Inhibitory effects on Orobanche development by allelopathic
crops have been suggested before, but little was known about
the responsible metabolites. Inhibition of O. ramosa germination
was described in the wild tomato accession Lycopersicum
pennellii, suggesting that it was due to an excess of unidentified
stimulatory substances.31 Allelopathy by inhibition of O. crenata
seed germination was suggested as the mechanism responsible
for the reduction of parasitism in legumes intercropped with
fenugreek.32 Trigoxazonane was identified in fenugreek as an
active metabolite involved in the allelopathy against O.
crenata.33 Intercrops with berseem clover34 or with cereals12
reduced O. crenata parasitism in legumes, but the responsible
metabolites have not been studied so far