Phenolic Compounds with Allelopathic Potential of Secale cereale L. and Raphanus sativus L. Grown Under an Agroecological No-Tillage System

ABSTRACT: The identification of compounds with allelopathic potential produced by cover crops can assist in selecting species for weed management purposes in no-tillage systems. This study aimed to identify the main phenolic compounds with allelopathic potential in the shoot of rye (Secale cereale L.) and oilseed radish (Raphanus sativus L.) cover crops, as well as evaluate whether the cultivation system and phenological stage may influence secondary metabolite production and weed emergence. Samples of the shoot of these cover crops were collected at 60, 80, and 100 days after sowing (DAS) and 15 and 30 days after lodging (DAL) under field conditions. Weed emergence was evaluated at 45, 75, and 100 DAL of cover crops. The main compounds in rye were 6-methoxy-2-benzoxazolinone (MBOA) and 2-benzoxazolinone (BOA) under monocropping and intercropping, while flavonoid quercetin was found in oilseed radish at all evaluated times. During the growing cycle, the highest contents of phenolic compounds were found at the elongation stage (60 DAS) of rye under monocropping and intercropping systems (9.33 and 8.22 mg g-1 DM, respectively) and at grain filling stage (100 DAS) for oilseed radish intercropped with rye and black oat (3.24 and 3.83 mg g-1 DM, respectively). No differences were found in the contents of the main compounds when the species was grown under monocropping or intercropping systems. A reduction in the contents of MBOA, BOA, and quercetin was observed after lodging. Weed dry matter production was lower at 45 DAL in all treatments with rye and oilseed radish residues when compared to the control. The intercropping of rye with oilseed radish is an alternative management for weed control in agroecological systems due to the physical barrier created by these species and the presence of phenolic compounds with allelopathic potential.

摘要：鉴定覆盖作物产生的具有化感潜力（allelopathic potential）的化合物，可为免耕系统中筛选杂草防控专用物种提供支撑。本研究旨在明确黑麦（*Secale cereale* L.）与油籽萝卜（*Raphanus sativus* L.）覆盖作物地上部中具备化感潜力的主要酚类化合物，并探究栽培模式与物候期对次生代谢产物合成及杂草出苗的影响。在田间条件下，于播种后60、80、100天（DAS）以及倒伏后15、30天（DAL）采集两类覆盖作物的地上部样品，并分别于覆盖作物倒伏后45、75、100 DAL开展杂草出苗情况评估。单作与间作模式下，黑麦中的特征性化合物为6-甲氧基-2-苯并恶唑啉酮（MBOA）与2-苯并恶唑啉酮（BOA）；而所有测定时段的油籽萝卜样品中均检出类黄酮化合物槲皮素。在整个生长周期中，单作与间作模式下的黑麦，其酚类化合物最高含量均出现在拔节期（60 DAS），分别为9.33与8.22 mg·g⁻¹ DM；间作黑麦的油籽萝卜以及间作黑麦与黑燕麦的油籽萝卜，其酚类化合物含量峰值则出现在灌浆期（100 DAS），对应含量分别为3.24与3.83 mg·g⁻¹ DM。当供试物种以单作或间作模式种植时，其特征化合物的含量无显著差异。倒伏后，MBOA、BOA与槲皮素的含量均出现显著下降。与对照组相比，所有施加黑麦与油籽萝卜残体的处理组，在倒伏后45 DAL时的杂草干物质生成量均更低。黑麦与油籽萝卜间作可作为农业生态系统中杂草防控的替代管理方案，其优势来源于二者构建的物理屏障以及具有化感潜力的酚类化合物的存在。