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|環境因子對荔枝露疫病菌菌絲生長之影響=Effect of Environmental Factors on Mycelial Growth of Peronophythora Litchi
|陳隆鐘; 賴學珍; 李崇正; 鍾依紋; 安寶貞; Chen, L. C.; Lai, S. C.; Lee, C. C.; Chung, Y. W.; Ann, P. J.;
|荔枝露疫病菌; 荔枝; 菌絲生長; 溫度; 酸鹼值; 水分潛勢; 培養基濃度; 光照; Peronophythora litchii; Litchi; Mycelial growth; Temperature; PH; Water potential; Photoperiod; Concentration of medium;
|自1991年與1998年，由台灣不同地點採集罹患荔枝露疫病之果實，共分離到29 株荔枝露疫菌（Peronophythora litchii）菌株。觀察其無性世代之形態構造，胞囊為檸檬狀、 脫落性、有明顯的乳突，脫落胞囊具短梗（pedicel）；胞囊梗（sporangiophore）為多次雙歧 分枝（dichotomously branched）狀；游走胞子具雙鞭毛。本研究主要探討溫度、水分潛勢、 酸鹼值、及光照對荔枝露疫病菌菌絲生長之影響，結果顯示溫度低於4C及高於36C 時各 供試菌株都不能生長，菌絲生長最適溫為24C。在不同酸鹼值對菌株生長影響的試驗中，Ph 值於2~10時菌絲均可生長，但Ph值為4.5~8時菌絲生長情形較佳。光照實驗中，以12hr 光照╱12hr黑暗之光周期培養時菌落出現同心輪紋，且菌絲生長較完全光照處理及全黑暗 處理者為快。菌絲生長速率會隨著培養基水份潛勢的降低而減緩，當水份潛勢為-50 bar時， 菌絲則無法生長。CV-8蔬菜汁瓊脂（clarified CV-8 juice agar）培養基中的CV-8蔬菜汁濃 度在1%至50%時，菌絲均可生長，但以蔬菜汁濃度為5%時，荔枝露疫菌的菌絲生長速率 最快。
|Twenty night isolates of Peronophythora litchii were isolated from litchi fruits with downy blight symptoms, which were collected from different places in Taiwan at 1991 and 1998. Isolates of P.litchii could cause disease symptoms on mature litchi fruit via both wound and non-wound inoculation. After 4 days, the inoculated fruits were covered by a layer of white mold, which were the structures of sporangia and sporangiophores of the fungus. This indicated that the disease could develop in the field without mechanical injury. Sporangia formed on CV-8 juice agar are lemon- shaped with apparent papilla. The sporangiophores of P.litchii are dichotomously branched and the sporangia formed on a single sporangiophore are mature simultaneously. The temperatures for mycelial growth of the fungus ranged from 8 to 32 C and the optimal temperature was 24C. Mycelial growth under photoperiod with 12hr light and 12hr dark was better than those grew continuously under light or in darkness. The colonies of the fungus grown under photoperoid were with concentric circle patterns. The best conditions of pH ranges and concentration of CV-8 juice for the fungus growth were pH 4.5-8 and 5%, respectively.