Genetic differentiation among populations from Italy and Bosnia-Herzegovina of common ash (Fraxinus excelsior L.) and identification of regions of provenances

Common ash (Fraxinux excelsior L.) is a forest tree widespread in most of Europe. In spite of its importance as forest tree species, the population genetics of common ash received relatively little attention and only a few European countries are managing gene conservation programmes. Italian Government has recently issued the act no. 386/2003, that implements the European Council Directive 1999/105/CE, concerning the marketing of forest reproductive material. One of the most important feature of the act is the definition of Region of Provenance, that play a basic role for a rational management of activities linked with forest trees propagation, including afforestation and in situ genetic preservation. The purpose of this study was the evaluation of neutral DNA markers (microsatellites) as a tool to study genetic variability distribution of common ash (Fraxinus excelsior L.) in Italy and Bosnia-Hercegovina, and to group populations according to their genetic similarity. 41 natural ash populations, representing the locations where the species grows in Italy and Bosnia-Hercegovina, were sampled and DNA was extracted from young leaves or winter buds. Six microsatellite primer pairs were used to detect genetic variability. Levels of within and among populations variability were estimated and genetic differentiation was calculated. Additionally, the ecological chracteristics of the collection sites were analysed and homogeneous regions were defined. Lastly, patterns of genetic and ecological variations were compared, allowing us to identify areas that are both ecologically and genetically homogeneous.