Partial mapping of avirulence genesAVR-PiiandAVR-Piain the rice blast fungusMagnaporthe oryzae

Two avirulence genes AVR-Pii and AVR-Pia in the rice blast fungus Magnaporthe oryzae were mapped using a cross between fertile isolates Y93-164a-1 and Y93-165g-1. Thirty-one restriction fragment length polymorphism (RFLP) markers from existing M. oryzae genetic maps were used to construct a partial genetic map based on 52 randomly selected progeny from the cross. Genetic linkage between the RFLP markers and AVR-Pii or AVR-Pia was determined. Gene AVR-Pii was found linked to two markers on chromosome 7 in the Guy11 × 2539 genetic map and to one independent marker on the CHNOS37-1-1 × CHNOS32-2-4 genetic map. Gene AVR-Pia was linked to three markers on chromosome 5 and one marker on chromosome 7 in the Guy11 × 2539 genetic map. Among 52 progeny, AVR-Pii was completely linked to G131R, a marker closely linked to RFLP telomeric marker 13 on chromosome 7, suggesting that AVR-Pii has a subtelomeric location as seen in many other M. oryzae avirulence genes.