CLONING OF RICE BLAST RESISTANCE GENE PI-B

¹ Natl. Inst. Agrobiological Resources Kan'non-dai, Tsukuba, Ibaraki 305-8602 Japan

² School of Agric., Ibaraki Univ. Ami, Ibaraki 300-03 Japan

Rice blast resistance gene Pi-b was delineated within a single BAC clone 145G7 (180kB). A functional genome library of average insert size 30-50 kB, of the resistance cultivar BL-1 with Pi-b, was constructed using a high capacity binary vector, pBIGRZ, which can transform more than 40 kB of inserts to rice without rearrangement. The Pi-b region was covered by a contig of the components of the functional genome library. The guiding contig map of HindIII, consisting from the partial digests inserted to pBIGRZ, was constructed and was helpful for making the contig of the resistant cv. Although the both sides of the regional map was almost identical between the susceptible and the resistant cvs., the middle region showed great differences between them, suggesting a genome mobilization related to the evolution of the resistance gene. The inserts of the contig were transformed to the susceptible rice cv. Nipponbare. On average, 4-5 plants have been regenerated from a single 9 cm plate, and >10 plates of calli are transformed for a single pBIGRZ clone. There were proteins with a kinase motif and nucleotide binding motives in the region. The regenerated plants were spray inoculated with blast conidia suspension, and their resistance was assayed. The results of the complementation and the resistance-related protein structures will be presented.