Pathological studies on rice blast, caused by Piricularia oryzae

II. On the mode of infection of the pathogene

Abstract

According to the inoculation experiment with Piricularia oryzae to the young blade of adult-tillering-rice, the fungus forms at first the brown coloured appressorium on the host, and then enters the epidermal cell piercing through the outer layer of the epidermal membrane, if the latter is not so highly silicified as that of the dumb bell shaped rice-cell, the various trichomes and the papillalike bodies of the outermost layer of epidermis.
The motor-cell and the accessory cell of the stoma seem to be the portions most easily infected.
In the case of the inoculation to the base of the ear-Hokubi-when it is just the time of earing, the fungus enters the host cell as in the case of the blade but with difficulty. Among the epidermal cells of the inoculated portion, the long cells situated on the upper parts of the assimilating parenchyma near the nodes of the racheae and the cells of the bracts projected from the basal nodes of the ears are observed to be the portions rather easily infected.
The penetration begins with the emergence of the slender penetration hypha at the central part of the under surface of the appressorium. Then the infection hypha pierces the outer layer of the epidermal membrane and enters the cavity of the affected cell. When the hypha reaches the inner surface of the membrane, soon forms a small vesicle. Sometimes the callosity may be observed at the inner surface of the pierced membrane. After this, vegetative hyphae may be formed branching from the vesicle or by the conversion of the latter.
The morphological and anatomical structure of rice, especially of its epidermis has been described.