Essential Oil Compositions and Natural Herbicide Activity of Four Denaei Thyme (Thymus daenensis Celak.) Ecotypes

Abstract

Denaei Thyme (Thymus daenensis Celak.) is a perennial plant from Lamiaceae family. The plant's leaves possess biological attributes that provide it with the potential to be used for medicinal purposes and newly for suppressing the growth of herbaceous plants. In this study essential oil (EO) compositions and phytotoxic effects of four T. deanensis ecotypes (ECTPs) of T. deanensis were evaluated on Amaranthus retroflexus, Avena fatua, Datura stramonium and Lepidium sativum germination and related growth traits.For this purpose, thyme plants were collected from different ecological locations of Fars Province, Iran to identify EOs content and compositions and also their phytotoxic activity. Gas chromatography (GC) and GC-Mass spectrometry (GC-MS) analysis of the EOs showed that thymol (20 - 60.5 %) and carvacrol (20.1 - 63.4 %) were the two major oil components found in the studied ECTPs. For evaluating phytotoxic activity, the concentrations, 0, 200, 400, 600, 800 and 1000 µl l-1 of the EOs were tested in vitro against seeds and their effect on germination percentage and rate, root and shoot length, fresh and dry weight of seedlings were determined. In general, higher EO concentration resulted in lower germination percentage and/or rate in all studied species. The overall results of germination test represent a reduction in germination percentage of most species at concentration of 200 µl l-1. The results reported herein suggest that herbicidal properties of the four ECTPs could be due to their EO concentrations and have potential as natural herbicides.