Orobanche crenata is a parasitic weed that causes severe yield losses in important grain and forage legume crops.
Cereals have been reported to inhibit O. crenata parasitism when grown intercropped with susceptible legumes, but the
responsible metabolites have not been identified. A number of metabolites have been reported in cereals that have allelopathic
properties against weeds, pests, and pathogens. We tested the effect of several allelochemicals identified in cereals on O. crenata
seed germination and radicle development. We found that 2-benzoxazolinone, its derivative 6-chloroacetyl-2-benzoxazolinone,
and scopoletin significantly inhibited O. crenata seed germination. Benzoxazolinones, L-tryptophan, and coumalic acid caused the
stronger inhibition of radicle growth. Also, other metabolites reduced radicle length, this inhibition being dose-dependent. Only
scopoletin caused cell necrotic-like darkening in the young radicles. Prospects for their application to parasitic weed management
are discussed.