Abstract
Effects of L-methionine on the barley powdery mildew (Erysiphe graminis f. sp. hordei) were studied by electron microscopy. Barley leaves were treated with L-methionine (8×10-3M aqueous solution) 24hr before inoculation with the fungus. Primary haustoria formed in the treated leaves were examined under an electron microscope 24, 58, 96 and 168hr after inoculation. At early stages of infection, no degeneration was observed in the cytoplasm of the haustoria. Their sheath membranes were covered with electron-dense materials and their sheath matrix also contained electron-dense materials different from the former. At later stages, the haustorial content increased in electron-density, and large, more densely stained deposits were found in the cytoplasm. Epidermal cells of barley leaves treated with L-methionine before inoculation with the fungus usually became necrotic, accumulating electron -dense granules in the vacuoles. Since this phenomenon has been observed in leaves of barley varieties resistant to the barley powdery mildew, the inhibitory action of L-methionine on the fungus is thought to be due to the induction of resist ant reaction in barley leaves by L-methionine treatment. In hyphae of the fungus on barley leaves treated with L-methionine, degeneration of cell organelles could not be found, but large vacuoles with electron-dense deposits could. When barley leaves were inoculated with the fungus and treated with L-methionine 96hr after inoculation, abnormal conidia showing different stages of degeneration (partial expansion of cell wall, aggregation of the cytoplasm, and disappearance of the aggregated materials) were collected 72hr after treatment.
