Phenotypical description of traditional apple cultivars from Sierra Norte de Madrid (autonomous community of Madrid, Spain)

To assess phenotypical variability, 15 traditional cultivars of apple (Malus domestica), were collected in nine municipalities from Madrid and evaluated and compared with eight commercial cultivars and four wild apple tree (Malus sylvestris) collections using 66 morphological descriptors. The studied trees were first established in a Fruit Germplasm Bank and maintained by the Madrid Institute for Research and Rural Development in Food and Agriculture (IMIDRA). Both quantitative and qualitative obtained data were analyzed by principal component analysis (PCA) to detect the main sources of variability in evaluated plant material, allowing the selection of the best descriptors for the cluster analysis (CA). This study provides information about the phenotypic diversity of the endangered traditional cultivars from of the mountains of Madrid, which is a compulsory step for future conservation and genetic breeding programs.