Genetic Studies on Resistance of Rice Plant to Blast Fungus

Lazy-Ginga, la-isogenic line of Ginga, proved that Rb1 of Sensho linked with la had not been introduced to Ginga. Absence of Rb1 caused a significant decline of blast resistance to Ginga. From comparison of derivatives with their common parent, Sensho, it was ascertained that the present decline commenced in the early stage of the breeding program.The two blast resistance genes which controlled the moderate resistance of Ginga were assumed to be multiple alleles of the two ones other than Rb1 of Sensho.