REARRANGEMENTS AT A DNA FINGERPRINT LOCUS IN THE RICE BLAST FUNGUS

Populations of the rice blast fungus, Magnaporthe grisea, can be sorte d into clonal lineages based on restriction fragment length polymorphi sms (RFLPs) detected with the repetitive DNA sequence MGR586. Mechanis ms that produce DNA-fingerprint variation among lineages, are not know n. In the process of analyzing the meiotic segregation of MGR586 RFLPs we identified a novel polymorphism, called MGR586-P2, in one member o f a sister-spore pair from a complete tetrad. Molecular cloning reveal ed that P2 was generated by a nearby insertion of a novel, long-termin al-repeat (LTR)-containing retrotransposon. Genetic analysis showed th at P2 and its progenitor polymorphism (P1) are alleles of a single pol ymorphic locus termed MGR586-PL (PL). Surprisingly, we found that a st rain harboring PL recurrently produced clonal descendants harboring P1 , P2 and possibly a third allele designated P3. PL is not located near a telomeric region. Our results show that some DNA-fingerprint loci m ay be hypervariable and undergo recurrent rearrangements. These findin gs have implications for interpreting DNA-fingerprint profiles from M. grisea populations.