Genetics and Utilization of Pathogen Resistance in Plants.

Until relatively recently, knowledge of plant resistance to patho- gens has resulted primarily from research associated with the selective breeding of crop species. Although resistance is well described at the cellular, whole plant, and population levels in terms of genetics, histology, and associated biochemistry, a full mechanistic understanding of how pathogen resistance is mediated in plants is only now becoming feasible as a re- sult of the isolation and sequencing of severa1 putatively interacting plant and pathogen genes (see Alfano and Colher, 1996; Bent, 1996; Dangl et al., 1996; Hammond-Kosack and Jones, 1996, in this issue). Nevertheless, plant resistance genes have been used beneficially in agriculture for decades, even though their effects have not always been durable. This review provides a short and selective overview of the genetics of pathotype-specific resistance in plants, its past utilization in crop improvement, and some indications of how recent ad- vances may impact the future. Reference to data obtained from investigations with a few well-studied host-pathogen combi- nations (Table