Fig. 1

Differential progression of Fusarium root rot during susceptible and resistant interactions. a Root phenotype of the susceptible cultivar Sumai 3 at 14 days after root inoculation (dai) with F. graminearum in comparison to healthy (control) seedlings. Besides necroses, root biomass reduction is a major impact of the disease. b Visible symptoms on roots and stem bases of Sumai 3 at 14 dai. Arrows indicate necrotic root lesions. Necrosis symptoms on the first stem segment demonstrate colonization by the pathogen. c Root phenotype of the partial resistant cultivar Florence-Aurore at 14 dai in comparison to healthy (control) seedlings. d Picture detail of Florence-Aurore seedlings showing the location of stem base measured by MS imaging (boxed area) and the root–shoot junction at seed residues (arrows). e Early stage of stem base colonization in the susceptible Sumai 3 at 7 dai. The picture detail shows hyphae growing within the abaxial epidermis of outer leaf sheath. f Advanced stem base colonization in Sumai 3 at 10 dai. g Hyphae in vascular bundle of leaf sheath obtained from Sumai 3 at 14 dai. h Stem section of Sumai 3 with infested vascular bundles at 21 dai. i Sporadic stem base colonization in partial resistant cultivar Florence-Aurore at 21 dai. j Non-fungal fluorescence signals in bundle sheath cells surrounding the stem vasculature in cv. Florence-Aurore at 14 dai. Histopathological images were generated by confocal laser scanning microscopy (e, g–k) and fluorescence microscopy (f) on WGA^® Alexa Fluor 488 stained hyphae (green signals). Abbreviations: Bs, bundle sheath cells; Co, cortex (parenchyma cells); Ep, epidermis; L1, outer leaf sheath; L2, inner leaf sheath; P, phloem; Sc, sclerenchyma; Vb, vascullar bundle; X, xylem. Scale bars: 100 µm (e, g, h, j, k); 25 µm (f, i)