INDUCTION OF INACCESSIBILITY TO PYRICULARIA-ORYZAE BY PRE-INOCULATION OF P-GRISEA IN RICE LEAF-SHEATH CELLS

When spores of Pyricularia oryzae were inoculated onto the inner surface of detached rice leaf-sheaths after a pre-inoculation of the non-pathogenic P. grisea, penetration and intracellular hyphal growth of P. oryzae were significantly inhibited. Most epidermal cells under the appressoria degenerated. Spores of P. grisea germinated and formed appressoria 12-24 h after inoculation on the inner surface of rice leaf-sheaths. However, few infection hyphae were formed from the appressoria. The results suggest that P. grisea induces inaccessibility against a subsequent infection by P. oryzae in rice leaf-sheath cells.