Mapping of avirulence genes in the rice blast fungus, Magnaporthe grisea, with RFLP and RAPD markers

Three genetically independent avirulence genes, AVR1-Irat7, AVR1-MedNoi; an d AVR1-Ku86, were identified in a cross involving isolates Guy11 and 2/0/3 of the rice blast fungus, Magnaporthe grisea, Using 76 random progeny, we c onstructed a partial genetic map with restriction fragment length polymorph ism (RFLP) markers revealed by probes such as the repeated sequences MGL/MG R583 and Pot3/MGR586, cosmids from the M, grisea genetic map, and a telomer e sequence oligonucleotide. Avirulence genes AVR1-MedMoi and AVR1-Ku86 were closely linked to telomere RFLPs such as marker TelG (6 cM from AVR1-MedNo i) and TelF (4.5 cM from AVR1-Ku86). Avirulence gene AVR1-Irat7 was linked to a cosmid RFLP located on chromosome 1 and mapped at 20 cM from the aviru lence gene AVR1-CO39. Using bulked segregant analysis, we identified 11 ran dom amplified polymorphic DNA (RAPD) markers closely linked (0 to 10 cM) to the avirulence genes segregating in this cross. Most of these RAPD markers corresponded to junction fragments between known or new transposons and a single-copy sequence. Such junctions or the whole sequences of single-copy RAPD markers were frequently absent in one parental isolate. Single-copy se quences from RAPD markers tightly linked to avirulence genes will be used f or positional cloning.