Seasonal changes in the relative expression levels of (a) VvINV (VIT_09s0002g02320), (b) VvGIN2 (VIT_02s0154g00090), (c) VvSUSY4 (VIT_11s0016g00470), (d) miR396 (inset) and its target VvGRF5 (VIT_16s0039g01450) and (e) miR156 (inset) and its target VvExp‐8 (VIT_13s0067g02930) measured by quantitative reverse transcription‐polymerase chain reaction (RT‐PCR) in grapevine virus B (GVB)‐free (full line, filled circles) and GVB‐infected (broken line, filled squares) leaves. Data are mean values and bars are standard error (SE) (n = 3). Asterisks denote significant differences attested by two‐tailed Student’s t‐test (P < 0.05).