Field evaluation of ToBRFV-resistant tomato cultivars under severe infection pressure

Abstract: Tomato brown rugose fruit virus (ToBRFV) poses a major threat to global tomato
production, leading to the rapid development and commercialisation of resistant cultivars.
While these cultivars have shown promising resistance under controlled conditions, their
performance under prolonged and high infection pressure in commercial greenhouse
environments remains uncertain. This study evaluated several ToBRFV-resistant tomato
cultivars under severe infection pressure at a commercial greenhouse in Belgium following an
accidental outbreak in a neighbouring susceptible crop. Crop assessments were conducted
throughout the production cycle, focusing on symptom expression and viral accumulation.
Resistant cultivars initially showed reduced or no symptom incidence and lower viral loads
compared to the susceptible control. However, a gradual increase in viral accumulation and
symptom expression was observed in some cultivars over time, suggesting partial resistance
breakdown under continuous virus pressure. Genome analyses revealed the presence of viral
mutations in later stages of the crop cycle, indicating potential viral adaptation. These findings demonstrate that resistant cultivars can significantly reduce yield losses but do not provide complete protection, emphasizing the importance of integrated disease management and longterm evaluation of resistance durability.