Genetic diversity in Swedish and Finnish heirloom apple cultivars revealed with SSR markers

- SSR markers were used to estimate genetic diversity and structure in a subset of Swedish and Finnish heirloom apple cultivars.
- Differentiation was observed. Also Bayesian model-based clustering revealed the existence of defined groups.
- Genetic distinctness of Finnish apple cultivars from Swedish and European ones was observes.

A set of 85 heirloom apple cultivars aimed for long-term preservation in two germplasm collections in Sweden and Finland was evaluated with 8 SSR primer pairs to evaluate genetic diversity and genetic relatedness. An additional set of 16 European cultivars was included for comparison. The eight SSR primer pairs amplified 9 loci and 105 alleles. Genetic analyses performed by MDS indicated some differentiation between Swedish and Finnish cultivars, with European cultivars intermixed with the Swedish. The existence of three groups was, however, indicated by a Bayesian model-based clustering. One of the groups was clearly dominated by Swedish cultivars and another by Finnish. The third group included almost equal proportions of representatives from all three areas. The obtained results confirmed the genetic distinctness of Finnish apple cultivars, which can be explained by climate adaptation and admixture with a Russian gene pool.