Genetic differentiation in the rice blast fungus revealed by the distribution of the Fosbury retrotransposon.

Repetitive DNA sequences genetically differentiate certain host-specific forms of the plant pathogenic fungus Pyricularia grisea. For example, high copy numbers of a sequence designated MGR586 are conserved in isolates that infect rice. In this report, we describe the molecular characterization of another repetitive DNA sequence designated fosbury. Restriction mapping and DNA sequence analysis show that fosbury is a member of a long terminalrepeat (LTR)-containing retrotransposon family, and gel blot hybridization analysis suggests that, like MGR586, fosbury is preferentially found in isolates that infect rice. This supports the view that rice pathogens comprise a genetically distinct form of P. grisea. We also investigated the distribution of fosbury and MGR586 and found that these elements are sometimes associated in the genome, and gel blot hybridization analysis shows that restriction sites flanking both of these elements resolve rice pathogens into similar clonal lineage groups. We conclude that the transposition of repetitive DNA sequences plays an important role in generating DNA fingerprint variation in the rice blast fungus.