Rootstock effect in response to top grafting in Ribeira Sacra (Northwest–Spain)

Abstract

Mountain viticulture presents clear challenges for optimal soil preparation and tillage, a work possible only at the time of slope terrace construction. These conditions affect replanting when initial clone or varietal selection proves unsuited to the site. Viticultural revival in the area has led to new plantings with selected plant material, but sometimes the response of the limited number of vinifera clones used was below expectations. Top-grafting by chip budding, when controlled healthy scions are provided, has the advantage of a rapid achievement of full production; it is also useful for a fine tuning of plant material to plot variations. Changes of variety or clone have been tried by several agricultural service companies with uneven results. After a check of performance of different grafting methods, the effect of the rootstock was tested. The study was carried out in an experimental plot in the the Ribeira Sacra planted in 2004 with seven rootstocks which were low level top-worked by cleft grafting in 2006. During 2013 and 2014, every rootstock was top-grafted by chip budding with buds of certified Godello cv. by the same experienced professional grafting team. Trunk cross section at 15 cm, shoot length and diameter at the base of each plant were taken at the end of the growing season. Rootstock cross section gives an estimate of vigor which was significantly higher in Gravesac and 1103P. Successful engraftment was directly related to temperatures after grafting. There were no significant differences in growth between grafts done in 2013 due to high variability. In 2014, 1103P, 420A and SO4 showed the most vigorous growth. The correlation between rootstock caliber and pruning weight in grafts performed in 2013 was not significant except for 420A. In 2014 grafts the correlation was always positive and significant for most rootstocks.