Plant Resistance Genes for Fungal Pathogens - Physiological Models and Identification in Cereal Crops

The complex biological phenomenon “resistance” can be reduced to single Mendelian traits acting on both the plant and the pathogen side in a number o f pathosystems. According to the “gene-for-gene hypothesis”, the outcome o f a plant/pathogen interaction in these cases is in­ compatibility if a plant carrying a particular resistance gene and a pathogen with the comple­ mentary avirulence gene meet. This suggests a causal role o f resistance genes in a recognition process initiating active plant defense responses. Fundamentally different strategies are followed to identify these genes molecularly depending on the plant and pathogen species involved. Fun­ gal diseases o f crop plants, especially those o f cereals, cause dramatic yield losses worldwide. It is assumed that a molecular characterization o f plant genes conferring resistance to fungal pathogens will lead to a better understanding o f the plant defense system in general permitting the development o f new methods o f crop plant protection.