Molecular Control of Disease Resistance in Plants

Abstract

Resistance to disease is a more common phenomenon in plants than susceptibility. In many cases the inheritance of disease resistance has been established in common crop plants. Nevertheless, in most cases the gene products from the host and the parasite governing the outcome of the interaction are unknown. Susceptibility to disease must necessarily be the result of molecular interactions between the host and its parasite. Expression of resistance on the other hand could conceivably include a wide range of phenomena including the mechanical exclusion of the parasite. Thus, a study of the susceptible interaction is warranted. For this reason we have chosen to examine the biochemistry of a host-parasite system in which the following criteria were met:

• 1. The majority of the disease symptoms are caused by a toxin produced by the parasite. Thus, the other complexities in the host-parasite system are eliminated and the biological activity of the toxin can be studied.

• 2. The toxin is host-specific (host range identical to that of the parasite).

• 3. The host plant has a broad range of toxin-sensitive and toxin-insensitive clones.

• 4. The toxin can be isolated, characterized and labeled with radioisotopes.