Genetic and Pomological Determination of the Trueness-to-Type of Sweet Cherry Cultivars in the German National Fruit Genebank

Genebank collections preserve many old cultivars with ancient breeding history. However,
often, cultivars with synonymous or incorrect names are maintained in multiple collections.
Therefore, pomological and genetic characterization is an essential prerequisite for confirming trueness-
to-type of cultivars in gene bank collections. In our study, 1442 single sweet cherry (Prunus
avium L.) trees of the German Fruit Genebank were evaluated according to their trueness-to-type.
For this purpose, pomological analysis was performed, in which the accessions were assigned totheir
historical cultivar names. The pomological identifications were based on several historical reference
sources, such as fruit references from historical cherry cultivar and fruit-stone collections, as
well as historical pomological literature sources. In addition, the cherry trees were genetically analyzed
for cultivar identity using 16 SSR markers. Based on pomological characterization and genetic
analysis for the majority of the trees (86%), cultivar authenticity could be confirmed. Most markers
were highly discriminating and powerful for cultivar identification. The cherry collection showed a
high degree of genetic diversity, with an expected heterozygosity He = 0.67. Generally, high genetic
admixture between cultivars of different geographic origin and year of origin was obtained after
STRUCTURE analysis, demonstrating the extensive exchange of genetic information between
cherry cultivars in the collection over time. However, the phylogenetic tree calculated by DARwin
reflected the geographic origin of selected cherry cultivars. After parentage analysis with CERVUS,
paternity could not be confirmed for three cultivars, indicating the necessity of further pedigree
analysis for these cultivars. The results of our study underlined the general importance of evaluating
the authenticity of cultivars in genebank collections based on genetic and pomological characterization.