Fig. 6

Confocal microscopy images and schematic demonstration of pycnidial development during plant infection. Susceptible wheat cultivar Drifter inoculated with the fluorescent 1E4_GFP (wild-type, left) or ΔZtSof1_GFP (right) strains were monitored by confocal microscopy at different days post-infection (dpi). For 1E4_GFP, the primary intracellular hyphae surrounding the stomatal guard cells produced specialized knots from where secondary hyphae emerge and elongate. After 9 days of infection, these secondary hyphae fuse with another nearby hypha (represented by black circles), creating an interconnected network in the sub-stomatal cavity. The combination of sub-stomatal hyphal accumulation and anastomoses generates the pre-pycnidium at 12 days, which later supports the asexual reproduction of Z. tritici. For the ΔZtSof1_GFP mutant, the filamentous hyphae kept extending as individual hyphae, and no fusion points were observed. The lack of anastomosis stops the developmental process of the pycnidium formation. For earlier time points (6, 7, and 8 dpi), please see Additional file 12: Fig. S12