Abstract
Pathogens and insects seem to attack unhealthy plants, and the trace of unhealthy growth may remain in the plant organs after attack. Grain yield of rice plants infected with bacterial grain rot (Pseudomonas glumae Kurita and Tabei) was 85% of the control. In the infected rice, the number of panicles per unit land area and that of spikelets per panicle were the same as those in the control and 1000 grain weight was 8% heavier than in the control, but the percentage of ripened grains was only 57% of the control. The percentage of ripened grains on the stem (including both main stem and tillers) in infected rice hill varied with the stem ranging from 14 to 89%, even among those from the same seed. Grains of infected rice contained a large amount of nitrogen than the control. In the infected rice hills, the number of growing crown roots was almost the same as that in the control, but the number of stunted roots was higher than that in the control. The percentage of stunted crown roots in the infected rice hill was higher than that in the control already at three weeks after transplanting. Infection of rice plants with bacterial grain rot is recognized as a depression of grain ripening after heading, but the symptom of this disease seems to appear as the stunted root growth at an early stage before heading.
