Inhibitory effect of rosemary essential oil, loaded in liposomes, on seed germination of Acacia saligna, an invasive species in Mediterranean ecosystem

Acacia saligna (Labill.) Wendl. is native of southwestern Australia, but has been planted extensively in many areas of the world, including the Mediterranean region, becoming highly invasive especially in coastal habitats. The aim of this study was to test whether the indigenous Rosmarinus officinalis L essential oil (EO), loaded in liposomes, can inhibit the seed germination of the invasive alien Acacia sangria. Variability in seed germination requirements and responses among populations were evaluated. Germination tests under light, at constant temperatures and three concentrations of rosemary EO were carried out. Among the examined factors, only the EO amount and temperature had a highly significant effect on seed germination. The lowest EO quantity did not show differences compared with the control, while the highest amount inhibited significantly seed germination of all populations at all the tested temperatures. No seed recovered the ability to germinate after the EO treatment with either of the two washing methods. Our results allowed us to identify the minimum amount of rosemary EO capable of inhibiting the seed germination of the invasive Acacia saligna. These results could be useful for the control of this invasive alien species, thus allowing the conservation of indigenous Mediterranean plant species and habitats.