Ultrastructural and Histochemical Studies on Mildew of Barley (Erysiphe graminis DC. f. sp. hordei Marchal)

Fifth leaves of the barley cultivar ‘Osiris’ with adult plant resistance against powdery mildew were inoculated with Erysiphe graminis f. sp. hordei. Samples were taken at 32 hours after inoculation for cytochemical treatments and electron microscopy. Deposition of gold‐labelled wheat germ lectin was detected in the wall of the haustorial neck of the fungus and in an outer layer of a papilla, indicating the presence of oligomers of N‐acetylglucosamine. Con A binding was detected mainly, in a middle layer of a papilla, demonstrating the presence of α‐bound glucose and/or mannose. Treatment with PA‐TSH‐SP revealed glycosubstances with vicinal hydroxyl groups present mainly in an outer layer of another type of papilla. Pretreatment with, protease before PA‐TSH‐SP staining resulted in a positive Thiery reaction in spherical structures of a papilla, indicating that vicinal hydroxyl groups were exposed to staining after removal of protein from these structures.