Preliminary genetic approach based on both cytogenetic and molecular characterisations of nine oak species

The Quercus genus includes several species and presents a huge genetic variability. In the last decades, studies regarding genetic diversity and molecular characterisation in Quercus emerged. In this work, we intend to characterise nine Quercus species at cytogenetic and molecular levels. Cytogenetically, we aim to evaluate the ribosomal RNA genes expression, and to determine the physical mapping of the rDNA loci using both salt-nylon silver staining and double-target fluorescent in situ hybridisation (FISH) techniques. Molecularly, our goals were to characterise and determine the genetic variability using Inter-Simple Sequence Repeats (ISSRs). All individuals were euploid (2n = 2x = 24), and presented a maximum number of four Ag-NORs and four nucleoli per mitotic cell. FISH confirmed the Ag-NORs localisation, and evidenced that all 45S rDNA loci are being actively expressed. Two additional 5S rDNA loci were also detected. Cytogenetic analyses did not allow us to distinguish the oak species. Inversely, ISSR data revealed that the oak species under study presented genetic variability, and showed unique bands which could be putative species-diagnostic markers. The UPGMA phenogram reflected the reliability of the ISSR markers since most individuals belonging to the same species were clustered together.