Mapping avirulence genes in the rice blast fungus Magnaporthe Grisea
1996
Dioh, W. | Tharreau, D. | Gomez, R. | Roumen, E. | Orbach, M. | Notteghem, J.L. | Lebrun, M.H.
Fungal pathogen Magnaporthe grisea is involved in specific interactions with rice cultivars. Fungal strains with avirulence genes are nonpathogenic to rice cultivars with the corresponding race-specific resistance genes. Unraveling the molecular basis of such interactions requires the cloning of both avirulence and resistance genes. We have identified three genetically independent avirulence genes in M. grisea (AvrMedNoi-1, Avrtrat7-1, AvrKu86-1). Analysis of the segregation of avirulence toward a collection of rice cultivars suggests the occurrence of the same resistance gene in unrelated cultivars. To clone avirulence genes by chromosome walking, we constructed a partial genetic map using 77 random progeny from the backcross between isolates Guy11 and 2/0/3. This map includes 75 restriction fragment length polymorphism markers corresponding to either repeated, single-copy, or telomeric sequences and 25 random amplified polymorphic DNA (RAPD) markers. Two avirulence genes were mapped to chromosome tips (AvrMedNoi-1 and AvrKu86-1). We also identified five RAPD markers tightly linked (1-4 cM) to these avirulence genes using bulk segregant analysis. Most of these linked RAPD markers were composed of repeated sequences adjacent to single-copy sequences, which could be used to initiate chromosome walks
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