Approaches and progress in the molecular cloning of plant disease resistance genes.

TLDR: Unlike chordate animals, plants have not evolved a single primary mechanism for dealing with a broad spectrum of pathogens, so they have resorted to a variety of structural and biochemical defense mechanisms more or less tailored to individual pathogens.

Abstract: Unlike chordate animals, plants have not evolved a single primary mechanism for dealing with a broad spectrum of pathogens. Instead, plants have resorted to a variety of structural and biochemical defense mechanisms more or less tailored to individual pathogens. Many of the structures and compounds associated with the resistance of plants to pathogenic infection have been identified and studied for decades by plant pathologists, physiologists and biochemists. Similarly, genetic variation has been noted between plant lines in resistance to particular plant pathogens or pathogen races for most of the plant::pathogen interactions that have been studied. And, in over 200 cases, the differential susceptibility has been attributed to allelic variation at major resistance (or “R”) genes. Surprisingly, in only two cases have inherited resistances been clearly associated with the presence or absence of an identified biochemical resistance activity, and neither of these seem to be a common mechanism of resistance (1,2).