Experiments were performed to elucidate the biochemical nature of the diffe
rential response of resistant Vicia airopurpurea cv. Popany and susceptible
Vicia sativa cv. Yovel to the parasitic weed Orobanche aegyptiaca. Plant r
oot material was obtained by growing vetch plants in association with Oroba
nche seeds on glass microfibre filter sheets inserted in polyethylene bags
replenished by nutrient solution. Higher concentrations of bound phenolics,
free phenolics and lignin, and higher activity of peroxidase were observed
in cv. Popany roots as a result of O. aegyptiaca infection than were found
in cv. Yovel vetch. No differences in hydroxyproline-rich glycoproteins le
vels were detected between infected and non-infected roots of either vetch
cultivar. These results suggest that the resistant vetch defense mechanism
involves elevated induction of the phenylproponoid pathway upon Orobanche i
nfection, conferring mechanical and chemical barriers confronting the invad
ing parasite. (C) 1999 Academic Press.