STMSs markers demonstrate genetic differentiation in ornamentals genus: the case of old garden roses and camellias

relatives. Effective conservation and use of plant genetic germplasm depend on the availability of information and on the extent and distribution of genetic diversity in species of interest. Such information allowed to improve conservation management and help users to find material with desirable characteristics. In recent years, numerous molecular techniques have been developed to provide markers and now are by far the most powerful and widely used. Among the several classes of DNA-based markers, the STMSs (Sequence Tagged Microsatellite Sites) are highly polymorphic, multi-allelic, frequently co-dominant, highly reproducible, selective neutrality and random widely distributed in the genome. In order to improve the genetic knowledge in ornamentals and to solve taxonomical issues, STMSs were applied in two among the most economically important plants: garden roses and camellias. Roses have been cultivated as ornamental plants for more than 2000 years. The existence of many species together with the high level of interspecific and inter-sectional hybridisation make confused the genetic relationships within the genus. A phylogenetic analysis on 18 species and 47 cultivars using STMSs markers was carried out to clarify the classification of Old Garden Roses (OGRs) and quantify the discriminating power of the loci. Six microsatellites primer pairs, located on at least 4 different linkage groups, were selected. A total of 82 alleles were detected with an average of 13.7 alleles per locus. The number of allelic phenotypes per locus ranged from 15 to 50 with an average of 34.7. The UPGMA clustering of Jaccard similarities was in good agreement with the botanical classification and with previous phylogenetic approaches based on matK and on cpDNA analyses, confirming the relative position in the dendrogram. Taxonomical problems mainly due to natural inter specific hybridization occur also in the genus Camellia. Many species are economically important plants with ornamental value, such as C. japonica and C. sasanqua. A total of 132 accessions belonging to Camellia spp., including C. sasanqua, C. japonica, C. x vernalis, C. x hiemalis and C. hybrida cultivars were analyzed by 4 STMSs developed in C. japonica. These markers successfully amplified 24 species, demonstrating their cross-transferability. The constructed PCoA (Principal Coordinate Analyses) showed a distribution of all accessions in agreement with their taxonomic classification. The spatial distribution on the scatter plot, allowed to demonstrate that the STMSs were able to describe genetic diversity both in winter and spring camellias. In conclusion, the good STMS cross-species transferability observed in roses and camellias makes these sets of microsatellite loci an appropriate tool for germplasm characterization and management.