Genetic diversity within and among wild strawberry (Fragaria vesca) populations in the Nordic countries

Abstract Crop wild relatives (CWR) are wild plant taxa that are closely related to crops and other cultivated species. The importance of conserving CWR genetic diversity as a valuable source of variation for plant breeding has been regularly brought forward, and knowledge about the distribution of genetic diversity within and among natural populations can aid in efficient conservation and increased availability of CWR genetic resources. Within the Nordic countries (Iceland, Norway, Denmark, Sweden and Finland), the European wild strawberry, Fragaria vesca L., has been recognized as a CWR of priority. However, information about the distribution of its within- and among-population genetic diversity in the Nordic countries is limited. In total, 180 individuals from twelve populations covering the majority of the Nordic range of F. vesca were genotyped with 14 microsatellite markers. Overall, populations had high inbreeding coefficient F IS values, although a large variation was observed across the region. In agreement with expectations, populations from higher latitudes tended to have less genetic diversity and a higher presence of genetically identical individuals, possibly the result of clonal propagation. The analysis of molecular variance (AMOVA) showed that genetic diversity was primarily distributed among populations within countries, supporting a regional conservation approach. Analysis of the geographic distribution of the genetic diversity with STRUCTURE and principal component analyses and calculation of pairwise F ST values revealed that the studied individuals formed clusters which partially, but not completely, corresponded to the geographical origin of the populations. The inclusion of multiple individuals per populations allowed geographic clustering to be detected on a finer scale than previously described. Ex situ conservation of F. vesca is recommended mainly to improve availability of these genetic resources for research and breeding and based on the within- and among-population distribution of genetic diversity, prioritizations are suggested.