The diversity in plant genetic resources is a prerequisite for genetic improvement of cultivated
crop species. Lack of in-depth characterization and evaluation of gene bank accessions is a
major obstacle for their potential utilization. The Danish apple (Malus domestica L.) gene
bank collection represents an ensemble of cultivars that have never previously been genetically
accessed. The aim of this thesis is to study the genetic structure, affiliation and overall diversity
which should facilitate future conservation management strategies. It may also contribute
with new knowledge for better understanding of the link between phenotypes and the
underlying gene-tic background which is crucial in plant breeding. We found a considerable
genetic diversity in the collection and no genetic structure. We exposed a high number of accessions
in admix and revealed several putative cultivar parentages, never previously reported.
Unique fingerprints were obtained for all accessions except for distinctive subclonal sports
and synonym accessions. The cultivar ensemble was shown to hold 22% triploid accessions.
We developed a new protocol for genotyping S-RNase alleles in apple and revealed 25 different
alleles, including several rare alleles. Using historical gene bank records, including aroma
volatile analysis, sugar and acid data and other fruit- and tree character records, we established
genotype-phenotype relationships, performing a genome-wide association study. A
number of SNP markers are presented that can be used directly for marker-assisted selection.
In addition, we suggest a number of candidate genes involved in the control of several important
fruit quality traits. Future studies and breeding attempts can therefore benefit from the
results, including genetic fingerprints and pedigree reconstruction. In addition, several of the
SNP markers presented can be used directly in selection for specific traits in breeding lines.
However, further characterization and evaluation of additional important horticultural traits
are still needed for upmost utilization of the apple gene bank collection.