Pyramiding of multiple resistances to disease and marker-assisted selection

The durability of resistance against diseases is one of the main aims of genetic improvement. Regarding apples, some scab-resistant cultivars carrying the resistance gene Rvi6 are commercially available and the fruit quality of the last advanced Rvi6 selections is at least comparable to the well-known cultivars. Nevertheless, their commercial interest is still limited. One of the main limits that prevent their further diffusion could be the Rvi6 resistance breakdown that has been already reported in many European countries; however, to date, this resistance is still effective in Italy. In order to pursue a durable resistance, the pyramiding of different scab resistances in the same genotypes has been proposed and this approach was pursued in most of the breeding programs worldwide. To this extent, the development of new apple multiresistant cultivars with advanced selection procedures was started in the framework of the Italian AGER Project. From 2011 to 2013, ten cross combinations have been made among Rvi6 resistant cultivars and other monogenic resistances selections carrying different resistance genes, i.e., Rvi5, Rvi2, Rvi4, and Rvi13. Parents have been chosen according to their previously investigated aptitude in transmitting excellent quality traits and good agronomic performances. A total of 5.722 seedlings have been produced, and the MAS for the presence of traits: Rvi6 + Rvi5; Rvi6 + Rvi13; Rvi6 + Rvi2 and Rvi4 have been started. The progeny plants selected by marker-assisted selection are going to be grafted for the additional selection steps for fruit quality traits and agronomic performance.