An Electron Microscopic Study of the Infection of Spikelets of Rice by Pyricularia oryzae

Penetration and colonization of spikelet tissue of a susceptible line of rice. ZTS, by Pyricularia aryzae was investigated by scanning and transmission electron microscopy. Application of a modified embodding procedure in which the period of resin infiltration was extended, gave excellent fixation of the hard spikelet tissue. Conidia germinated to produce appressoria and the epidermal cell walls were penetrated within 24 h. Hyphae had colonized sclerenchyma, parenchyma, vascular bundles, andlarge trichomes within 48 h after inoculation. Invasion of the sclerenchyma appeared to occur through pit-pairs, where the host cell wall is thin. Conidiophores erupted directly from the epidermis, from minute protuberances and from large trichomes on the spikelet 4 days after inoculation.