Aqueous methanol extracts of rattail fescue (Vulpia myuros) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis and Lolium multiflorum. Increasing the extract concentration increased the inhibition, suggesting that rattail fescue may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of rattail fescue was purified and two main inhibitory substances were isolated and identified by spectral data as (-)-3-hydroxy-b-ionone and (?)-3-oxo-a-ionol. Both substances inhibited root and shoot growth of cress at concentrations greater than 0.3 lM. The concentrations required for 50% growth inhibition on root and shoot growth of cress, lettuce, alfalfa, timothy, D. sanguinalis and L. multiflorum were 2.7-19.7 lM for (-)-3-hydroxyb-ionone, and 2.1-34.5 lM for (?)-3-oxo-a-ionol. The concentration of (-)-3-hydroxy-b-ionone and (?)-3-oxo-a-ionol, respectively, in rattail fescue was 7.8 and 3.7 lg g -1 fresh weight. Considering the endogenous level and the inhibitory activity, (-)-3-hydroxy-b-ionone and (?)-3-oxo-a-ionol may work as allelopathic substances in rattail fescue through the growth inhibition of neighboring plant species.

Controlling weeds through allelopathy is one strategy to reduce dependency on synthetic herbicides. We investigated possible allelopathic effects of rattail fescue (Vulpia myuros (L.) C.C. Gmel.). Water extract of rattail fescue inhibited root and shoot growth of cress (Lepidium sativum L.). Powder of rattail fescue also inhibited the root and shoot growth of cress in a concentration dependent manner. The effectiveness of the water extract and powder of rattail fescue on the cress root and shoot growth was not significantly different. Allelopathic active substances may be leached from the powder into bioassay medium and those substances may inhibit the cress roots and shoots. In addition, the powder inhibited root and shoot growth of lettuce (Lactuca sativa L.), alfalfa (Medicago sativa L.), Phleum pratense L., Digitaria sanguinalis L., Lolium multiflorum Lam. Lolium rigidum Gaund., Echinochloa crus-galli (L.) Beauv. and Echinochloa colonum L. in a concentration dependent manner. Therefore, rattail fescue could be useful for a weed suppressive residue or soil additive materials in the variety of agricultural settings to reduce dependency on synthetic herbicides, which should be investigated further in the field.