Biochemical factors involved in vetch resistance to Orobanche aegyptiaca

Experiments were performed to elucidate the biochemical nature of the differential response of resistant Vicia airopurpurea cv. Popany and susceptible Vicia sativa cv. Yovel to the parasitic weed Orobanche aegyptiaca. Plant root material was obtained by growing vetch plants in association with Orobanche 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 levels 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 infection, conferring mechanical and chemical barriers confronting the invading parasite. (C) 1999 Academic Press.