Caracterización agronómica y ampelográfica de la serie RG de portainjertos de vid y estudio de las implicaciones de la calidad de la conexión del injerto sobre el comportamiento de la planta
Authors:   , Marín Ederra Diana , Torres Molina Nazareth 
Published: October 2022

The arrival of phylloxera in Europe around 1868 was one of the greatest agricultural crises in history, and the use of tolerant American rootstocks was the only successful solution to halt its advance. The enormous quantity of plants required for rebuilding the European vineyard led to the development of the nursery sector, which has been supplying vine growers with planting material since then. This PhD thesis addresses two challenges that currently are major concerns for the nursery sector: (i) optimising the choice of rootstock and (ii) improving the physiological quality of the grafted plants produced. Specifically, the first challenge has been approached from two perspectives: the need to increase knowledge of the influence of conventional rootstocks on different varieties under different conditions and, secondly, the development of new rootstocks suitable for Mediterranean conditions. The second challenge has been addressed through the study of the implications of scion and cane alignment during grafting on the success rate in the nursery and on the subsequent behaviour of the plant. In relation to the use of conventional rootstocks, an agronomic monitoring of Syrah and Tempranillo varieties grafted onto 12 conventional rootstocks was carried out during 4 years (2015- 2018) in a typical vineyard of the Ebro Valley established by the Vitis Navarra nursery in Miranda de Arga (Navarra). Measurements of growth, yield and grape composition at harvest were carried out, showing a clear effect of the rootstock on the agronomic behaviour of both varieties, with a relevant impact on growth and yield parameters, consequently affecting ripening. Regarding the development of new rootstocks, the agronomic characterisation of 8 new hybrids of the RG series, obtained from the first generation of a cross between rootstocks 41 B MGt and 110 R as a result of a hybridisation programme carried out by Vitis Navarra nursery, was conducted in a plot with Syrah and Tempranillo grafted onto these hybrids. During four years (2016-2019), measurements of growth, production and grape composition were performed, demonstrating that a hybridisation programme based on a simple cross allows the obtention of new hybrids of agronomic and commercial interest. The evaluation carried out in this thesis, together with other trials performed by the nursery and other entities, has identified several very promising candidates and has promoted the registration of some of them, increasing the variability available to the sector. Related to the second challenge, this doctoral thesis has addressed the study of the implications of the alignment of the scion and the cane on (i) the behaviour of the plants in the nursery and in (ii) the first years in the vineyard and (iii) their water and hydraulic behaviour in a trial with plants grown in pots. The results obtained have underlined the importance of implementing good practices at the time of grafting that allow good alignment between individuals. Thus, plants with complete alignment significantly increased the success rate in the nursery and showed superior growth, both in the nursery and in their first year of establishment in commercial vineyards and in pots, although these differences faded over the years. Plants with complete alignment between scion and cane also showed higher levels of leaf gas exchange in the pot trial, but these differences were not reflected in the hydraulic conductivity measurements through the graft junction. The results obtained throughout this doctoral thesis have allowed to deepen the knowledge of the hybrids of the new RG series prior to their possible introduction in the market and to highlight the importance of a good alignment between the scion and the cane at the time of grafting.