Abstract
The effect of the multiline consisting of a rice cultivar, Sasanishiki, and its isogenic lines on the rice blast disease caused by Pyricularia oryzae Cavara was investigated under natural conditions. The blast disease severity and the percent diseased plants in the mixtures were less than that observed in the single line plantings. The blast disease occurrence in the mixture of compatible and incompatible lines was less than that of the compatible lines mixture. Moreover, even in the compatible lines mixture, the rice blast disease severity was depressed significantly. It became apparent that a reduced inoculum density effect and a barrier effect for infection depressed the blast disease, and it was assumed that an induced resistance operated to suppress the blast disease in the Sasanishiki's multiline. Furthermore, the feasibility of using the Sasanishiki multiline of ten isogenic lines with different true resistances was effective for the control of blast diseases.
