The cultivated tomato (Solanum lycopersicum) is a cornerstone of global agriculture, but recent developments threaten its continued viability. Tomatoes have quite a few pests that reduce the yield and affect the appearance and value of the fruit. These circumstances present many challenges to geneticists working on creating disease-resistant varieties that would eliminate the need for chemical control methods.
Tomato brown rugose fruit virus (ToBRFV) was identified as a major new threat, capable of infecting tomato plants previously thought to be immune due to the presence of the Tm-22 gene. ToBRFV causes a range of harmful symptoms, including mosaic patterns on leaves, yellowing, and browning of fruit, and a dramatic decline in plant health and yield. Since its discovery, ToBRFV has spread rapidly to key tomato-growing regions, including Spain, Italy, China, Turkey, the United States, and Mexico, and it has demonstrated an alarming ability to overcome the Tm-22 resistance.
A BARD-funded research project has focused on understanding how ToBRFV bypasses the Tm-22 resistance and identifying potential strategies for combating the virus. Led by Prof. Moshe Lapidot of the Volcani Center (ARO) and Prof. Vitaly Citovsky of NYSU, Stony Brook, the research project aims to examine virus-host interactions across various tomato genotypes, identify specific viral factors responsible for overcoming resistance, and explore the tomato proteins involved in these interactions.
Recent findings from this collaboration have been promising. Utilizing Fluorescent in Situ Hybridization (FISH), the team was able to detect the virus in tomato reproductive tissues such as petals, ovary, stamen, style, stigma, anther, and pollen grains. Although they found no evidence of pollen transmission, it was demonstrated that ToBRFV is able to penetrate tomato pollen grains and induce germination arrest of pollen. Moreover, these results suggest that ToBRFV does not penetrate into the seeds and that the virus is seed-borne (located externally on the seed coat) in tomatoes and is transmitted mechanically from contaminated tomato seeds to the seedlings. Additionally, the researchers identified a tomato genotype with complete resistance to ToBRFV, marking a significant breakthrough in the search for resistant cultivars. This resistance appears to be governed by two interacting genes: one located on chromosome 11, responsible for tolerance, and another on chromosome 2, conferring full resistance.
As ToBRFV continues to spread, the long-term outlook for global tomato production remains uncertain, particularly for regions where the virus is already established. Researchers emphasize the need to develop new tomato varieties with inherent resistance to ToBRFV to ensure the sustainability of production in these affected areas. Without such varieties, the future of tomato farming in regions where ToBRFV has gained a foothold is at serious risk.
Moreover, the development of ToBRFV-resistant tomato plants could help reduce the reliance on chemical treatments and pesticides, offering environmental benefits and reducing the need for stringent quarantine and monitoring measures. In addition, the emergence of this virus will likely shape the direction of future tomato breeding programs, with an increased focus on breeding for resistance to ToBRFV, ensuring that tomatoes remain a resilient and reliable crop in the face of evolving viral threats.
The ongoing research offers hope for the future of tomato cultivation, with the potential to protect global production from the increasing threat of ToBRFV and similar emerging pathogens.
