Susceptibility to the powdery mildew fungus. A, Wild-type (WT), GFP-rop6DN (ROP6DN), GFP-rop6DN with low GFP-rop6DN expression and weak phenotype (ROP6DN wild-type), SA biosynthesis mutants eds1-2, sid2-1, and sid2-2, and double mutants of GFP-rop6DN with sid2-1 (ROP6DN sid2-1) and with the SA signaling mutant npr1-2 (ROP6DN npr1-2) plants are susceptible to the powdery mildew fungal pathogen G. orontii. B, Fungal entry rates of G. orontii on GFP-rop6DN (6DN) and into GFP-rop6DN plants with low expression levels and weak phenotype (6DN WT) are lower compared with the entry rate on wild-type, GFP-ROP6 (R6), and GFP-rop6CA (6CA) plants. C, Fungal entry rates of Bgh on GFP-rop6DN (6DN) and on GFP-rop6DN plants with low expression levels and weak phenotype (6DN WT) are higher compared with the entry rate on wild-type, GFP-ROP6 (R6), and GFP-rop6CA (6CA) plants. The entry rates of Bgh on the GFP-rop6CA plants are higher than on wild-type and GFP-ROP6 plants. D, G. orontii conidiospore formation was significantly lower on GFP-rop6DN (6DN), GFP-rop6DN sid2-1 (6DN sid2-1), and GFP-rop6DN npr1-2 (6DN npr1-2) compared with wild-type and GFP-rop6DN WT (6DN WT) plants. Conidiospore formation was strongly enhanced compared with the wild type on eds1-2 and slightly enhanced on sid2-1 and sid2-2
SA biosynthesis mutants. E, Treatments with the SA analog BTH (black bars) reduced G. orontii conidiospore formation and further enhanced resistance of GFP-rop6DN plants. Gray bars show mock-treated (water) plants.