Differences between low- and high-SB berry groups in (A) seed weight-to-berry weight ratio (SB), (B) sugar level and visual observation, and (C) seed tannin level at two- and one-week prevéraison, and at mid-véraison (MV) cluster stages. The data represent the berries selected for downstream hormone and expression analyses based upon their highest SB differential. Error bars are ± SEM (n = 5). In panel B, the ripening phenotype of the berries of low and high-SB groups were indicated as dark green (green hard immature phase), light green (green soft phase with sugar increase), and red (red colored advanced ripening phase). The data representing low and high-SB berry populations are described in Additional file 3. Significant differences between low and high-SB at each cluster stage are indicated by asterisks (Student’s t-test, p < 0.05). Significant differences of each SB group between the ripening stages are denoted by different letters (lower and upper case letters are used for low and high-SB berries, respectively (Tukey’s HSD, p < 0.05)).