INHERITANCE OF RESISTANCE TO BLAST DISEAS E IN UPLAND RICE NORIN-MOCHI-4

Since Upland Rice Norin Mochi (glutinous) 4 was known to rice breeders to show the highest field resistance to blast disease, the inheritanc e of resistance was analyzed in the cross between Upland Rice Norin Mo chi 4 and the susceptible lowland rice cultivar Koshihikari. The conti nuous variations of resistance in the various hybrid populations sugge sted that the resistance was inherited quantitatively and controlled b y many genes with individually small effects. However, the statistical method to estimate the number of involved genes from the components o f variation failed due to some discrepancies between the sizes of the culculated and estimated variances. Two other methods were used to est imate the number of genes. The proportions of susceptible lines in the hybrid populations suggested the contribution of four genes to the re sistance. Partitioning the resistance degrees in the hybrid progenies by phenol staining on palea and lemma revealed that the resistance was conrolled by at least four genes, one of which was linked to the phen ol reaction gene.