Symptoms and light micrographs of Arabidopsis Col‐0 and eds1 (enhanced disease susceptibility 1), pad4 (phytoalexin deficient 4), rar1 (required for Mla12 resistance) and ndr1 (non‐race‐specific disease resistance 1) mutants infected with Oidium heveae HN1106. Four‐week‐old Arabidopsis wild‐type (WT) Col‐0 and mutants were inoculated with O. heveae HN1106. (A) Symptoms were photographed at 10 days post‐inoculation (dpi). (B) Light microscopy images were taken after fungal structures had been stained with Coomassie brilliant blue at 10 dpi. Bar, 50 μm. (C) Infected leaves were stained with trypan blue at 10 dpi. Bar, 50 μm. (D) Infected leaves were stained with 3,3′‐diaminobenzidine (DAB) at 7 dpi. Bar, 50 μm. These experiments were repeated twice with similar results.