Host-Derived Acetogenins Involved in the Incompatible Parasitic Relationship between Cuscuta reflexa (Convolvulaceae) and Ancistrocladus heyneanus (Ancistrocladaceae)*

: The twining parasitic plant Cuscuta reflexa is able to attack the tropical liana Ancistrocladus heyneanus by invading the stem tissues and forming haustoria that penetrate the vascular bundles of the host. Subsequent reactions by the host, including phytoalexin production and hypersensitive reactions, lead to a degeneration of the parasite's haustonria and eventually to the abortion of parasitic tissues. In experiments with callus cultures of both plants, acetogenic secondary metabolites produced by the host, in the first line the naphthoquinone plumbagin, are demonstrated to be major antipathogenic factors involved in this incompatible relationship.