sequence of these isolates was determined and submitted to GenBank The nucleotide sequence for the Egyptian isolates shared 92.2-94.4% identity with tomato isolates from Palestine, Germany, United Kingdom, Israel, Jordan, Italy and Mexico, and a pepper isolate from Jordan. A phylogenetic tree (Fig. 3) revealed genetic variability between Egyptian isolates and isolates from different countries.
This is the first report of ToBRFV infecting tomato in Egypt and the ease with which it is mechanically transmitted may explain its rapid emergence around the world.
Figure 3: Phylogenetic tree based on partial nucleotide sequences of RNA-dependent RNA polymerase region of Tomato brown rugose fruit virus isolates from GenBank and four Egyptian isolates (Eg1-4). Bootstrap values generated from 1000 iterations indicated on the tree.
Source:
Amer MA, Mahmoud SY, 2020. First report of Tomato brown rugose fruit virus on tomato in Egypt. New Disease Reports 41, 24. [http://dx.doi.org/10.5197/j.2044-0588.2020.041.024]
Read more about the research at the BSPP New Disease Reports (M.A. Amer and S.Y. Mahmoud)