Determinação da capacidade alelopática de extratos obtidos de azevém (Lolium multiflorum) sobre a germinação e crescimento de picão-preto (Bidens pilosa) e Capim annoni-2 (Eragrostis plana)

Abstract

The objective of this study was investigated the allelopathic potential of extracts obtained from the aerial portion of ryegrass (Lolium multiflorum) and their inhibitory effect on the germination and early growth of blackjack (Bidens pilosa) and annoni-2 grass (Eragrostis plana). Dried ryegrass material (aerial parts and roots) was ground and subjected to exhaustive cold extraction with four solvents of increasing polarity: hexane, ethyl acetate, methanol, and water. Subsequent bioassays employed the ethyl-acetate extract from aerial tissues (AE-A), a medium-polarity solvent that favors phenolic metabolite recovery. Tests were run in a BOD (Biochemical Oxygen Demand) chamber at 100 mg L⁻¹, 200 mg L⁻¹, 300 mg L⁻¹, 400 mg L⁻¹, and 500 mg L⁻¹. The extract significantly affected: IVG (germination speed index), TMG (mean germination time), TPAM (mean shoot length), and TRM (mean root length) in Eragrostis plana seedlings; and IVG, TMG, and TRM in Bidens pilosa seedlings. Overall, annoni-2 grass was more sensitive to the ryegrass ethyl-acetate extract than blackjack. These results indicate that the extract can suppress the emergence and initial development of both weed species, offering a potential plant-based tool for weed management in cropping systems that are not affected by ryegrass allelopathic interference.