P. emaculata urediniospore interactions with Brachypodium. Epifluorescence micrograph showing pre-infection structures after germination of P. emaculata urediniospores (Sp) on Brachypodium (Bd21) leaf surface in the form of the oriented growth pattern of germ tubes (Gt) (a) and formation of appressoria (Ap) on stomatal (St) openings (b). (c) 3, 3’-diaminobenzidine (DAB)-stained fungal structures showing a penetration peg (Pp) originating from the appressorium that helps to push through the closed stomata for entry into the intercellular space within the host leaf. (d) Localized cell death in the form of hypersensitive (HR) response at the site of infection. (e) Scanning electron microscope (SEM) image showing the formation of pre-infection structures after urediniospore germination on the leaf surface of Brachypodium. (f) Confocal microscope image showing intercellular hyphal (Hy) growth inside mesophyll cells. (g)
Brachypodium leaf at two weeks after infection with rust urediniospores. No visible disease symptoms appeared on Brachypodium. Scale bar = 50 μm or unless specified.