Grafting Vitis vinifera on to Phylloxera resistant rootstocks is necessary in most wine growing regions of the world and therefore viticulture relies heavily upon successful graft union formation between the scion and the rootstock. The process of graft union formation begins with formation of a necrotic layer, followed by adhesion of the two grafted partners, callus cell proliferation and the establishment of a functional vascular system. Initially two-dimensional (2D) classical microscopy studies were performed to describe graft union formation. However, the establishment of graft union takes place in 3D and the lack of data in the third dimension makes it difficult to understand the process. In order to overcome this lack of information, 3D imaging techniques have been used, but with limited resolution. Here we will present methods to characterize the 3D morphological developments at the graft interface of grapevine using X-ray microtomography (micro-CT). This technique provides information on tissue architecture in relation with X-ray tissue absorbance and was used to visualize the 3D organization of callus and vascular tissues. In addition, we used iohexol, a contrast agent, to visualize functional xylem vessels connecting the scion and the rootstock. Images were compared before and 24 h after feeding iohexol to cut roots from where it moved to the shoot and labelled xylem vessels at the graft interface. These techniques were used to characterize xylem vessels connected between the scion and rootstock of grafts produced with different grafting techniques. © 2024 International Society for Horticultural Science. All rights reserved.< Leer menos