November 12, 2025
For the past decade, tomato growers have been fighting against Tomato Brown Rugose Fruit Virus (ToBRFV). In 2020, resistant varieties hit the market, starting with varieties from Syngenta Vegetable Seeds. But five years later, how do growers navigate the dozens of companies that claim various levels of resistance to find one that works and helps them achieve their goals?
First, let’s break it down: what is the difference between High Resistance and Intermediate Resistance?
There’s no legal standard for what level of control means high or intermediate resistance – no regulatory guidance, zero. The International Seed Federation (ISF) has issued guidelines as to the different levels of resistance. Given the lack of exact metrics for high or intermediate resistance, companies can claim high or intermediate resistance using any standard – and our internal research proves not everyone has the same standards (or follow ISF guidelines adequately).
Why Syngenta Opted for IR Designation
There’s no proverbial ‘silver bullet,’ no genetics, spray, or management method is perfect and will completely stop the infestation of ToBRFV. With pressure there’s symptoms, because no one is selling total immunity.
“We took a conservative approach and consider our first trait intermediate resistance to heavy ToBRFV infestation,” said Norm Sissons, Solanaceae Crops Strategy Head. “That doesn’t mean it’s less effective, our surveys with customers and internal performance data results show competitive and effective resistance compared to competitors that claim high resistance.”
We test varieties in real-world conditions, and the real world isn’t perfect, and growers all have different levels of pressure and management styles. What might be high resistance for one grower, might only show intermediate protection for another.
Syngenta is a global company with some growers who work in high-tech greenhouses with all of the latest technologies, and we work with other growers who use greenhouses that don’t have all of the controls and tools – so the needs and demands for the trait are different.
“We're committed to continuing to support and develop additional traits with durable resistance to ToBRFV in current and future tomatoes,” Sissons explained. “All while maintaining high yield potential, superior fruit quality and taste, and long shelf life.”
ToBRFV HR Versus IR Study Results
Throughout the past year, our researchers were hard at work conducting a study comparing non-resistant checks, to commercial varieties with our current ToBRFV resistance trait, upcoming varieties with two resistance sources, and with competitors’ varieties that claim intermediate or high resistance.
The study setup:
- Artificial inoculation on the second true leaves (mechanical inoculation) - 35 days after sowing (the day following plantation).
- Evaluations three months after initial inoculation scoring plants on a one to nine scale to examine individual plant symptoms on fruits and canopy in most cases.
This study was conducted in a dedicated, contained greenhouse. The key findings indicate:
- Syngenta’s initial trait provides competitive fruit protection when compared with HR designated competitors.
- Environment and genetic background play a strong role in how effective resistance is in tomatoes.
- Combining multiple resistance traits (trials for upcoming Syngenta products expected to launch as early as 2026) shows stronger control than single traits alone and improved additional leaf protection.
- Competitors show stronger protection on the leaves compared to Syngenta’s initial trait, but show no significant difference on the fruits compared to Syngenta varieties available in the test.
We’ll provide more details and data about this study and upcoming innovations over the coming months. Visit www.syngentavegetables.com/resources/TOBRFV to learn more and find these updates.
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