土壤溫度對蘿蔔黃葉病的影響

Effect of Soil Temperature on Radish Yellows Pathogen

蘿蔔黃葉病的發生程度，深受環境因子中溫度的影響。根據試驗結果顯示，黃葉病在25±3°C時發生最為嚴重，而較高或較低的溫度皆會使病害降低。經進一步探討溫度對病原菌的影響，發現溫度愈低，病原菌的成活率愈高；在24－28°C最適於病原菌的生長。測定胞子發芽結果，雖在水瓊脂（water　agar）上，胞子及厚膜胞子最適溫略有差異（前者28°C，後者24°C），但發芽管長度均以28°C最為適合；土壤厚膜胞子之測定結果亦以28°C為較適合發芽之溫度。

Disease incidence of radish yellows caused by Fusarium oxysporum f. sp. raphani Kend et Snyder., was influenced by change of temperature. In our experiments, we found that the optimum temperature for disease development was 25±3°C, and the disease severity was significantly decreased by lower or higher of temperature. The pathogens grow on Czapek's agar at 8-36°C, with optimum at 20-28°C. It was found that survival of the pathogen in soil gave longer period in lower temperature than higher temperature. The optimum temperature (28°C) for germination of conidia and chlamydospore was hardly any different in soil or on water agar, except 24°Cwas better for germination of chlamydospore on agar, but 28°C still was best for germ tube development.