Curvularia lunata菌之生理性質及其對水稻病原性之研究

Abstract

1.Curvularia lunata菌對水稻病原性，在葉片上形成褐色之紡錘形病斑，其分生胞子呈黑色，末端細胞較中間者為淡，具有三個隔膜，第二個細胞較其他細胞大而黑，且彎曲，以測微計測定100個胞子之結果，其平均值為24.3×10.8μ。 2.溫度試驗結果顯示適宜於本菌之發育溫度在30℃左右，溫度高達40℃或在5℃之低溫時，病菌則停止發育。當溫度由10℃~30℃時，C. lunata菌之發育隨溫度之增高而增長，但當溫度高於30℃以上時則本菌之發育隨溫度之增高而降低。本菌係一耐高溫菌，其致死溫度高達62℃。 3.C. lunata菌對pH值之適應範圍甚廣，由pH5.0~12.0均可生長。惟在12.0時則發育不良，至pH12.3時則本菌停止生長。對本菌最適宜之pH值為7.0~8.0。 4.最易為C. lunata菌利用之碳素源為Glucose, Fructose, Dextrin, Sucrose及Maltose，其次為Galactose, Lactose, Xylose及Raffinose，不易利用之碳素源有Inulin, Mannitol, Sorbose及Cellulose。 5.供試之氮素源中，Peptone, Asparagine, Asparticacid，及Glutamine對C. lunata菌之生長係良好之氮素源，其次為Urea及Leucine。最差之氮素源為NaNO3，Methionine及(NH4)2 SO4。 6.C. lunata菌由傷痍感染時發病率甚高，若以健全葉片接種時則感染率較低。故本菌對水稻之主要感染途徑可能係經由傷痍感染。 1. The fungus, Curvularia lunata, was pathogenic to rice plant. The lesion caused by this fungus on rice plant was similar to which caused by Pyricularia oryzae. Its conidia are dark, more or less fusiform, 4 celled, end cell lighter, typically bent or curved, with one of the central cell enlarged. The size of the fungus measured 24.3 x 10.8 in the average of 100 spores. 2. The effect of temperature on development of the fungus showed that its optimum temperature being around 30°C and there were no development of the fungus when the temperature were at 5°C and 40°C. Simultaneously, this fungus was shown to be highly tolerable to high temperature as its thermal death point was as high as 62°C. 3. The effect of the pH value on development of Curvularia lunata showed that the optimum and maximum value for the fungus were pH 8.0 and 12.3, respectively. 4. The ability of C. lunata to utilize certain carbon compounds were in many patterns. This fungus well utilized glucose, fructose, dextrin, sucrose and maltose. The carbon compounds such as inulin, mannitol, sorbose and cellulose were poor carbon sources for the development of the fungus. 5. Among the various nitrogen compounds tested, peptone, asparagine, aspartic acid and glutamine were the good sources for the development of C. lunata while the sources of NaNO3, methionine, and [(NH4)2 SO4] were the poor ones for the fungus. 6. So far as the inoculation concerned, wound infection showed high percentage of infection indicating that the main pathway of infection of the fungus to rice plant might be through the wounding of the plant.