"Developing ToBRFV resistant cultivars is the most viable and sustainable solution", says Dr. Yasin Topcu, one of the tomato breeders at the Republic of Türkiye Ministry of Agriculture and Forestry Batı Akdeniz Agricultural Research Institute in Antalya, Turkey. He and his colleagues are at the forefront of resistance breeding. As part of a recent large-scale international effort, they are tapping into the rich genetic diversity of wild tomato species to combat Tomato Brown Rugose Fruit Virus (ToBRFV).
Right: Dr. Yasin Topcu
Highly contagious
Since the emergence of ToBRFV in 2014-2015 (Jordan and Israel), ToBRFV has rapidly spread across continents, infiltrating major tomato-producing countries including the USA, Mexico, Italy, the Netherlands, China, Turkey, and beyond. ToBRFV is highly contagious and can be mechanically transmitted via hands, tools, plant debris, or even pollinators like bumblebees.
Its ability to overcome the most commonly used resistance gene, Tm-22, once considered the gold standard in Tobamovirus resistance, making it a nightmare for breeders and growers alike", Yasin explains. "Its impact is visible and severe: plants exhibit mosaic patterns, narrowing and bubbling of leaves, and most critically, brown rugose (wrinkled) patches on fruits, leading to major post-harvest losses and rejection in fresh markets. ToBRFV doesn't just reduce yield — it destroys market value."
Right: A picture from a local market in Antalya/Turkey. ToBRFV-affected fruits are sold at local markets at the lowest price since these affected fruits can not be exported
Viable and sustainable
With nearly all commercial tomato varieties susceptible and limited tools available for managing viral diseases, the team at the Batı Akdeniz Research Institute is confident that developing resistant cultivars is now the most viable and sustainable solution.
The team sees that despite varieties being introduced as resistant, the levels of resistance differ greatly. In their studies, the team tested commercial F1 Hybrids sold in Turkey as resistant to ToBRFV. "It is obvious that many varieties currently on the market are not yet fully resistant at the desired levels, and that virus-related problems will increase in the future and cause even bigger problems. It is of great importance for large and small companies to pay more attention to this issue in their R&D studies in order to eliminate possible problems in the future. It should not be forgotten that the resistant varieties to be developed will have a very large market not only in Turkey but also in the world and will increase the prestige of Turkey", the team says.
Tomato Breeding Team: Dr. Serkan Aydin, Dr. Yasin Topcu, Halim Can Kayikci
The susceptible commercial hybrids are showing typical ToBRFV symptoms, including discoloration and deformation.
The susceptible commercial hybrids are showing typical ToBRFV symptoms, including brown rugose patterns
Resistance
So, resistance it is – and that's where the Batı Akdeniz tomato breeding team has put their efforts. Yasin explains how the story of resistance to tobamoviruses has long involved wild tomatoes. "S. habrochaites, S. peruvianum, and S. pimpinellifolium, among others, have historically provided resistance genes like Tm-1, Tm-2, and Tm-22. But ToBRFV has rewritten the rulebook. These once-reliable genes now fall short—even under standard temperature conditions."
Still, hope is not lost, the recent research shows. As part of a recent large-scale international effort, they are tapping into the rich genetic diversity of wild tomato species to combat Tomato Brown Rugose Fruit Virus (ToBRFV). Yasin explains that these screening efforts focus on evaluating thousands of accessions sourced from major gene banks—most notably the Tomato Genetics Resource Center (TGRC) at UC Davis, the USDA Plant Genetic Resource Unit in Geneva, NY, and the BATEM tomato gene bank. "The goal is to identify novel sources of resistance and tolerance to ToBRFV, which can be utilized in breeding programs. The wild germplasm includes species such as S. habrochaites, S. peruvianum, S. chilense, S. ochranthum, and S. pimpinellifolium. So far, we have screened more than 1000 accessions from these species. "
The fruits of the Solanum pimpinellifolium accession, utilized as a source of resistance
The fruits of the Solanum pimpinellifolium accession, utilized as a source of resistance
A Solanum pimpinellifolium accession growth habit
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Left: ToBRFV-affected fruits exhibit noticeable symptoms such as discoloration and deformation. Right: The fruits of the accessions, screened as sources of resistance
By combining phenotypic screening with molecular tools, BATEM's tomato breeding team aims to discover genetic loci and develop DNA markers for marker-assisted selection. "These tools are essential to accelerate the breeding of ToBRFV-resistant tomato cultivars and ensure long-term crop protection. Identifying and utilizing novel resistance from wild species is key to staying ahead of evolving viral threats like ToBRFV."