Isolation of TC/AG repeat microsatellite sequences for fingerprinting rice blast fungus and their possible horizontal transfer to plant species.

Genome fingerprinting has been a major role in characterization of population structure and analysis of the variability in phytopathogenic fungi. In order to characterize Korean rice blast fungal isolates, the genomic DNAs were digested with AluI endonuclease and subsequent PCR amplifications using random decamer primers with combinations of microsatellite primers had been carried out. This Alu-Inter SSR technique revealed high polymorphism among the Korean blast fungal isolates. Then, fragments from the Alu-Inter SSR analysis were isolated to be used as probes in Southern hybridization, which also revealed high polymorphism between isolates to distinguish individuals. The sequences of the isolated fragments contained TC/AG tandem repeats interspersed with a 30 bp direct repeat. In gel blot analysis, the isolated TC/AG repeat microsatellite sequences were proved to be useful for characterizing the isolates in blast fungi in addition to the conventional MGR (Magnaporthe grisea repeat) probes. One interesting point was that the rice blast fungus derived TC/AG repeat microsatellite sequences were abundant in non-rice blast fungi and plant species, but not in other fungi and yeasts. A discussion on the possible horizontal gene transfer between phytopathogenic fungi and host plants is presented.