Analysis of Genetic Variations and Genomic Instabilities in Magnaporthe oryzae

Retrotransposons are major components of the Magnaporthe oryzae genome; their high copy number and property of stable insertion in genome make them ideal tools to develop molecular markers. Retrotransposon-based marker techniques mainly rely on the amplification of DNA sequences present between the retrotransposon termini and some component of flanking genomic DNA. In this chapter, two marker systems known as inter-retrotransposon amplified polymorphism (IRAP) and retrotransposon-microsatellite amplified polymorphism (REMAP) are described for genetic diversity studies in M. oryzae. In the IRAP method, DNA profiles are generated using outward-facing primers from two nearby retrotransposons, while REMAP produces DNA profiles from genomic segments present in retrotransposons and microsatellite repeats. These marker techniques are simple, cost-effective, and easy to develop for polymorphism studies among M. oryzae isolates, races, or populations. In addition, the chapter also describes the utility of these retrotransposon-based DNA markers to study stress-induced genomic instabilities in M. oryzae.