1. National Institute of Agrobiological Resources, Kannon-dai,Tsukuba,Ibaraki 305 JAPAN
2. School of Agriculture, Ibaraki Univ., Ami, Ibaraki 300-03 JAPAN
3. RIKEN, Koyadai, Tsukuba, Ibaraki 305 JAPAN

Rice blast resistance gene Pi-b, introgressed from indica to japonica, was narrowed its presence region to a single BAC clone (BAC 13: 180 kB). A cDNA library was constructed from green leaves of resistance cv. BL-1 with Pi-b gene. The region specific cDNAs were concentrated by hybridization with the sheared fragments of BAC 13 fixed on latex beads. 12,000 cDNA clones were hybridized to the BAC 13 and 160 times of concentration of the region specific cDNAs was confirmed. This means that survey of this region-specific cDNA population is equivalent to that of about 1.9 million of total cDNA clones. By sequencing, mutual cross hybridization, and subtraction, 17 species of genes were identified and their structures were characterized. Among them a protein kinase motif was found with a high score (>200) of homology, and showed difference in its structure between resistant and susceptible cvs. The functions of this genome region are being analyzed using our newly developed high capacity binary vector for complementation test; RAC (or pBIGRZ), which have the ability to transform large insert (>40 kb) to rice, without rearrangement of DNA. Using this vector, a sub-genome library of BL-1 was constructed at the average insert size of 42 kB and the Pi-b region was covered by its contig. Complementation test with the contig clones and the protein kinase are in progress.