Development of microsatellite markers for the genetic analysis of Magnaporthe grisea

An AG microsatellite-enriched genomic DNA library was constructed for Magnaporthe grisea (anamorph Pyricularia grisea), the causal agent of rice blast. Seventy-two DNA clones containing microsatellite repeats were isolated and sequenced in order to develop a series of new PCR-based molecular markers to be used in genetic studies of the fungus. Twenty-four of these clones were selected to design primer pairs for the PCR amplification of microsatellite alleles. Single spore cultures of M. grisea isolated from rice and wheat in Brazil, Colombia and China were genotyped at three microsatellite loci. Isolates from southern Brazil were predominantly monomorphic at the tested SSR loci, indicating a low level of genetic variability in these samples. However, seven alleles were observed at the MGM-1 locus in isolates from Central Brazil and at least nine alleles were detected at the same locus in a sample of Colombian isolates. Polymorphism analysis at SSR loci is a simple and direct approach for estimating the genetic diversity of M. grisea isolates and a powerful tool for studying M. grisea genetics.