Introduction: Allelopathy is the result of biologically active molecular production by plants in growing or their residues, which may affect the growth and development of the same species or other species. In the field of allelopathy, there are different bioassay methods, most of which are related to changes in germination rate and seedling growth due to plant potential. Therefore, the purpose of the present study was to evaluate the hetrotoxicity potential of Thymus kotschyanus hydro-methanolic extract on germination and seedling growth of Avena ludoviciana and Triticum aestivum.

Materials and methods: To study the various concentrations effect of hydro-methanolic extract of Thymus kotschyanus on germination traits and seedling growth of Avena ludoviciana and Triticum aestivum- Morvarid cultivar, two experiments were conducted based on completely randomized design in three replications separately. To extract Thymus kotschyanus, 10% suspension containing water and methanol in the ratio of 80: 20 was prepared respectively. Then from concentrated extracte, five concentrations of 0 (control), 25, 75, and 100% with the help of distilled water were prepared. 10 ml of each concentration was applied to 25 disinfected seeds of Avena ludoviciana and Triticum aestivum separately. Measured traits included germination percentage and rate, radical and shoot length, and radical and shoot dry weight.  

Results: Results showed that measured traits of Avena ludovicans weed were decreased using various concentrations of Thymus kotschyanus hydro-methanolic extract. So, no germination was observed in the higher concentrations of 25%. In the case of wheat, germination and seedling growth also were decreased with an increase in concentrations of Thymus kotschyanus hydro-methanolic extract. In general, thyme hydro-methanolic extract had different decrease effects on germination traits and seedlings of Avena ludoviciana and wheat. This might be due to differences in the quantity and quality of allelochemicals and their increased toxicity to the physiological reactions of plants.

Conclusion: Results showed that Thymus kotschyanus hydro-methanolic extract has a different allelopathic potential on traits of germination and seedling growth of Avena ludoviciana and Triticum aestivum.  Therefore, according to the proof of the detrimental effect of Thymus kotschyanus extract, it can be a candidate for the production of herbicides of natural origin.