Katsumi AKUTSU, Koji AMANO and Nagahiro OGASAWARA: Inhibitory Action of Methionine upon the Barley Powdery Mildew (Erysiphe graminis f. sp. hordei) I.

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1 Katsumi AKUTSU, Koji AMANO and Nagahiro OGASAWARA: Inhibitory Action of Methionine upon the Barley Powdery Mildew (Erysiphe graminis f. sp. hordei) I. Microscopic Observation of Development of the Fungus on Barley Leaves Treated with Methionine Abstract This paper deals with the results of experiments, in which excised first leaves of barley seedlings were inoculated with conidia of race 9 of Erysiphe graminis f. sp. hordei, the basal parts of the leaves being inserted in solutions of L-, DL-and D-me thionine. On barley leaves treated with methionine, germination of conidia and penetration of the fungus into the epidermal cell wall were as good as on control plant. Inhibition of the fungal developmemt became apparent only after the penetration process started. The form of the primary haustoria showed anomalies in reduced number and abnormal elongation of projections and the absorbing function fell remarkabley. Formation of the secondary and subsequent haustoria was reduced, but the ratio of haustoria to hyphal cells per colony was higher than control. When the leaves were treated with L-methionine before inoculation, colony development was very poor and formation of conidiophores and conidia did not occur. In the treatment with D-methionine, the produced colonies were observed to form single conidiophores which produced conidia. On the leaves treated with methionine 2 or 3 days after inoculation, conidiophores and conidia were observed to develop but they were scanty. In the treatment with L- and DL-methionine after sporulation commenced, namely 5 days after inoculation, long chains of unreleased conidia numbering twenty or more were found on conidiophores. Germination and appressoria formation of such conidia were poor as compared with control and colony formation by them was very rare. (Received July 25, 1976)

2 Table 1. Germination and formation of appressoria and primary haustoria on barley leaves treated with amino acids a) Ratio of appressorium-forming conidia to germinated conidia. b) Ratio of conidia forming primary haustoria to total inoculated conidia.

3 A B C D Fig. 1. Primary haustoria formed on barley leaves treated with L-, DL- and D-methionine. A: L-Methionine; B: DL-Methionine; C: D-Methionine D: Control Table 2. Length of hyphae per colony nourished by the primary haustorium on barley leaves treated with amino acids during 58 hours after inoculation a) Number of projections per primary haustorium.

4 Table 3. Number of haustoria per colony formed on barley leaves treated with amino acids, 72 and 96 hours after inoculation Table 4. Length of hyphae per colony developed on barley leaves treated with amino acids during 72 and 96 hours after inoculation

Ann. Phytopath. Soc. Japan 43 (1). January, 1977 37 Table 5. Formation of conidiophores and conidia on barley leaves treated with amino acids a) Number of conidiophores per colony.

5 Ann. Phytopath. Soc. Japan 43 (1). January, Table 5. Formation of conidiophores and conidia on barley leaves treated with amino acids a) Number of conidiophores per colony. Barley leaves were treated with amino acids 48 hr after inoculation and observed 24hr later. b) Number of conidia-forming colonies per leaf. Barley leaves were treated with amino acids 72hr after inoculation and observed 24hr later. B C D Fig. 2. Long chains of conidia on barley leaves treated with L-methionine. A: L-Methionine( ~97), B: L-Methionine( ~420) C: Control( ~97), D: Control( ~420)

6 Table 6. Inoculation test with conidia formed on barley leaves treated with L- and DL-Methionine a) Ratio of appressorium-forming conidia to germinated conidia. b) Ratio of colony forming conidia to total inoculated conidia.

7 Ann. Phytopath. Soc. Japan 43 (1). January, Covey, Jr.R.P. (1971). Phytopathology 61: Dekker, J. (1969). Neth. J. Pl. Path. 75: Kuc, J., Williams, E.B. and Shay, J.R. (1957). Phytopathology 47: Papavizas, G.C. and Davey, C.B. (1963). Phytopathology 53: Perrin, D.R. and Cruickshank, I.A.M. (1965). Aust. J. Biol. Sci. 18: Spoerl, E., Sarachek, A. and Smith, S.B. (1957). Am. J. Bot. 44: van Andel, O.M. (1966). Annu. Rev. Phytopath. 4:

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