Genetic integrity is still maintained in natural populations of the indigenous wild apple speciesMalus sylvestris(Mill.) in Saxony as demonstrated with nuclear SSR and chloroplast DNA markers

Malus sylvestris(Mill.) is the only indigenous wild apple species in Central Europe. Agriculture, forestry, and urbanization increasingly endangerMalus sylvestrisnatural habitats. In addition, the risks of cross-hybridization associated with increase in the cultivation of the domesticated appleMalus x domestica(Borkh.) threaten the genetic integrity ofM. sylvestris. The present study investigated the number of hybrids, genetic diversity, and genetic structure of 292 putativeM. sylvestristhat originate from five different naturalM. sylvestrispopulations in Saxony, Germany. All samples were genetically analyzed using nine nuclear microsatellite markers (ncSSR) and four maternally inherited chloroplast markers (cpDNA) along with 56 apple cultivars commonly cultivated in Saxony. Eighty-seven percent of the wild apple accessions were identified as pureM. sylvestris. The cpDNA analysis showed six private haplotypes forM. sylvestris,whereas three haplotypes were present inM. sylvestrisandM. x domestica. The analysis of molecular variance (AMOVA) resulted in a moderate (ncSSR) and great (cpDNA) variation among pureM. sylvestrisandM. x domesticaindividuals indicating a low gene flow between both species. The genetic diversity within the pureM. sylvestrispopulations was high with a weak genetic structure between theM. sylvestrispopulations indicating an unrestricted genetic exchange between theseM. sylvestrispopulations. The clear distinguishing ofM. sylvestrisandM. xdomesticaconfirms our expectation of the existence of pureM. sylvestrisaccessions in this area and supports the argument for the implementation of preservation measures to protect theM. sylvestrispopulations in Saxony.