Assessment of genetic diversity within sour cherry clones

Harvested yields of sour cherry (Prunus cerasus) cultivar 'Stevnsbaer' clones grown in Denmark have been highly variable over the years, yet some propagated derived trees selected from within the two widely grown clones of 'Stevnsbaer' clone 'Birgitte' and clone 'Viki' have consistently produced higher yields. A number of these selections were evaluated for yield and genomic differences to investigate variation between and within the 'Birgitte' and 'Viki' clones. Variation in yield was mainly found at the clonal level. The clone 'Viki' was found to be the highest yielding with an average of 20 kg/tree compared to only 7.0 kg/tree from clone 'Birgitte'. The selected trees derived from within clone 'Birgitte' had a significantly higher, average yield over 7 years compared to the original 'Birgitte', indicating that such within-clone selection may be a possible approach for selection of improved breeding material. However, no differences in allele profile were found between or within the clones, calling into question the extent of the available genetic diversity and indicating that the observed variance in yield may have to be explained by other genetic mechanisms, including epigenetic change.