GENOME ORGANIZATION OF MAGNAPORTHE-GRISEA - GENETIC-MAP, ELECTROPHORETIC KARYOTYPE, AND OCCURRENCE OF REPEATED DNAS

A genetic map of Magnaporthe grisea (anamorph = Pyricularia oryzae and P. grisea), the causal agent of rice blast disease, was generated fro m segregation data utilizing 97 RFLP markers, two isoenzyme loci and t he mating type locus among progeny of a cross between parental strains Guy 11 and 2539. Of the seven chromosomes of M. grisea, three were re solved by contour-clamped homogeneous electric field (CHEF) electropho resis, while the remaining four migrated as two doublet bands. By util izing differences between CHEF mobilities of unresolved chromosomes fr om the parental strains, Southern analysis with selected markers allow ed the chromosomal assignment of all linkage groups. A small transloca tion involving 1 marker was found in the parental strains used to prod uce the segregating population from which the map was constructed. Nin e classes of repetitive DNA elements were found in the genome of a fun gal isolate pathogenic to rice. These occurred only a few times or not at all in the genomes of isolates showing reduced virulence on rice. One repetitive DNA was shown to have structural similarity to the Alu sequences found in primates, a sequence similarity to the copia-like e lements of Drosophila, and peptide similarity to transposable elements found in Drosophila, other fungi, and higher plants.