Genetische karakterisatie van de 17de-eeuwse lindedreef bij de abdij van Tongerlo (Westerlo)

The avenue of common lime (Tilia °— europaea) from the 17th century at the Tongerlo Abbey (Westerlo) is one of the oldest plantings of common lime in Flanders (Northern Belgium). Currently, owners and park managers lack specific knowledge about the plant material required to ensure genetically authentic preservation of this historic avenue. The trees were genotyped with DNA markers (AFLPs). As such, information about the nature of the plant material (clonal versus non‐clonal) and mode of propagation was obtained. This revealed that the majority of the oldest trees (18 out of the 20) consisted of a single clone. It was also confirmed that vegetative propagation of the oldest trees occurred through layering or cuttings since the genotypic composition of the leaves and of epicormic shoots at the base of the trunk of a subsample of trees were identical. Other Belgian and Dutch lime trees planted in the 17th and 18th century (e.g. Westerlo, Tilburg, Sambeek and Nemelaer) turned out to be ‘clone mates’ of the old lime trees of Tongerlo. We also tested whether genetic material from the historic lime avenue differs from recent commercial plant stocks and from common limes found in botanical gardens. Genetic diversity within commercial stocks was extremely limited and consisted mainly of only one clonal group: T. °— europaea ‘Pallida’ (commercially also known as Kaiser Linden or King’s Lime). No clear genetic differences could be found between the varieties morphologically classified as T. °— europaea ‘Pallida’ and T. °— europaea ‘Zwarte linde’. The oldest trees of the common lime avenue at Tongerlo Abbey clearly differed from recent commercial plant material, although several other lime trees classified as ‘trees of cultural heritage’ belong to the clonal group ‘Pallida’. This suggests that the genetic diversity of the historic trees as well as the diversity of recent plantings of common lime is extremely limited. From a cultural heritage perspective, we suggest to clonally propagate the oldest trees from the Tongerlo Abbey avenue. These saplings can then be used to fill potential gaps in the avenue.