Symptom development and viral accumulation in plants infected with Cucumber mosaic virus (CMV) and CMV‐2blm. (A) CMV‐2blm only induced severe disease symptoms in plants harbouring RDR6‐deficient mutations, including rdr6, rdr1/6, rdr2/6 and rdr1/2/6, but not in wild‐type, rdr1, rdr2 and rdr1/2 plants. Seedlings were photographed at 21 days after inoculation with purified CMV or CMV‐2blm viruses at a concentration of 20 μg/mL. (B) Accumulation of viral genomic RNA in systemically infected leaves of wild‐type and mutant plants infected with CMV or CMV‐2blm. Methylene blue‐stained rRNA was used as a loading control. It should be noted that 5 μg and 2 μg of total RNAs were used for the Northern blot analyses of CMV‐2blm and wild‐type CMV viral RNAs. wt, wild‐type.