ABSTRACT
The rapid and localized pathogen-induced synthesis of phytoalexins is thought to play an important defensive role in the early response of many plants to infection by potential parasites (Dixon and Lamb, 1990). In susceptible hosts, the growth of biotrophic fungal pathogens is unrestricted, and a compatible host-parasite interaction may develop given favorable environmental conditions. Responses usually associated with resistance are not entirely absent, but rather are not expressed soon enough or with sufficient magnitude at the infection site to be effective (Kuć and Rush, 1985). Presumably the necessary elicitor signals are either not released in sufficient magnitude or are not recognized sufficiently rapidly by the plant.
