Abstract
Bacterial leaf blight of rice plant, caused by Xanthomonas oryzae (Uyeda et Ishiyama) Dowson, is principally a vascular disease. Generally, the causal organism enters into the leaf tissue through the water-pore and multiplies in the epitheme, and then invades the vesseles through the vascular passes. The typical symptom appears thereafter.
This paper presents another mode of infection of this disease. At the seedling stage of rice plant, the causal organism enters through the stomata, and multiplies in the intercellular space of parenchyma at the coleoptile as well as the sheath of foliage leaves. However, any external symptom does not appear. Because the bacteria never invade the vascular bundles in this case. Thus, the seedlings hold the bacterium as “carrier”. It was supposed that the appearance of typical symptom would only be expected in the infection by the causal organism which is once excreted and invades the water exudation system of leaf.
The stomata are always opened (Fig. VII-1) at the coleoptile, and the semi-opening type stomata (Fig. VII-2) are distributed among the closed ones at the basal part of the sheath of foliage leaves. These Opened or semi-opened stomata are considered to be closely related to the invasion of the bacteria.
This stomatal infection is not specific phenomenon with regard to X. oryzae. The same infection and multiplication was confirmed on the “carrier” seedlings collected at farmers' nursery bed. It is suggested that the bacterial leaf blight organism usually follows this course of life cycle at the seedling of rice plant.
