Resistance to powdery mildew (Blumeria graminis f.sp. avenae) in oat seedlings and adult plants

In this work, 165 Avena sativa and Avena byzantina accessions were screened for resistance to powdery mildew caused by Blumeria graminis f.sp. avenae and the defence mechanisms of resistant plants were further characterized. Ten resistant and moderately resistant accessions were selected according to macroscopic assessment. A detailed histological study of selected genotypes showed a range of defence mechanisms, acting alone or in combination, that impeded fungal development at different stages. Since the resistance observed in the collection was scarce, a study of adult plant resistance was carried out in 45 genotypes selected from field trials. Nine oat landraces and two commercial varieties showed very high levels of adult plant resistance. A detailed study of the components of the adult plant resistance revealed a high increase of penetration and post‐haustorial resistance in the fifth compared to the first leaves. Identification of the resistance sources and characterization of underlying defence mechanisms will be useful for future breeding programmes and for further cellular and molecular studies to unravel the genetic basis of resistance, in this species in particular and in cereal–powdery mildew interactions in general.