13th Conference on Medicinal and Aromatic Plants of Southeast European Countries (CMAPSEEC 2026)

Background: Many important medicinal and aromatic plants belong to the Lamiaceae family. However, breeding progress has long been hampered by a lack of genetic tools. Currently, the rise of affordable, high-quality sequencing platforms facilitates the development of such resources. Within the project OptiLamia, we aim to establish marker-assisted breeding tools with a focus on terpenoids in Melissa officinalis, Origanum spp., and Thymus vulgaris. In this poster, we present our current work on Melissa officinalis.
Materials and Methods: We analyzed the genetic diversity and population structure of 256 genotypes from international accessions using flow cytometry and genotyping-by-sequencing (GBS). Furthermore, we conducted phenotypic and chemotypic evaluations in a two-year field trial across two locations.
Results: Morphological characterization and flow cytometry revealed a clear division by ploidy and subspecies (officinalis vs. altissima). GBS analysis identified significant genetic differentiation between the subspecies, as confirmed by PCA, STRUCTURE, and hierarchical clustering. Within ssp. officinalis, several clusters of untapped genetic diversity from Armenia, France, Georgia, and Spain were identified. Field data support a strong separation of subspecies for many traits, including terpenoid profiles. Within ssp. officinalis, we detected high diversity in both terpenoid concentration and composition. Preliminary GWAS results indicate that several QTLs for terpenoids are present in the diversity set.
Conclusions: The genetic diversity identified in this study offers promising opportunities for future breeding. These efforts can be effectively accelerated by molecular tools, which will be developed based on our GWAS results.