Phenotypes of detached barley leaves non-inoculated (healthy) and inoculated with Blumeria graminis f.sp. hordei (Bgh) of near-isogenic lines cv. Ingrid (WT, Mla12 and mlo3) 0, 3, 6, 10 and 14 dai, on phyto agar. Non-inoculated leaves of the genotypes showed natural senescence over the experimental period. First characteristic powdery mildew pustules became visible 6 dai on inoculated leaves of the susceptible WT and the near-isogenic line Mla12. The resistant near-isogenic mlo3 leaves did not show any powdery mildew symptoms. Senescence of inoculated near-isogenic mlo3 leaves was delayed until 14 dai. Images were taken with a digital camera (EOS 6D, Canon, Tokio, Japan) and a 100 mm object lens (EF Lens Ultrasonic EF 100 mm 1:2.8 L Macro IS USM, Canon, Tokio, Japan).