Effect of row orientation, trellis type, shoot and bunch position on the variability of Sauvignon Blanc (Vitis viniferaL.) juice composition

Background and Aims Variation in grape berry composition around the mean has seldom been studied in its own right. From the perspective of the researcher and the viticulturist, increased variation requires greater replication to achieve good estimates of composition. Bunch position on the vine, berry position on the bunch and/or vine location in the vineyard may all contribute to differences in composition (TSS, titratable acidity, pH and malic acid) between berries. Our aim was to understand how variation may be influenced by maturity, row orientation and vine training. Methods and Results Berries were sampled regularly to study the effect of harvest time, training system, row orientation and position of fruit in the canopy on Sauvignon Blanc fruit composition. Variance, skewness (symmetry) and kurtosis (range about the mean) reduced as fruit ripened. Bunch position on a shoot contributed to >60% of the variance at harvest. Conclusions Differences in berry TSS at harvest largely reflected the date of flowering. The least mature bunches at harvest were generally the secondary bunches on basal shoots; the most mature were primary bunches on distal (Scott-Henry trained) or mid-cane (vertical shoot positioned trained) shoots. Differences in leaf area : fruit mass ratio per shoot had little effect on TSS between bunches. Significance of the Study Changes in berry population distribution as the fruit ripen have implications on the interpretation of experimental results from field trials. For convenience, experiments are harvested on a single date; however, our data clearly demonstrate differences in the population of berries at different times as fruit ripen and may be obscured by sampling strategies.