Bioherbicidal potential of Aqueous Extracts and Essential Oils of Rosmarinus Officinalis L. and Thymus Vulgaris L.

Abstract

Purpose Weed control is a technique attempts to stop or reduce growth of noxious weeds, with the aim of reducing their competition with desired crop and in natural settings preventing nonnative species competing with native ones. The essential oils and aqueous extracts from Rosmarinus officinalis (Rosemary) and Thymus vulgaris (Thyme), have been investigated as bioherbicides to suppress two weeds; Chenopodium albumand Echinochloa crus-galli associated with two important economic crops; Triticum aestivum (wheat) and Oryza sativa (rice) respectively. Methods Petri-dish experiment was performed and 10, 20, 50, and 100% aqueous solution and doses of 0, 2, 4, 8 and 16 µL of essential oil per petri dishes were applied. Number of germinated seeds in each Petri dish was counted daily. After 15 days, germination percentage, germination velocity, speed of germination, germination energy, germination index, mean germination time as well as seedling shoot length, root length, shoot root ratio and seedling vigour index were recorded. The chemical profile for both essential oils were identified with GC-MS analysis. Results Eucalyptol (1,8-cineole), α-pinene and camphor were identified as the dominant constituents of the rosemary essential oil. The detected major components of thyme essential oil were Thymol, o-Cymene, caryophyllene and gamma-terpinene. The results showed that thyme essential oils had the most negative effect by inhibiting the germination of weeds. Both rosemary and thyme essential oil caused a generally reducing effect on growth parameters of weeds. Conclusions Essential oil of rosemary and thyme had allelopathic potential and should be assessed as allelopathic agents to be used for weed control.