Identification and isolation of blast resistance genes in three indica-type rice varieties

Two methods were used to identify blast resistance genes in indica-type varieties and isolate the genes found: one was an inoculation of F-3 lines between indica-type and japonica varieties (Suweon 262 x Reimei) with a common fungus strain (Ken 54-20) and a fungus strain having many virulence genes (Ao 14-20) and selection of F-3 lines showing different reactions to the two fungus strains, and the other was selection of F-3 lines showing a 3 : 1 segregation ratio in the hybrid (Norin 29 x Hokuriku 129 and Norin 22 x Sifeng 43) for Ken 54-20. The former method was used to identify and to select the resistance gene brokendown by Ao 14-20 having several number of virulence genes, The latter was to identify and isolate all major genes included in the resistant variety. It was demonstrated that Suweon 262 had Pi-i and an unidentified major gene and at least a minor one, and Hokuriku 129 had two major genes, Pi-i and Pi-b : Sifeng 43 had one major gene Pi-b and at least one minor gene, Minor genes disturbed the isolation of major genes in cross combinations of Suweon 262 x Reimei and Norin 29 x Hokuriku 129, It was considered that Hokuriku 129 is heterogeneous at least for Pi-i and Pi-b.