Assessment of tomato cultivar resistance to tomato brown rugose fruit virus and tomato spotted wilt virus

Context Tomato productivity is increasingly threatened by viral pathogens, particularly tomato brown rugose fruit virus (ToBRFV) and tomato spotted wilt virus (TSWV), which overcome classical resistance genes and cause severe yield losses. Aims This study evaluated the leaf-level tolerance responses of 10 commercially grown tomato cultivars from the Czech Republic to ToBRFV and TSWV under controlled greenhouse conditions, on the basis of leaf symptom expression and virus accumulation in leaves. Methods Viral accumulation in leaf tissue was quantified by reverse-transcription quantitative polymerase chain reaction. Cultivars were screened for resistance-associated markers (Tm-1, Tm-2 and Tm-22 for ToBRFV; Sw5, Sw5b and Sw7 for TSWV). Defence responses were assessed by expression analysis of PAL, HQT, NBR1a, WRKY33a, PR-1 and ATG7 at 21 days post-inoculation. Results Viral titres varied markedly among cultivars. Stupické polní rané and Vilma consistently exhibited reduced ToBRFV accumulation (2.3–4.2 × 106 copies), whereas Gallant and Odat showed high ToBRFV accumulation in leaves (>2.0 × 107 copies). For TSWV, Stupické polní rané exhibited a more tolerant leaf response, associated with the presence of the Sw7 allele, whereas Start, Gallant and Perun showed the least favourable leaf-level responses. None of the cultivars carried classical Tm resistance alleles for ToBRFV. Reduced viral accumulation was associated with enhanced induction of phenylpropanoid (PAL, HQT) and immune-related (NBR1a, WRKY33a, PR-1 and ATG7) genes. Conclusions Stupické polní rané and Vilma displayed the highest leaf-level tolerance (reduced symptoms and/or reduced leaf virus accumulation). Cultivar responses and defence activation varied widely among commercial cultivars. Implications These results support molecularly informed breeding strategies, focusing on gene stacking and novel resistance sources to achieve durable, improved outcomes against both viruses.