GENETIC DIFFERENTIATION IN THE RICE BLAST FUNGUS REVEALED BY THE DISTRIBUTION OF THE FOSBURY RETROTRANSPOSON

Repetitive DNA sequences genetically differentiate certain host-specif ic forms of the plant pathogenic fungus Pyricularia grisea, For exampl e, high copy numbers of a sequence designated MGR586 are conserved in isolates that infect rice, In this report, we describe the molecular c haracterization 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 famil y, and gel blot hybridization analysis suggests that, like MGR586, fos bury is preferentially found in isolates that infect rice, This suppor ts the view that rice pathogens comprise a genetically distinct form o f P. grisea. We also investigated the distribution of fosbury and MGR5 86 and found that these elements are sometimes associated in the genom e, and gel blot hybridization analysis shows that restriction sites fl anking both of these elements resolve rice pathogens into similar clon al lineage groups, We conclude that the transposition of repetitive DN A sequences plays an important role in generating DNA fingerprint vari ation in the rice blast fungus. (C) 1996 Academic Press, Inc.