Inhibition of legume seedling growth by residues and extracts of quackgrass (Agropyron repens)

Aqueous extracts of A. [Elymus] repens shoots and rhizomes inhibited seed germination and root growth of Medicago sativa cv. Vernal, soyabeans cv. Corsoy 79, Phaseolus vulgaris cv. Seafarer and Lepidium sativum at concn of E. repens shoots were generally more inhibitory than extracts of rhizomes. Root and shoot DW of Phaseolus vulgaris cv. Bush Blue Lake grown under sterile conditions were reduced by aqueous extracts of shoots. Root systems were stunted and necrotic and lacked root hairs. The growth of Rhizobium sp. was not influenced by the presence of 40 or 80 mg of extracts of shoots or rhizomes/ml. E. repens may indirectly inhibit the legume-Rhizobium symbiosis by inhibiting root hair formation rather than directly inhibiting Rhizobium growth. The presence of soil microorganisms was not necessary for the development of E. repens toxicity in soil or agar. Soil microorganisms reduced toxicity of E. repens residues in soil