施用貝芬替、賓克隆和益達胺對土壤細菌族群結構的影響

Abstract

本研究針對台灣常用的三種農藥貝芬替、賓克隆和益達胺，探討施用後其對土壤中細菌族群結構的影響。本實驗土壤採自苗栗縣大湖鄉觀光草莓園外埔砂壤土系，於兩種孵育溫度下(25和40 ℃)分別添加10和100 mg Kg-1不同濃度的貝芬替、賓克隆和益達胺於暗室進行孵育，並在不同時間點取出土壤，以HPLC分析農藥殘量，同時進行土壤總DNA萃取。再藉由聚合酶鏈鎖反應(Polymerase chain reaction, PCR)放大細菌族群的16S rDNA片段，配合變性梯度凝膠電泳(Denaturing gradient gel electrophoresis, DGGE)分析並觀察施用貝芬替、賓克隆和益達胺對土壤中細菌族群結構的影響，最後利用軟體分析施藥後各時間點土壤細菌族群結構的相似度。研究結果顯示，以一次動力方程式計算添加10 mg Kg-1貝芬替在25和40 ℃孵育時的半衰期分別為105和103天，而添加100 mg Kg-1 處理者，因在120天的實驗期間內無明顯減少情形，故無法計算其半衰期。由殘量分析結果發現高濃度處理者的降解速率比低濃度處理者慢，且在40 ℃下孵育的降解速率比25 ℃者快，這是因為高濃度處理有較明顯對細菌的抑制，也就抑制了細菌對農藥的降解。由PCR-DGGE的指紋圖譜發現，土壤在不同孵育溫度處理會得到不同的細菌族群組成結構，且有添加農藥處理者的亮帶數目明顯比沒有添加農藥處理者少，這顯示土壤中有些細菌族群會因為施用農藥而被抑制或者殺死。隨著孵育時間的增加，PCR-DGGE指紋圖譜上亮帶的消長現象可知，部分細菌族群不會受到農藥的影響，部分細菌族群因受到抑制或毒害而消失，部分細菌族群會被誘導而出現。

The effect of fungicides carbendazim, pencycuron and insecticide imidacloprid on soil bacterial community structure was studied. The WaiPu sandy loam soil used in this experiment was sampled from strawberry field locate in Da-Hu of Mia Lei County. Degradation rate of pesticides were determined by the residues of pesticides in soil which sampled at different intervals. The variation of bacterial communities during incubation was performed with counting the 16S rDNA band on denaturing gradient gel electrophoresis patterns. From the result, the half-life of 10 mg Kg-1 carbendazim in soil incubated at 25 and 40 ℃ was 105 and 103 days, respectively. And there were no degradation found in a concentration 100 mg Kg-1 at the same incubated temperature. It showed very slow dissipation rate than the other two pesticides in the same treatment. Meanwhile, all three pesticides showed slower dissipation rate in sterile soil than in no sterile soil. It means microbes involved in the dissipation of these three pesticides in soil. The DGGE fingerprint showed that some soil bacterial communities would be inhibited, some would be introduced and some would not be affected by treated with pesticides carbendazim, pencycuron or imidacloprid. Besides, the DGGE fingerprint also showed that the soil bacterial community structure would be different at different incubation temperature.