Real Time PCR (qRT-PCR) analysis of internode developmental gene expression. The y axis refers to the relative expression ratio between target mRNA versus the reference mRNA (polyubiquitin SCCCST2001G02.g). The relative expression levels were determined in Internode 1 and 9 tissues from a pool of the seven individuals with the highest Brix measures (HB) and the seven individuals with the lowest Brix measures (LB) of Population 2. All reactions were carried out in parallel and each reaction was performed in triplicates. Error bars were calculated as described previously . The transcript levels for the reference genes were verified to not vary in response to the treatments. The P values correspond to the probability Pr(MI>II) and Pr(MI<II) for up- and down-regulated genes, respectively when In9 and In1 samples were compared. The values of P were calculated for the HB and LB pools of plants independently. The SAS was considered differentially expressed when P ≥ 0.95.