Influence of training system on the reproductive development and hormonal levels of Vitis vinifera L. cv. Tempranillo

Grapevine training systems affect fruit composition due to the effects of microclimate on fruit ripening. However, recent studies have shown that hormone levels (especially polyamines) have an essential role in grapevine floral initiation and fruit set. The objective of this study was to determine the influence of two training systems on grapevine leaf physiology and hormone concentrations (abscisic acid and polyamines) and their relationships with yield and fruit quality in Tempranillo grapevines grown under field conditions. Leaf water status, leaf gas exchange, berry respiration, polyamines in leaves, flowers, and berries, abscisic acid in flowers and berries, and yield and fruit composition at harvest were measured in cordon- and head-trained vines. All measurements were made at four developmental stages: flowering, green berry, veraison, and end of ripening (harvest). Head-trained vines had higher CO 2 assimilation rate and stomatal conductance than cordon-trained vines at the end of the reproductive cycle (veraison and harvest). Head-trained berries also had higher total polyamine content and free-to-bound polyamine ratio than cordon-trained vines at veraison and harvest. Abscisic acid in berries showed an increase at veraison in both training systems and was higher in head-trained vines than in cordon-trained vines. Head-trained vines had lower yields but higher fruit quality at harvest, mainly due to a higher total soluble solids (Brix). Results indicated that training system particularly affected the hormonal content of berries, which may have affected yield and fruit composition.