Effect of pruning system, cane size and season on inflorescence primordia initiation and inflorescence architecture of Vitis vinifera L. Sauvignon Blanc

Background and Aims: Inflorescence numbers per shoot and their size vary between seasons and may, within a season, be affected by pruning systems, bud position along a cane and the size of the cane. A grapevine inflorescence typically has a main rachis and a tendril, which may or may not have flowers (an outer arm). The aim of this study was to identify the effect of these factors during inflorescence primordia (IP) initiation on the resulting number of inflorescences per shoot and their architecture. Methods and Results: Two-cane, four-cane and spur-pruned Sauvignon Blanc vines were used to investigate changes in inflorescence number, distribution and architecture over two growing seasons. The pruning system had no effect on the inflorescence number per shoot (fruitfulness), inflorescence architecture or distribution at a given cane node number. There were differences in inflorescence number and structure between the seasons, likely associated with air temperatures during primordia initiation. A warmer initiation period was associated with an increase in the occurrence of flowers on the outer arm and lower positions of the basal inflorescences (shoot bud position). An increase in cane cross-sectional area correlated to an increase in fruitfulness and an increase in the average occurrence of an outer arm with flowers along a cane. Conclusions: Inflorescence number, the position of the basal inflorescence on the developing shoot and the development of the outer arm are affected by the bud position of the shoot along a cane, the cross-sectional area of the cane and the season. Our results suggest that initiation of IP may occur at the same time for all bud positions along a shoot, so long as they are free from inhibiting factors. Significance of the Study: Cane selection can be used to modify inflorescence number and architecture and thus the potential yield of grapevines