Abstract
The upland rice variety Sensho has a high field resistance (quantitative resistance) to leaf blast that seems to be stable in response to the c.hanges in the pathogenicity of the blast fungus (Pyricularia oryzae CAv.). Some resistant cultivars of paddy rice have been developed using varieties derived from Sensho, but their resistance levels are not as high as that of Sensho. For further use of the high field resistance, it is necessary to study the mode of inheritance of the resistance. In the present study, linkage groups of the resistance genes of Sensho were studied using linkage testers with marker genes (Table 1). Leaf blast resistance and marker genes were investigated in F3 lines derived from twelve crosses between the linkage testers and Sensho. Leaf blast resistance was estimated by nursery tests and marker genes were stuclied by using the phenotype of F3 lines in paddy fields. F3 lines were divided into three groups ; tester type group (example, la), segre-gating group (la/+) and Sensho type group (+). Linkage relation was tested by t-test for the difference of means of leaf blast score between the tester type group and the Sensho type group.
