Characterization of a genepool of old broad leaf Rhododendron hybrids by means of STMS markers

During the 19th century many broad-leafed woody evergreen Rhododendron cultivars (subgenus Rhododendron) were introduced in Italy as ornamental garden plants. The most comprehensive collection is located in the Special Natural Reserve of Burcina Park “F. Piacenza” (Biella-Piedmont), that represents a rich reservoir of germplasm for its favourable climatic and pedologic conditions. The aim of the present work was to deepen the knowledge about these cultivars that represent an important genetic patrimony, since a number of them are deceased world wide. In order to investigate the genetic diversity of 10 rhododendron hybrids and 4 supposed related species (R. arboreum, R. catawbiensis, R. ponticum and R. caucasicum), 17 variables referring to flower and leaf morphology and four polymorphic sequence-tagged microsatellites sites (STMSs) were evaluated. Similarities among accessions were assessed performing a Principal Coordinate Analysis (PcoA) based on Gower coefficient. In the scatter plot the hybrids clustered in groups that were consistent with their supposed pedigrees and further bibliographic information. Based on these results, some hypotheses about the origins of the cultivars with unknown parentage included in the analysis could be drawn. In conclusion, the evaluated morphological and molecular markers appeared to be a useful tool for solving identification and classification problems of the old broad leaf rhododendrons hybrids and for clarifying their origins.