GENETIC-ANALYSIS OF DNA FINGERPRINTS AND VIRULENCES IN ERYSIPHE-GRAMINIS F SP HORDEI

A DNA probe, E9, which has been used extensively in population genetic studies of the barley powdery mildew pathogen, Erysiphe graminis f.sp . hordei, was shown to be homologous to dispersed sequences in the gen ome of this fungus. In a cross of the isolates CC52 and DH14, fragment s with homology to E9 mapped to six clusters of loci. Avirulences matc hing five resistance genes in barley were controlled by single genes, in accordance with the gene-for-gene hypothesis, while avirulence matc hing a sixth resistance gene, Mla13, was controlled by two genes. A ge ne which controls the response to a fungicide, ethirimol, was not link ed to any other gene. In all, seven linkage groups, comprising 22 loci , were detected. The results indicate that E9 can be used to identify members of a clone of E.g. f.sp. hordei, but should not be used for qu antitative population genetic analysis.