Rapid Population Analysis of Magnaporthe grisea by Using rep-PCR and Endogenous Repetitive DNA Sequences.

ABSTRACT DNA samples from Magnaporthe grisea isolates were fingerprinted by using repetitive element-based polymerase chain reaction (rep-PCR) with two outwardly directed primer sequences from Pot2, an element found in approximately 100 copies in the fungal genome. Variable length fragments, defining the sequences lying between these elements, were generated, and fingerprint patterns specific for individual strains were established. "Long PCR" conditions, including higher pH (9.2) and increased extension time (10 min) were used to amplify DNA fragments ranging from 400 bp to longer than 23 kb. Polymorphisms specific to M. grisea strains were generated, allowing inference of their genetic relationships. Segregation analysis was used to confirm single-locus inheritance for the fragments amplified by rep-PCR. Cluster analysis revealed robust groupings that corresponded to previously determined MGR586 restriction fragment length polymorphism lineages of the rice-infecting strains of the pathogen. We have also demonstrated the utility of rep-PCR to differentiate isolates that infect rice from those that infect nonrice hosts. DNA fingerprinting by Pot2 rep-PCR provides an efficient means to monitor the population dynamics of the blast pathogen. Because of the method's low cost and ease in application, it is now feasible to conduct large-scale population studies to understand the impact of host genotypes on pathogen evolution.