Assessment of the bioherbicidal potential of Thymus sp. pl. essential oils in weed control

The bioherbicidal potential of four essential oils (EOs) from Mediterranean species of Thymus sp. pl.: Thymus algeriensis Boiss. et Reut., T. ciliatus Desf. subspecies coloratus (Boiss. et Reut.) Batt., T. vulgaris L., ecotype Fasano and T. vulgaris L. var. Varico was investigated to identify new sources of biomolecules. In vivo assays were carried out to assess the effect of the EOs on pre and post-emergence of two weed species: Lolium perenne L. and Amaranthus retroflexus L. Four concentrations of EO emulsions (5, 7.5, 10 and 20 µL/mL) were applied. All essential oils (EOs) exhibited the strongest herbicidal activity at the highest tested concentration (20 µL/mL), completely inhibiting seed germination (100 %) in the Vithal control, whereas lower concentrations were less effective. On the contrary, for post-emergence experiments and compared to the positive control, L. perenne showed resistance to the EOs while A. retroflexus was highly sensitive, arguing a selectivity of the EOs. Additionally, cytological analysis were performed on the model plant Arabidopsis thaliana (L.) Heynh, for a better understanding of the structural modifications induced by the EOs. The root system of EO-treated A. thaliana seedlings was highly damaged. • Possible herbicidal activity of Thymus sp. pl. EOs was investigated. • Thymus sp. pl. EOs exhibited a significant herbicidal potential. • Thymus sp. pl. EOs effectiveness was selective on seedlings growth. • Thymus sp. pl. EOs induced morphological and structural damages on A. thaliana roots. • Thyme EOs are a promising agents for sustainable weed control.