We determined DNA fingerprints and pathotypes on international differentials for 151 isolates of the rice blast fungus Pyricularia grisea that were collected from 15 rice cultivars at a blast disease breeding nursery in Santa Rosa, Colombia. The pathogen population expressed an extraordinarily high number (39) of pathotypes. DNA fingerprinting, using the P. grisea repetitive DNA sequence MGR586, identified 115 haplotypes that were partitioned into six discretely distinct genetic lineages. The mean genetic similarity within lineages was high, ranging from 92 to 98%. The mean similarity between lineages ranged from 17 to 85% [...]