Investigations on adult plant resistance of barley against Erysiphe graminis f.sp. hordei

Spring barley cultivars and lines were tested for 3 years in field studies for adult plant resistance against Erysiphe graminis f.sp. hordei. The cultivars Osiris and Asse were selected for further detailed cytological studies and compared with the susceptible cultivar Peruvian. Under controlled greenhouse conditions, the percentage of conidia that had formed a functional haustorium and secondary hyphae (infection efficiency) was reduced in fifth leaves of the adult plant resistant cultivars. On fifth and flag leaves of adult plant resistant cultivars, papillae were formed more frequently under primary germ tubes and appressoria, and fungal penetration was prevented more often than on the susceptible cultivar Peruvian. In ultrastructural studies various types of papillae were observed, but could not be strictly correlated with penetration success or failure of the fungus.