DNA Fingerprinting with a Dispersed Repeated Sequence Resolves Pathotype Diversity in the Rice Blast Fungus.

The poor definition of pathotype variation in the rice blast fungus has historically handicapped strategies for reducing blast disease damage to the world's rice crop. We have employed a probe for a dispersed repeated DNA sequence called MGR [Hamer et al. (1989). Proc. Natl. Acad. Sci. USA 86, 9981-9985] to construct genotype-specific, EcoRl restriction fragment length profiles (MGR-DNA fingerprints) from United States field isolates of this fungus. By using a blind-test design, we demonstrated that MGR-DNA fingerprints distinguished the major pathotypes in the United States, accurately identified the pathotypes of isolates collected over a 30-year period, and defined the organization of clonal lineages within and among pathotype groups. These results resolved a lingering controversy regarding rice blast pathotype stability and illustrated new opportunities for tracking the population dynamics and evolution of this important crop pathogen.