Effect of floral cluster pruning on anthocyanin levels and anthocyanain-related gene expression in 'Houman' grape

Abstract

Lateral floral clusters were removed from the main axis of the floral clusters of 'Houman' grape plants, leaving only 3-5-cm-long region of flowers at the end of the central axis. The floral clusters were pruned at 7 days prior to flowering. The effect of the pruning on fruit quality was assessed by determining the composition and levels of anthocyanins in the fruit and anthocyanin-related gene expression. Results indicated that floral cluster pruning significantly improved the quality of the fruit by increasing berry size, fruit weight and the total content of soluble solids. Floral cluster pruning also decreased the level of titratable acidity. Sixteen different anthocyanins were detected in fruit of the pruned clusters, while only 15 were detected in fruit from unpruned clusters. The level of anthocyanins was also significantly higher in fruit of the pruned clusters than in the unpruned clusters. Anthocyanin-related gene expression was also significantly upregulated to a higher level in fruit from pruned floral clusters as compared with unpruned clusters. The upregulation was closely associated with increases in anthocyanin biosynthesis.

Figure 1

Effect of floral cluster pruning on berry diameter (a), weight (b), total soluble solid content (c) and titratable acidity content (d) at different stages of berry development (mean±s.e., n=30). '*' indicates a significant difference between treatments; *P⩽0.05.

Figure 2

HPLC chromatograms of anthocyanidins in ‘Houman’ mature grape berries obtained from pruned floral clusters (pruning) and unpruned floral clusters (control). Different peaks represent different kind of anthocyanidins.

Figure 3

Changes in the concentration of total anthocyanins and five main antyocyanidin derivatives at different stages of ‘Houman’ grape berry development. Berries were obtained from pruned and unpruned (control) floral clusters. (a) Total content. (b) Pn-derivative. (c) Pt-derivative. (d) Mv-derivative. (e) Cy-derivative. (f) Dp-derivative. (mean±s.e., n=3). '*' indicates a significant difference between treatments; *P⩽0.05.

Figure 4

Relative expression of anthyocyanin biosynthesis-realted genes at veraison in grape berries obtained from pruned and unpruned (control) floral clusters. All control data set as 1. (mean±s.e., n=3). '*' indicates a significant difference between treatments; *P⩽0.05.

Figure 5

Unpruned (a) and pruned (b) floral clusters in ‘Houman’ grape and the resulting appearance of fruit from unpruned (c) and pruned (d) floral clusters.