Agronomic evaluation of eight 41 B × 110 Richter grapevine Genotypes as Rootstock Candidates for Mediterranean Viticulture

Choosing the most appropriate rootstock(s)is a key decision for the profitability of vineyards;therefore,there must be a sufficient range of rootstocks in the market adapted to different environmental conditions and production objectives.However,rootstock-breeding programs have been scarce in recent decades,and most of the rootstocks used today were bred a century ago,when the needs of the sector were very different from today.In this work,we aimed to evaluate new rootstock candidates before their introduction in the market.An agronomic evaluation was conducted on eight novel rootstock genotypes obtained from the first generation of the cross-pollination of 41 B Millardet et de Grasset(41 B)and 110 Richter(110 R)grafted with'Syrah'and'Tempranillo'and planted in a typical vineyard of the Ebro Valley in Spain.During the four consecutive growing seasons(2016-2019),growth,yield and berry composition parameters at harvest were collected.A linear mixed-effects model was constructed,considering year and block as random effects.Multiple factor analysis and hierarchical clustering on principal components were performed to establish clusters of genotypes with similar behaviour.The rootstock candidates showed a very wide per-formance range compared to their parents.The trial allowed us to identify two very promising candidates(RG8 and RG10),whose registration as commercial rootstocks is already in progress.