Allelopathic potential of root exudates of annual ryegrass (Lolium rigidum)

Summary: A laboratory-based root exudates bioassay was conducted to assess the allelopathic potential of annual ryegrass against wheat using the equalcompartment- agar method. The effect of different growth period of ryegrass (2, 4, 6, 8, 11 and 15 days) on the allelopathic response of wheat was investigated. Results indicated that co-growth of annual ryegrass and wheat reduced the root and shoot length of wheat. Ryegrass growth for 6'8 days had the most inhibitive effect on wheat root growth. Increasing ryegrass density beyond 20 plants per beaker had no significant further effect on the allelopathic activity of annual ryegrass. To validate the allelopathic effect between ryegrass and wheat, activated charcoal was added to the growth medium (2% v/v) resulting in alleviation of the inhibition of wheat root and shoot length. Thus, the inhibition effect of annual ryegrass on wheat root and shoot length was chemically directed through its root exudates, with inhibition being greater on wheat roots than shoots.