Gallic acid, sinapic acid and catechin as potential chemical markers of Vitis graft success

Abstract The lack of graft success is a problem that causes economic loss to nursery growers and wine growers, especially because it is often expressed when the vineyard is already established. Grafting is a complex phenomenon, involving anatomical, physiological, biochemical and molecular interactions between the scion and the rootstock. For this reason, the lack of graft success is a complex problem to study. However, it is believed that through a joint analysis of the different mechanisms of graft success, one can advance more quickly in the knowledge of this phenomenon. Despite the scarce information available on the role of phenolic compounds in Vitis grafts, an analytical method was developed and validated for phenolic compounds quantification in vine graft tissues reviling some chemical markers for the cv. ‘Syrah’ with 110R and SO4 rootstocks. This work aims to determine, among phenolic acids and two flavanols, the chemical markers of graft compatibility between scions from two clones of cv. ‘Touriga Nacional’ (TN 21 and TN 112) and the rootstock 110R. For this purpose, extracts of grafting tissues were prepared at three different locations (above, below and at the grafting union), and were analyzed in three different stages of the grafting cycle. From all sections analyzed, the graft union tissue is the one to discriminate better the two combinations. Gallic acid, catechin and sinapic acid were found in higher amount at graft union in the less compatible combination later in graft development. Furthermore, the chlorogenic acid had a higher content in the more compatible combination at the early stage when compared to the less compatible graft.