Origanum dictamnus L. (Lamiaceae), a local endemic plant of Crete (Greece), creates polysaccharide-containing subcuticular compartments presenting biological activity against phytopathogenic fungi, and, among others, significantly affecting the fungal cell wall polysaccharides. This field study introduces a fertilization scheme for O. dictamnus, which was developed and refined to optimize yield as well as critical herbal quality aspects. Five fertilization schemes were investigated, based on a polysaccharide-based Integrated Nutrient Management (INM), a mixture of chemical fertilizers and two biostimulants (not algae) via foliar and soil application. Plant growth, together with leaf chlorophyll fluorescence and colour (SPAD meter, DA meter, Chroma Meter) were determined. The leaf content of chlorophyll, three critical antioxidant compounds (carotenoids, flavonoids, phenols) and minerals were also assessed. Considering all three antioxidants together, the enhanced efficiency, non-toxic, water-soluble, polysaccharide-based INM by foliar application was the most stimulatory scheme, playing an important role in plant growth and development. The present field study provides for the first time baseline fertilization data improving key herbal quality features in O. dictamnus and unravels the attainment of high antioxidant properties. The latter may be exploited in favor of its further utilization as raw material for tea preparation, medicinal purposes, natural food flavoring and/or food preservative.

Herein, we applied DNA Barcoding for the genetic characterization of Sideritis syriaca subsp. syriaca (Lamiaceae; threatened local Cretan endemic plant), using seven molecular markers of cpDNA. Five fertilization schemes were evaluated comparatively in a pilot cultivation in Crete. Chemical fertilizers (ChF), integrated nutrient management fertilizers (INM) and two biostimulants were utilized (foliar and soil application). Plant growth, leaf chlorophyll fluorescence and colour were assessed, and leaf content of chlorophyll, key antioxidants (carotenoids, flavonoids, phenols), and minerals were evaluat-ed. Fertilization regime did not affect leaf colour but induced distinct differences in leaf shape altering quality characteristics. INM-foliar and ChF-soil application promoted yield, without affecting tissue water content or biomass partitioning to inflorescences. ChF-foliar application was the most stimulato-ry treatment for enhanced antioxidant compound content, while INM-biostimulant was the least effec-tive one. In conclusion, adverse fertilization options appear as optimal when considering yield or anti-oxidant compound content. New DNA sequence datasets for the plastid regions of petB/petD, rpoC1, psbK-psbI and atpF/atpH have been deposited in the GenBank for S. syriaca subsp. syriaca while the mo-lecular markers rbcL, trnL/trnF, psbA/trnH were compared to those of another 15 Sideritis species re-trieved from the GenBank, constructing a phylogenetic tree to show their genetic relatedness.