Genetic diversity of Pyrus pyraster (L.) Burgsd. and P. spinosa Forssk.: evidence of introgression from cultivated into wild pear populations

Southern Europe is home to two naturally occurring pear species: the European wild pear (Pyrus pyraster (L.) Burgsd.) and the almond-leaved pear (P. spinosa Forssk.). In addition to these two species, the cultivated pear (P. communis L.) is also grown throughout Europe. Since the cultivated pear is one of the most widespread fruits in Europe, gene flow between the cultivated species and their wild relatives is to be expected. The aim of this study was to determine the genetic diversity of natural populations and whether gene flow from the cultivated pear can alter the genetic composition of wild pear populations. We collected samples from 21 populations of P. pyraster and 22 populations of P. spinosa as well as 24 cultivars of P. communis. DNA fingerprinting based on nine microsatellite markers (SSR) was used to analyze the genetic diversity and structure of the wild pear populations and to assess the relationship between wild and cultivated pears. In general, we found a higher genetic diversity of P. pyraster compared to P. spinosa. In three Mediterranean P. pyraster populations, significant cultivated-to-wild gene flow was observed, whereas in P. spinosa it was rare and only observed in a few individuals. Furthermore, in regions where the ecological niches of the two wild pear species overlap, hybrids between them were also found. This study provides valuable insights into the genetic variability of these species and can significantly advance their use in sustainable forest management, conservation, and breeding programs.