Genetic Characterization of the Norwegian Apple Collection

Commercial fruit production in Norway is located at around latitude 60° north, demanding careful choice of adapted cultivars. The most comprehensive collection of apple genetic resources in Norway is being kept in the Norwegian Apple Collection (NAC) at Njøs Fruit and Berry Centre (NJØS). The collection contains around 350 accessions and was recently genotyped with a single nucleotide polymorphism (SNP) array. Curated SNP data were used for structure assessment, diversity analysis, pedigree confirmation, and core collection development. In the subsequent SNP analysis, we identified several duplicates and parent–offspring relationships. The collection was equally diverse across the geographic regions represented. Different methods for analyzing population structure were applied. K-means clustering and a Bayesian modeling approach with prior assumptions of the data revealed five subpopulations associated with geographic breeding centers. The collection has a distinct genetic structure and low relatedness among the accessions; hence, two 100 accession core collections were created. These new core collections will allow breeders and researchers to use the NAC efficiently. The results from this study suggest that several of the accessions in the Norwegian Apple Collection could be of high importance for breeding programs.