Advances in Apple Breeding and Genetic Control of the Main Agronomic Resistance and Fruit Quality Traits

The new apple consumer trend follows a wide market range from sweet and aromatic types, to sour and firm, crisp and juicy flesh; with very varied skin colors. The main objectives being pursued by breeding programs include fruit quality, resistance to biotic stresses, environmental adaptability and enhanced bearing (growth habit, fruiting limbs, yield efficiency and stability, and so forth). Studies of parental lines via various approaches allow identification of the sources of qualitative and quantitative traits. Polymorphic DNA markers, like SSRs and SNPs associated to gene sequences are now largely available, as are expressed sequence tags (EST) libraries to the whole genome sequences. Several institutions, including FEM (San Michele all'Adige, Italy), which carried out the apple genome sequence, have made large contributions to these advances. The authors analyze the advances in knowledge on the genetic control and the availability of linked markers which has allowed the introduction of MAS methodology (Marker Assisted Selection) for several tree and fruit quality traits. Nevertheless the dramatic recent molecular technologies advancements also need an improvement of phenotypic research, which appears now to be the bottle neck for future molecular genetic studies.