Physical Mapping Of The Avirulence Gene AVR-Pii Of The Rice Blast Fungus Magnaporthe Grisea

Firstly,the two SCAR markers OPI07700 and OPM101314 was analyzed,the result show that the strains of rice blast fungus P131 and Y34 have discrepancy where the place of the SCAR marker OPM10,314. The PCR amplification products are 1314 bp in P131 andl 664 bp in Y34,but nothing in 70-15 respectivly with the primer of the SCAR marker OPM101314.Then,the 1664 bp DNA band was cloned and sequenced.The result show that the sequence of 1664 is inserting a 350 bp repeated sequence into the sequence of 1314. There is no discrepancy between the strains of rice blast fungus P131,Y34 and 70-15 where the place of the SCAR marker OPI07700. Genomic Southern Blot and BLAST using the two SCAR markers OPI07700 and OPM101314.show that the marker OP107700 is a single copy in P131 and Y34 genome,and the marker PM101314 have some repeated sequence in P131 and Y34 genome.The markers and AVR-Pii were localized near the telomere on the SupercontigIII of the Chromosome II.The avirulence gene AVR-Pii is nearer the telomere than the two markers.Chromosome walking were initiated from the two SCAR makers.Through screening the TAC genomic library and taking advantage of the rice blast DataBase, the physical map of the region of the two markers was constructed.Based on the contig maps from the chromosome walking,a minimum TAC tile containing 3 TAC clones was created.Then the physical distance between the two markers is about 90Kb.So the ratio between the physical and genetic distance is about 28Kb/cM.At the same time the genetic distance between the nearer SCAR maker OPI07700 and the avirulence gene AVR-Pii is 6.53 cM,so the physical distance is about 186Kb.With this knowledge we carry out chromosome walking toward the avirulence gene AVR-Pii. Through a minimum TAC tile containing 4 TAC clones we walking about 210Kb toward the avirulence gene.So the physical map of the region of the avirulence gene AVR-Pii was constructed.At one time, according to the rice blast DataBase we choose three locations that be likely to include the avirulence gene AVR-Pii to initiate chromosome walking.then three congtig maps were constructed.the second and the third congtig map can overlap.But the relationship of the first congtig map and followed contig maps and 4 minimum TAC tile need further research.During the chromosome walking no further marker was found.