Genetic Analysis of Field Resistance to Leaf Blast (Pyricularia oryzae) in Rice

Abstract

Rice breeders in Japan are increasingly attaching more importance to the so-called field resistance than to the true resistance in improving blast resistance of paddy rice. The former resistance is quantitative and controlled by several multiple genes or polygenes, while the latter is qualitative and affected by a single gene with major effect. Field resistance seems to be stable to changes in pathogenicity of blast fungus, but true resistance reacts specifically to different fungus strains. In the present study, two experiments were carried out to investigate the inheritance of field resistance to leaf blast in rice plants. The first experiment cosists of the analysis of genetic variations among progeny lines derived from tlvo different crosses which include Imochi 314 (a derivative line of an upland variety) and IR 279 (selected at IRRI) as donors of field resistance. The second experiment is an analysis of F₁ and F₂ diallel tables from a half diallel cross of seven cultivars or lines, i.e. Imochi 314, IR 279, an upland rice variety and four lowland cultivars differing in field resistance.