Potential Use of Essential oils from Four Tunisian Species of Lamiaceae: Biological Alternative for Fungal and Weed Control

The chemical composition of the essential oils (EOs) of four Lamiaceae (Thymus capitatus Hoff. et Link., Rosmarinus officinalis L., Origanum vulgare L. and Mentha pulegium L.) growing wild in Tunisia was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Obtained results showed significant variations among the different species. The major constituents identified for each species were respectively carvacrol (69%) and δ-terpinene (17%) for T. capitatus, 1,8-cineole (41%) and α-pinene (24%) for R. officinalis, menthol (39%) and 1.8-cineole (17%) for M. pulegium, thymol (30%), p-cymene (30%) and δterpinene (27%) for O. vulgare. EO herbicidal effects were evaluated against three invasive weed species in most cultivated crops: Sinapis arvensis L., Phalaris paradoxa L. and Lolium rigidum Gaud. The study of herbicidal activity was carried out on seed germination and seedling vigor and growth. All tested EOs significantly inhibited the germination and growth of weeds in a dose dependent manner and their herbicidal activity could be attributed mainly to their high content in oxygenated monoterpenes. The antifungal ability of EOs was assessed by using disc agar diffusion against ten plant pathogenic fungi affecting crops and stored foods. The EOs displayed strong inhibitory effect on all tested fungi. Our results on EOs chemical composition and biological activities showed properties that could be valorized in managing biocontrol of weeds and plant fungi.