Genetics of Powdery Mildew Resistance in Barley

A comprehensive, critical review on the present knowledge regarding the genetics of resistance of barley to the powdery mildew fungus is presented. The review deals with six kinds of resistance: Race-specific resistance; Mlo resistance; partial resistance; induced resistance; passive resistance; and non-host resistance. Most of the sections are subdivided into: phenotype of the interaction; resistance mechanisms; and genetics. A distinction is made between three groups of genes involved in the defense of plants to diseases: those that serve exclusively to mediate resistance; those that are mobilized to strengthen the plants' defense; and those that serve exclusively functions other than disease defense, but may bring about resistance. The more than 200 gene symbols assigned to race-specific mildew resistance genes over time are summarized and revised to 85 symbols that may be considered valid.