Fig. 2

Representative disease responses of the two mapping population parents and their F₁ progeny. a Resistant reaction of B. thunbergii accession ‘BtUCONN1’, showing no visual symptoms; b Susceptible reaction of B. vulgaris accession ‘Wagon Hill’, showing dense pycnia on the upper leaf surface and prolific, well-developed aecia on the lower surface; c Resistant reaction (score of 1 on the four-point scale) of B. ×ottawensis progeny ‘WH15–039’, showing sparse flecking; d Moderate resistant reaction (score 2) of B. ×ottawensis progeny ‘WH15–063’, showing evident necrotic lesions and some pycnia formation; e Moderate susceptible reaction (score 3) of B. ×ottawensis progeny ‘WH15–128’, showing well-developed pycnia and aecia, alongside sparse necrotic lesions; and f Susceptible reaction (score 4) of B. ×ottawensis progeny ‘WH15–149’, showing well-developed pycnia and aecia and no evident necrosis. All photos were taken 14 days post-inoculation