Abstract

This study was conducted to investigate the inhibition of weed growth by different plant parts, extraction methods and cultivars of Italian ryegrass (Lolium multiflorum Lam., IRG) and determine the levels of total phenol and flavonoid contents in shoots and roots of IRG. Shoot and root length of the five weeds were inhibited to a much greater degree by fermentation extract than water, boiling water and ethanol extracts. Shoot and root length were inhibited by 96 and 94% in Monochoria vaginalis, 72 and 95% in Aeschyoa indica L., 69 and 89% in Leptochloa chinensis L. and 61 and 99% in Echinochloa crus-galli L., respectively, in response to IRG shoot fermentation extracts at 5%. In response to the same extract, Ludwigia prostrata Roxb. shoot and root length were both 100% inhibited. Inhibition of shoot and root length of the aforementioned weeds was higher in response to fermentation extracts of IRG shoots than those of IRG roots. In addition, root length was inhibited to a greater degree than shoot length in response to the fermentation extracts. There were no differences between six cultivars (Greenfarm, Hwasan 101, Florida 80, Top 90, Corwinmaster and Corwinari) on inhibition of weed growth in response to IRG shoot extracts. Total phenol contents in the shoot of six IRG cultivars were almost 1.4–2 times higher than those of roots. Additionally, the total flavonoid contents in the shoot of six IRG cultivars were 8–19 times higher than those of roots. Standard phenol compounds such as hydrocinnamic acid, caffeic acid, p-coumaric acid and ferulic acid produced similar weed inhibition. Thus, it appears that the weed inhibiting effects of IRG can be attributed to their phenol contents.