Effects of shoot girdling and/or periodic leaf removal on inflorescence primordia initiation and development inVitis vinifera L. cv. Sauvignon Blanc

Abstract

Background and Aims Inflorescence primordia (IP) development starts in the buds of leaf axils approximately 12 months before flowering. Primordia initiation progresses acropetally as the shoot develops, although little is known about the timing of initiation at different node positions up the developing shoot. Girdling and/or leaf removal treatments were used to investigate the timing of development and structure of grapevine inflorescences at different positions along the shoot. Methods and Results Individual shoots were either girdled at their base shortly after fruitset or left intact. Leaves were then removed from those shoots on four occasions from the time of girdling to natural leaf fall in the autumn. Dormant latent buds from treatment shoots (shoot node positions one to ten) were grown as single-node cuttings (SNCs) in a glasshouse, and the inflorescence number per SNC and their architecture were scored on developing shoots. Girdling fully leafed shoots increased the proportion of SNC basal inflorescences with an outer arm but had no effect on the number of inflorescences per SNC. Girdled shoots that had their leaves removed at 0 or 4 weeks post-fruitset had a decrease in inflorescence number per SNC and outer arm development from nodes six and eight, respectively. Conclusions Inflorescence initiation before node positions six and eight was complete by the time girdling and leaf removal treatments were applied, and initiation at nodes six and eight occurred at 0 and 4 weeks post-fruitset. The development of the apical IP and the outer arm of the basal IP appears to occur at the same time. Significance of the Study This study presents novel information regarding the timing of IP initiation at different positions along the developing shoot, including the initiation and development of the outer arm. Also, the formation of an outer arm is shown to be sensitive to girdling and/or leaf removal.