Physiological Interaction between Rootstock-Scion: Effects on Xylem Vessels in Cabernet Sauvignon and Merlot Grapevines

Abstract

The interaction between rootstock and scion can influence the vegetative and productive balance of grapevines. Vascular connections and patterns may be related to the observed phenotype of certain rootstock-scion combinations. However, little is known about the physiology of the rootstock-scion interaction and the related anatomical variables. The aim of this study was to evaluate the effect of the rootstock-scion interaction on the vegetative growth of Vitis vinifera L., with a focus on the vascular system. We investigated the rootstock genotypes 1103 Paulsen (Vitis berlandieri Planch. × Vitis rupestris Scheele), 101-14 Mgt (Vitis riparia Michx. × V. rupestris), and SO4 (V. berlandieri × V. riparia) grafted on the Cabernet Sauvignon and Merlot grapevine varieties. We evaluated vegetative growth variables and performed an image analysis of the vascular system by quantifying the xylem and vessels (diameter, total number, density, and frequency) in different portions (apical, median, and basal) of the scion stem. The rootstock-scion interaction caused differences in vegetative growth and was associated with differences in the vascular system. The vegetative growth of the Cabernet Sauvignon on 1103 Paulsen and Merlot on SO4 combinations was greater than the growths of either variety grafted on 101-14 Mgt. The more vigorous rootstock-scion combinations had vessels with greater mean diameters, xylem areas, and proportion of vessels with diameters greater than 50 μm. Vines grafted on 101-14 Mgt had a greater proportion of vessels with diameters less than 40 μm. The vessel features were altered from the apex to base sections (stem morphology) in all combinations. The physiological interaction between rootstock-scion modified the vascular system in grapevines by altering the xylem vessel.