Comparative evaluation of seed germination of five Mediterranean sage species (Salvia sp.) native to Greece

Salvia sp. (Lamiaceae) comprises about 900 species worldwide, many of which are used as ornamental or medicinal plants. In the present study, the effect of seed pretreatment by surface scarification (mechanical or chemical) on germination of five Mediterranean sage species, S. fruticosa, S. officinalis, S. pomifera ssp. pomifera, S. ringens, and S. tomentosa was examined. Seeds were harvested from native populations in August 2018 and stored in the dark, at room temperature, for 5 months. The seeds were surface sterilized with commercial bleach solution (20% for 15 min) and placed for germination in vitro, in Petri dishes, with a solid (8 g L^‑1 agar) half-strength MS medium containing 20 g L^‑1 sucrose, at 15°C and 16-h photoperiod, either without pretreatment (control) or after scarification with sandpaper (suitable for metal surfaces) for 1 min or after dipping in dense H₂SO₄ for 15 min. In S. fruticosa higher seed germination percentages were observed after mechanical or chemical scarification compared to the control, whereas in S. officinalis dipping in H₂SO₄ was the most effective pretreatment. In the other three species, very low germination percentages (<28%) were generally observed irrespectively of pretreatment. In all species, seeds immersed in dense H₂SO₄ reached faster T₅₀ than those that received mechanical scarification or no pretreatment. In conclusion, pretreatment by mechanical or chemical scarification had a favourable effect on seed germination of S. fruticosa and S. officinalis, whereas in S. pomifera ssp. pomifera, S. tomentosa and S. ringens further investigation is required.